US3598980A - Method of and apparatus for determining area gravity - Google Patents

Abstract

Gravity profiles are smoothed by differing smoothing intervals. Several of the smoothed profiles are then combined, or averaged, to form an averaged area gravity value. The averaged area gravity values are subtracted one from another to generate a plurality of difference area gravity values. Each of these difference area gravity values accentuates an anomaly in a different depth range.

Description

United States Patent {72] Inventors mm, L. Lawrence Riverside, Cont: Gllert W. EIa't, Doll, Ten; John A. Lester, Dallas. Ten: Alien W. Musg'ave,

Dell-,Tex.

[2!] Appl. No. 860,117

[22] Filed Sqt. 12, I969 453 Patented A... 10. 1971 [73) Auignee MolllOilCorporIbn cmndflplcltioaser. No. 330,413, Dee. 13,1963, in llllndoned.

[S4] ME'I'IIODOF AND APPARATUS FOR DETERMINING AREA GRAVITY 14 CHI, 12 Driving 1 [$21 US. Cl. 235/181, 235161.13, 235/l64 5n 001v 7/06,

558;: 5/34, 606g ms [$01 l 'leldoiseuch zas/m,

182, I84, 153,164, 6L6; 340M725; 324/IO [56) Relerences Cited UNITED STATES PATENTS 2,80l,794 8/1957 Garvin et a]. 235/616 2,959,35l l l/l960 Hamilton et al. 235/153 3,112,397 ll/l963 Crook 235/l8l 3,256,480 6/1966 Runge et al, 324/l0 3,284,763 ll/l966 Burg et a]. 235/l81 X 3,3 [9,226 5/1967 Mott el al. 235/164 X Primary Examiner- Malcolm A. Morrison Amlrlant Examiner-Felix D. Gruber ABSTRACT: Gravity profiles are smoothed by differing smoothing intervals. Several of the smoothed profiles are then combined, or averaged, to form an averaged area gravity value. The averaged area gravity values are subtracted one from another to generate a plurality of difference area gravity values. Each of these difference area gravity values accentuates an anomaly in a different depth range.

PATENTEDAUBIOIQH 3,596,980

SHEET 03 0F 10 Fig. 2

5 6 .H I a x x. u u o p q I o 0 0 o o o o o o o o o o o a o 0 o o o o O O O o o o o o a 0 0 o o o o 6 o o o o O o o o i c O O Q o o o o l I L1 1 9 o o o I T T o o 0 IO 0 O o O J). o o o O l 5 n I I O 0 0 r. o o o T 5 o o o 0 0 o O Q o 0 l3 0 T o 0 o o l6 0 o o o O 0 o 0 '70 O c o o o o o o 0&1 J r-\ 90w) Fig, 4

D Defence PATENIEU Aucmml 3.598.980

sum 05 0F 10 mreeanoa PATENIED AUBI olsn sum as or 10 PATENTEU AUG I 0 I971 SHEET 01 or m 5% i a 5 H PATENTEDMJGIOBII 3.598.980

saw 090$ 1o Fig. 9

4 I Instruct ions '26 Control I' Unit 1 I25 I Input Output Arithmetic Units I Internet Storcqo Unrt Putufiand 24/ an we ona Reports DATA now PATH murauc'non rLow---- PATH F ig, l0

METHOD OF AND APPARATUS FOR DETERMINING AREA GRAVITY This case is a continuation of application Ser. No. 330,413 filed Dec. 13, I963, now abandoned.

This invention relates to a method of and means for transforming gravitational potentials obtained over selected areas into forms which accentuate anomalies and provide information as to the depths of the structures giving rise to them.

In accordance with application Ser. No. 669,3 l4 filed Sept. 20, 1967 which is a continuation of Ser. No. 214,973 filed Aug. 6, 1962 and now abandoned, for Method and Means for Treating Gravity Profiles," filed by one of the joint inventors of this application, gravity profiles are treated with a plurality of selected averaging operators and difference profiles generated by subtracting one from the other in a predeten mined manner. While the treatment of gravity profiles as disclosed in said application has proved advantageous in revealing the nature and depth of masses giving rise to gravity anomalies, something has been left to be desired. More particularly, these anomalies are generally not isolated symmetric masses, but rather are elongated and of changing width. Therefore, the area, extent and trends of these anomalies are not immediately evident by comparison of profiles, whereas a study on an area basis does disclose these features.

Accordingly, by utilizing the gravity values at all observation stations on a gravitational map and including interpolated values when needed for developing a plurality of additional gravitational maps each having gravity values averaged over a different selected area, maps of difference values may then be developed which will better display anomalies due to the masses of the character above mentioned.

In accordance with the present invention, the information from which the gravity map has been drawn is treated in a manner greatly to enhance the identification of the anomalies, not only to make them more readily apparent, but also to yield additional and more definitive information from them.

The foregoing and other objects, features and advantages of the present invention will be better understood from the following more detailed description in conjunction with the drawings in which:

FIG. I shows an untreated gravity map;

FIG. Ia shows a flow sheet of the process of the invention;

FIG. 2 shows a set of averaging operators;

FIG. 3 shows a gravity map which has been treated in accordance with this invention;

FIG. 4 shows a gravity profile;

FIG. 5 shows a portion of the analog equipment used in practicing this invention;

FIG. 6 shows another portion of the analog equipment used in practicing this invention;

FIG. 7 shows still another portion of the analog equipment used in practicing this invention;

FIG. 8 represents all of the analog equipment used in practicing the present invention;

FIG. 9 is a schematic showing of digital data processing used in practicing the present invention;

FIG. I0 shows punched cards on which gravitational data is punched;

FIG. ll shows in more detail the digital data processing used in practicing the present invention.

Referring now to the drawings, there has been illustrated in FIG. 1 a gravity map typical of those made in the field for the determination of gravity anomalies from which information can be gained as to the nature and character of subsurface masses giving rise to them.

In the following description, reference will be made to gravity values appearing on the map of FIG. I and on other selected portions thereof later illustrated, it being understood, of course, that the gravity values themselves are of prime importance. The gravity values also may be utilized directly in accordance with the following explanation for their modification and treatment in digital form.

There has been illustrated in FIG. 2 a set of averaging operators, each definitive of a selected and different area. and each symmetrical about a common point. Thus, each averaging operator. taking into account a selected area of the surface, will provide better information as to the nature and character of the masses giving rise to gravitational anomalies.

The first operator is designated r---| MM) 7, V hich is to be read as the average value at a point .r,y of the gravity 3 measured over a square 21 on each side and centered about the point any). Similarly, the remaining operators Mm) represent average values of gravity at the same point x, y but in respect to larger squares the respective sides of which correspond to 41, IT and 161. For each operator, T is taken as the separationdistance between rows and columns of equally spaced observation points of the gravity potential along the periphery of the averaging area which, in each case, is shown as asquare in FIG. 2.

A derivation of these operators will be described in substantial detail subsequently. At this point, one need only appreciate that the operators may be obtained by first individually integrating with respect to distance all gravity profiles for the particular operator square. The integrated values for the profiles are then divided by the distance of the square side.

The small circles of FIG. 2 identify the gravity values and in some cases. these may correspond with observation points, though in FIG. 1 these points have been omitted. In most cases, the map of FIG. I will have provided a grid on which the points will be spaced as rhown in FIG. 2 and in respect to which there will be provided gravity values, though interpolated from the actually observed gravity potentials, if necessa- It will be observed that the gravity values represented by the small circles on the averaging operators of FIG. 2 may be identified by the several rows numbered on the y-axis respectively l--l7 and the columns along the .x-axis identified respectively as A-().

As already explained, the operator l l a( I means that the values of gravity lying on the periphery of and within a square whose sides are 2T long and including the symmetrical point L9 will be averaged together to provide a single value of gravity potential. The operator l" 'l a (m) w, to the tight until the outer boundary of the averaging operator 11!) coincides with the right-hand limit of the gravity map. The operator is then shifted in discrete stepsdownwardly from its first location at I, to a new location at l,I0, and the foregoing operations repeated until the whole map has been covered, i.e., until the lower boundary of the averaging operator F' 1 ml) coincideswiththebottornedgeofthe map.

In FIG. I the boundary lines have been provided for convenient reference, it being understood that the map itself will becoll'derablylargerandthatonlyasignificantportionhas been illustrated in relationtoFlG.3latertobedeecribed.

It istobe understood thatuponcornpletionofthe scanning oftbe map with the averaging operator l i 00ml) as first described, there will be obtained new values of the gravity potential from which a new map may be drawn.

The foregoing operations are then repeated in succession 4T 8'1 161' flay) The subtraction will be point by point and a new map developed therefrom.

The striking results of the technique thus far explained will be apparent by reference to the fractional map of FIG. 3 where the gravity contour lines for the corresponding area of FIG l have significantly different values, and more importantly, where the gravity anomalies are prominently displayed. Thus, for example, three positive gravity anomalies A, B and C appear. For anomaly A, the inner contour line has a gravity potential of +6, with successive contour lines decreasing to zero, and outwardly therefrom additional contour lines have negative values. Such contour lines do not appear on the map of F I6. I for the reason that the gravity potentials represented by the contour lines on FIG. 3 have, in the map ofFIG. I, been obscured by shallow and stronger gravity anomalies.

As will be later explained, the masses giving rise to the anomalies A, 8 and C, FIG. 3, are known to occur at depths between 12,000 feet and 24,000 feet. since the map of FIG. 3 resulted from the subtraction of the data from the averaging operator IGT l" l g 32 from the data obtained utilizing the averaging operator 0( v) For convenience, the depths which will give rise to corresponding anomalies on other maps resulting from the four operations with the four operators of FIG. 2 are as follows:

2T 0 to 3,000 g( ,y) am y) 2T 4T 3,000 to 6,000 00:, y) 00:, :1) 4T 8T 6,000 to 12,000 r r't May) 9( 0) 8T 16T 12,000 to 24,000 r\ 1n explaining the manner in which the foregoing operations are accomplished in analog computing equipment, several Figures will be utilized, each in part duplicating equipment of an earlier Figure. There will then be presented a block diagram illustrating the manner in which the number of components in the analog equipment may be decreased. The switching functions unduly complicate an understanding of the operations which may be more simply explained by using separate Figures of the kind just described. Finally, there will be presented techniques for a digital execution of the present invention.

Referring again to FIG. I, it will be observed that there has been marked thereon a line 20 representative of a traverse across the gravity map. on this line the small circles indicate gravity stations separated by the distances T at which values of gravity have been measured or established as by interpolation as explained above. If, now, the gravity potentials at each of the stations on the line 20 be plotted, a curve, such as that illustrated in FIG. 4 will be obtained, where the first gravity value will correspond with the station A,9 and the final value on the traverse line at Kl(,9.

As explained in the aforesaid application Ser. No. 2 l4,973 to Lawrence the interval T between stations is chosen to be less than one-half the length of the shortest fluctuation in the observed gravity potential, i.e., the distance between the beginning and end of the shortest anomaly as measured along the abscm. In one embodiment of the invention the distance T was selected as 3,000 feet. Though the averaging operators in accordance with the present invention are in terms of area, it is convenient to show these operators for the line or gravity profile 20 and they have been illustrated as 2T, 4T and 81 for profile 20. It is to be understood that there will be a plurality of profiles extending across the map of FIG. 1, each spaced vertically from the other preferably by distances equal to the spacing between the stations of profile 20, i.e., about 3,000 feet. To minimize the number of reference characters on FIG. I, only a few identifying characters have been utilized. Thus, for example, the first column A has thereon the row 9 identified. Thus, the first observing station for profile 20 is identified at the point A,9. Similarly, the station located at the center of the averaging areas may be identified as I,9. Finally, it will be noticed that the illustrated part of the map terminates at approximately the row VV. If all of the rows of the columns were to be labeled, they would appear in the same way as the rows and columns have been identified on the averaging operators of FIG. 2 except that they would be extended to cover the gravity map of FIG. 1. Accordingly, for every profile corresponding with the horizontal line through the rows 1, 2, 3, etc., there may be provided a gravity profile corresponding with the one illustrated in FIG. 4. These gravity profiles in turn may be represented by amplitude signals on a magnetic tape or alternatively by amplitude signals on any reproducible medium as, for example, variable area film, and by stored values in a digital system. The manner in which a record may be developed on magnetic tape is well understood by those skilled in the art, an optical arrangement for this purpose having been described in the aforesaid Lawrence application. Thus, referring to FIG. 5, it will be assumed that on a magnetic drum 30 there will have been recorded the gravity profiles beginning with the first profile taken along the first row I of FIG. I. There will be a pickup head l" associated with this record. Similarly, there will be additional pickup heads associated with each of the additional profiles, the pickup heads P P, and P being shown for the profiles respectively above and below row 9 identified on FIG. I. A motor 3] drives the drum 30 together with a tape drum 32 a third drum 33 as well as additional drums later to be described. These drums are preferably of like diameter and in each case the length of tape on the drum will be proportional to the distance on the map of FIG. 1 from initial boundary A to final boundary VV.

In order to develop each area averaging operator of FIG. 2 there will first be developed individual averages for each profile. The profiles will then be averaged together. Finally,

differences will be taken to provide the information for the new difference maps which can then be plotted on an areaaveraged basis.

Assuming now that the motor 3] has been energized to initiate rotation of the drums 30, 32 and 33 at the beginning of the record, it will be observed that pickup head P, will apply to an amplifier 34 signals representative of the gravity profile spaced just above the profile 20 on the map ofFlG. l. The output from the amplifier 34 is applied to an integrator 35 and, through a recording head 36, is recorded on the drum 32. This drum 32 has associated with it two pickup heath 37 and 38 spaced apart from a reference point 39 by distances equal to T corresponding with the separation distances between each ofthe stations illustrated in FIG. I and also in FIG. 2. The pickup head 37 has been indicated as being spaced from the reference point 39 by the value +T while the pickup head 38 is spaced from the reference point by the amount 'I, this being the correct notation with drum rotation as indicated by the arrow. The signal on drum 32 corresponding with f g(t)dr will be first applied to an amplifier 40 and thence through a resistor 41 to a summing amplifier 42. As the record arrives at the pickup head 38, signals representative of the gravity profile willbeapplied toan amplifier and thenoebywayof resistor 44 to the amplifier 42. It will be noted that the polarity of the inputs to amplifier 42 are of opposite sign; that from the amplifier 40 being negative and that from amplifier 43 positive. The opposing polarities are readily obtained by reversing the connections to one amplifier relative to those to the other and as applied to the summing resistors 41 and 44. The signal applies by way of summing resistor 41 may be represented as I g(l+T)dr and the signal applied by way of summing resistor maybe represented as /g(t7')dt. lnasmuchasit isdesiredto generate an output signal which is independent of the length of the operator, the output signal from the amplifier 42 is divided by the length of the operator, in the present case, 2T. Accordingly, the resistor 45 will have its tap or movable connection set at a value representative of l/2T). In this connection, the distance between the heads 37 and 38 corresponds with the value of 21. That distance will, of course, be proportional to twice the spacing of the observing stations appearing on the map on FIG. I. The output of the amplifier 42 alter the division just described is applied by way of a switch 47 to a recording head 48 associated with the drum 33. Thus, there will be recorded on drum 33 the profile detected by the pickup head P, after averaging by the operator 2T.

After the completion of the foregoing operations, the drum 30 will have been returned to its initial position. At this time, the switches 34a and 47, preferably ganged together, are moved to the next left-hand positions, i.e., to connect the pickup head P, to the amplifier 34 and to connect the output from the dividing resistor 45 to the next recording head 49. The second operation will be identical to that just described and as the drum 30 completes another revolution the switches 34a and 47 will again be stepped to the left until there will have been scanned the multiplicity of profiles recorded on the drum 30 and the avenge values of each over the interval 21 recorded on the drum 33.

Assuming now that there have been recorded on the drum 33 the averaged profiles with the averaging operator 21', it will be understood at once that the pickup heads P,', P. and P,.,' can reproduce continuously the averaged profiles. ll, now, these three averaged profiles are averaged together, then a consideration of area is introduced. More specifically, and referring to FIG. 2, there will have been recorded on the drum 33 the average values for a profile corresponding with the points H8, [8 and J8. Similarly, there will be corresponding averages for points on profiles 9 and at H, l and J. It, now, these profiles be averaged together, there will be obtained the average area-gravity potential l' l emu) across the map for the strip between H and J. The manner in which the average values as reproduced by pickup heads P., P. and P are utilized to accomplish the foregoing results will now be described in connection with FIG. 6 where the drums 30 and 33 have again been illustrated but with drum 32 omitted. in this Figure as well as in the arrangement of FIG. 5, the pickup heads associated with drum 33 are located in the same relau'onship in the record as are the pickup heads associated with drum 30. The reason for this will soon be made apparent. The pickup heads P.', P, and P,, are connected by a gang switch 50 respectively to summing resistors 51. 52 and 53 of a summing amplifier 54. Inasmuch as average values are desired, the resistor 55 has its associated contact or tap set at a value to divide the output of the amplifier 54 by three. In some instances, it may be desirable to record the average values obtained in the manner just described and an output terminal 57 connected to output conductor 58 may be provided for connection to a recorder of a kind later to be described, or it may be a recorder of the continuous type as illustrated in FIG 7 of said Lawrence application.

The average gravity values obtained at the output conductor 58 are applied by way of a summing resistor 59 to a summing amplifier 60. As indicated by the and signs, the polarities to this summing amplifier are reversed, the signal from summing resistor 59 being negative. The other input to summing amplifier 60 is obtained from pickup head P, of drum 30. Alter amplification by amplifier 34 the signal is applied through the summing resistor to the amplifier 60. Thus, there has been illustrated the manner in which there is obtained the operation inasmuch as there has already been described the manner in which the area averaging operator moves across the traverse of the map in discrete steps, there will now be explained how the system of FIG. 6 achieves readout of the desired information.

The output of amplifier 60 is applied to the input of amplifier 61 forming a part of a self-balancing measuring system and including a motor 62 operable in one direction or another proportional to the magnitude or phase of the output from amplifier 60. Such an arrangement of amplifier and motor is well understood by those skilled in the art and has been discussed in U.S. Pat. No. 2,l [3,164 to Williams. The motor 62, through its shaft 620, drives a plurality of print wheels 63 printing digits 0-9 and together forming a printer mechanism for applying to a chart 64 digits relative to the magiitude of the output of amplifier 60 and proportional to the quantity Counting mechanisms including print wheels are well known to those skilled in the art. The print wheels 63 are driven in succession one after the other by the shaft 62a and are suspended on a carriage 65 positioned along the chart by means of a violin string 66 suspended on pulleys, one of which is driven by a driving pulley 66a. The drive for pulley 66a comprises a pawl 67a and a ratchet wheel 67b. The pawl pivoted about the support 670 is operated by cam 67d driven through mechanical connection 67: and by motor 31. The cam 67d rotates the ratchet wheel 67!: one notch for each revolution of the drums 30 and 33. Thus, the ratchet wheel 67b moves the stepping switch 50 to the left through one position and at the same time moves the carriage 65 along the chart 64 by a distance proportional to the distance T.

It is to be observed that the print wheels 63 are illustrated in spaced relation with the chart 64. The chart 64 is held in this spaced relation by a mechanical linkage including the arm 68 which is pivoted at 68a. Arm 68 moves the chart into and out of engagement with the print wheels 63 in response to movement of arm 68b which is biased outwardly by spring 68c. Arm 68b is pivoted hitting arm 68d which carried a cam follower 68. The printing operation is directly controlled by a notched wheel 69 carrying a plurality of succeeding teeth and troughs, the tooth 69a and the trough 69b pulled as the motor 31 rotates drums 30 and 33 through a distance corresponding with the distance T, the wheel 69 is moved to bring the tooth 69a beneath the cam follower 68a. The mechanical linkages 68, 68b and 68d position the chart into engagement with the print wheels 63. When the wheel 69 rotates further so that the trough 69b is behind cam follower 68b, the chart is moved out of engagement with the print wheels. The chart 64 is likewise driven by way of the mechanical connection 67e. The chart 64 has been shown as endless and its length will be proportional, preferably equal, to the length of the gravity information stored on circumferential track of the drums 30 and 33.

For details of the print operating mechanism, only diagrammatically illustrated in FIG. 6, reference may be had to US. Pat. No. 2,080,065 to Ross et al. wherein instead of a print wheel, the carriage support and operating mechanism therefore have been illustrated as applied to a chart marker in the form of a pen. With the above understanding of the areas of the readout mechanism, a brief resume of the operation may be helpful. With the gravity records on drums 30 and 33 in their initial or zero positions in respect to the pickup heads it will be remembered that the chart 64 will likewise be in its initial position and the carriage 65 in its left-hand position. Accordingly, the print wheels 63 will print in succession with spacings therebetween equal to T the gravity values as determined at the output of amplifier 60 and as referred to in FIG. 1 across the first and uppermost row. The operation, of course, is continuous until there will have been recorded gravity values which may be held positive or negative as shown in FIG. 3 and of the same or differing magnitude. After a single revolution of drums 30 and 33 and of chart 64, the gang switch 50 is operated and the carriage 65 is stepped to row 02 of FIG. 1 and the operations are repeated, and it is in this manner that there is produced on the chart 64 the gravity values for each station. By merely interconnecting points of equal value the equal gravity lines may be drawn to delineate the gravity patterns as illustrated in FIG. 3.

It will now be seen that there has been provided an arrangement in which the operator has been moved from the left-hand side of the map, FIG. I, to

the right-hand side thereof and the manner in which the average values of gravity taken over the area represented by that operator have been read out and recorded as discrete values of gravity potential.

It will be understood that the foregoing operations are again carried out with a change in position of the operator by one unit T as from A,9 to A,l on the map of FIG. I. This is done by shifting the gang switch 50 one space to the left. By successive cycles of operation, corresponding with the multiplicity of traverses across the map, there will be generated a new set of gravity values by means of which there may be plotted a map corresponding to the foregoing function If gravity anomalies appear on the map, for example, the kind already described in connection with FIG. 3, it will be known that the masses giving rise to them will be at relatively shallow depth as, for example, from 0 to 3,000 feet. It will be understood, of course, thatthis range of depth. and those'earlier discussed are applicable to the examples utilized for explaining the invention. Different ranges will be associated with different intervals ofT.

What has been described thus far has been the steps involved in generating the function 2 T ly) my) As already stated, a map of this function provides useful information regarding anomalies falling in the depth range of 0 to 3,000 feet.

There will now be described the manner in which the funcis generated. By plotting values of this function on a map, useful information regarding anomalies falling in the depth range of 3,000 to 6,000 feet may be obtained. Referring to FIG. 7, the drums 30, 32 and 33 are again shown. It will be remembered that drum 33 has recorded thereon, in successive tracks, the gravity profiles along the rows l--l7, FIG. 1, averaged over the interval 2T. More particularly, the drum 33 has recorded on the track under the pickup head P the gravity profile along the row 8, FIG. I, averaged over the interval 2T; under the pickup head P, the gravity profile along the row 9 averaged over the interval 2T; and under the pickup head P the gravity profile along the row 10 averaged over the interval Also shown in FIG. 7 is the drum 70 which has recorded thereon, on successive tracks, gravity profiles recorded along the rows l-l7, FIG. 1, and averaged over the interval 4T, The manner in which the gravity profiles have been averaged over 4T is as follows.

The gravity profile along the row 8 has been recorded on drum 30 under the pickup head P,. This gravity profile signal is sensed by pickup head P amplified at 34, integrated at 35 and recorded on drum 32. This integrated gravity profile is picked up on drum 32 at the pickup head 71. The signal from pickup head 71 is amplified by amplifier 72 and connected through summing resistor 73 to an amplifier 74. The profile recorded on the drum 32 is also picked up by a pickup head 75 spaced by an interval 2T on the other side of the reference mark 39. It will be noted that the pickup heads 71 and 75 are spaced from one another by an interval 4T. The profile from pickup head 75 is amplifier by amplifier 76 and applied through summing resistor 77 to the amplifier 74. The signal from amplifier 76 is of opposite polarity to the signal from amplifier 72. As explained above, the output of amplifier 74 after division by four by the voltage divider 45 a will be proportional to the gravity profile along the row 8 averaged over the interval 4T. The output of amplifier 74 is connected through stepping switch 78 to the pickup head 79 which records the averaged gravity profile for the row 8, FIG. I, on a track of the drum 70. The gravity profile along the row 9 is next averaged over the interval 4T and recorded on the drum 70 as shown, the stepping switch 340 having been moved to the left to pick up the signal from pickup head P,. This signal is averaged over the interval 4T by means of the drum 32, summing amplifier 74 and voltage divider 45a, as described above. The stepping switch 78 is moved to the left one position so that the profile along the row 9 is recorded at the pickup head 80 on the drum 70. In a similar manner, the profile along the row It] averaged over the interval 4T is recorded by the recording head 81; the gravity profile along row 6 averaged over the interval 4T is recorded by recording head 82 and the profile along the row 7 averaged over the interval 4T is recorded by recording head 83.

The five recorded tracks referred to above are picked up by the recording heads 84-88. The five picked-up signals are connected through the stepping switch 89 and the summing resistors 9I95 to the input to summing amplifier 96. The output of summing amplifier 96 is connected to the voltage divider 97 which divides the output of amplifier 96 by a factor of 5. The signals appearing at the tap 98 are equal to the averaged values of the five gravity profiles recorded on the drum 70. The signal appearing at the tap 98 is the function Way) I This signal is applied through resistor 99 to one input of a summing amplifier I00. The signal proportional to other input to amplifier I00. The output of amplifier I is proportional to By moving stepping switches 34a, and 89 to successively different left-hand positions, the functions r'"| l l 00m!) way) will be generated in succession for each gravity profile. These functions can be plotted in a manner similar to that shown in FIG. 3 to produce a map which accentuates the anomalies falling in the depth range of 3,000 to 6,000 feet.

There has now been described in detail the manner in which the functions 2T 2 T 4 T are generated. There will now be described the manner in which the functions l l and l l I 90m!) 90 ,11) 00 ,11) 00 4/) are generated. FIG. 8 shows a complete analog computing system of the type required to generate all of the desired functions. To simplify the description, FIG. 8 is somewhat diagrammatic in that many of the amplifiers, stepping switches and averaging voltage dividers have been omitted. However, the inclusion and connection of these circuit components can readily be ascertained by comparing FIG. 7, showing all of these circuit components in detail, with that portion of FIG. 8 which repeats the showing of drums 30, 32, 33 and 70 but omits the detailed circuit components.

Gravity profiles averaged over the interval 81 are produced at the output of summing amplifier I01 and recorded on drum 102. Nine of these profiles are averaged in amplifier I03, the output of which is proportional to the function |-1 (m) a As before described, the function can be generated for all gravity profiles on the map shown in FIG. 1. This value is subtracted from the function Mm) in the amplifier I04 to produce the function 00ml) 9 (m) This function can be plotted to form a map which accentuates anomalies falling in the depth range of 6,000 to 12,000 feet.

In order to generate the function any) Way) the drum I05 is provided. The signals proportional to gravity profiles averaged over the interval I6T are obtained from summing amplifier 106. These gravity profiles are recorded on the drum I05. Seventeen of the profiles recorded on drum I05 are picked up simultaneously and averaged in the amplifier 107. The output of this amplifier, proportional to |--1 9 ,11) is applied to amplifier I08. The function l 0 (w) is subtracted from the function r 005.11) by the amplifier 108. The function ml) slay) can be obtained for all of the gravity profiles on the map shown in FIG. 1. The functions r 1 r-1 was) 90 .11) for the map of FIG. I are plotted in FIG. 3. The map of FIG. 3 accentuates the anomalies falling in the depth range of 12,000 to 24,000 feet.

There has been described the manner in which a gravity map of the type shown in FIG. I has been transformed to a map of the type shown in FIG. 3 by analog techniques.

There will now be described the manner in which the gravitational data is treated digitally on an area basis to produce a map such as shown in FIG. 3. In FIG. 9 there is shown a diagrammatic representation of a data processing system. This is a representation of most commonly available digital data processing systems which include an input-output units for accepting input data 121 and for producing as an output reports indicated at 122. The digital data processing system operates under control of instructions 123 which are fed into the computer through input-output units I20. External data 121 and instructions 123 are stored in the computer internal storage unit 124. These data and instructions are processed by arithmetic unit 125 under control of the control unit 126 which operates in accordance with instructions 123.

There will now be described a particular digital computer which can be used in digitally processing the gravitational data. However, it will be understood that the input-output units 120, internal storage unit I24, arithmetic unit 125 and control unit 126 can take many forms apart from those to be subsequently described.

In the computing system to be presently described, data I21 and instructions 123 are punched onto cards such as those shown in FIG. I0. These cards are prepared by an operator at a card punch. The operator prepares a card similar to the ones shown in FIG. 10 for each of the gravitational profiles on the map of FIG. I. As an example, the card 127 will be punched to represent the gravitational values along row 9 of FIG. 1. Each of the vertical columns on the card is a digital code representing the gravitational potential at a particular station along row 9. For example, the vertical column 128 contains a punched digital code representing the observed gravity at the station A,9, FIG. 1. Vertical column I29 contains a punched digital code representing the observed gravity at the station B3 and so on. The observed gravity values for each of the rows I-17 are punched onto cards similar to those shown in FIG. I0. Cards containing the gravitational information are stacked in the card reader 130, FIG. 11. Any commercial available card readers may be used for this purpose, the card reader commercially available as IBM Model No. 522 is one of many suitable for this purpose. As the cards are read, the codes are translated in the translator I31 to a code which is usable by the computer. Translator l3! converts each card code to a code which is usable in the magnetic drum computing system shown in FIG. II. The commercially available IBM 650 Magnetic Drum Computer is suitable for use as the computer illustrated in FIG. II.

Before describing the manner in which the computing system shown in FIG. II operates on the gravitational data to produceamapsuchasshowninFlG.3,therewillbe described several operational features of the computing system. An understanding of the operation of the computer in executing the following stored instructions is necessary to understand the techniques used to prooem the gravitational data:

L'I'heinstruction IICI OOOusedtonarnferdatafromthe cardreadertothestoragelocatimoraddremesininternal storage of the computer;

2. Theinstmction ADDOOOandsimilar inatructionsusedto perform arithmetical operation on data stored in internal storage;

3. 'IhelnatructionsSlS000,ClS 008,.IMP06I and otherinstructiona used in performing at indexing cycle;

4. The instructions PNI OOOandCSP 001 used in printing out the computed gravitational values.

The performance of the foregoing imtructiom described in conjunction with the following short description of the data processing system shown in FIG. I I.

The codes from translator 13] are stored in one of the storage locations on magnetic dnrrn I32 in response to, for example, the instruction RC! 001 This instruction haanoperation code portion (Op. Code) RC1 specifying that the next cardincardreader IBBistoberead ndanaddrQportion, 00l,specifyingthatcodesfromthecardaretobestoredin consecutive storage locations on magnetic drum I32 beginning at storage location OOI.

Magnetic drum I32 includes a plurality of quick access bands, the quick access bands I ,2 It] being shown and a plurality of main storage bands, the main storage bands I, 2, 3 being shown. The input codes are stored in particular storage locations on the magnetic drum I32 under control of the head switching control circuit I33. Head switching circuit I33 'a, in turn, responsive to the address portion ofthe instruction stored in address register I340.

Each band on magnetic drum 132 is divided into many unit areas per inch, each of which stores a bit. A magnetized area represents a i; an unmagnetiaed area represenu a 0. Each code from translator I31 can be put into one bit position on a hand We will assume that all of the codes on a card can be recorded on one band. Each band on magnetic drum 132 will be assumed to contain 80 storage locations. Therefore, main storage band I contains the storage locations l-80, main storage band 2 contains the storage locations 8l--l60, main storage band 3 contains the storage locations l6l240, and

so on.

The codes are transferred to and from storage locations on magnetic drum 132 under control of the control unit 134. The control unit I34 includes an instruction register 135 which stores an instruction to be executed. Each instruction to be executed includes an address portion and an operation portion. The address portion of the instruction is set into the address register 134a as previously mentioned. This address register [340 controls the storage location on magnetic drum 132 from which the code to be operated on is transferred.

The operation portion of the instruction register 135 is decoded by decoder I36 which controls many functions including the operation to be performed by arithmetic unit 137. When the operation has been performed by arithmetic unit I37, the arithmetic unit I37 advances the instruction counter I38 by one count to indicate the present instruction has been performed and that the next instruction can be called up from memory to be performed.

The operation of the control unit I34 and the arithmetic unit I37 rs best illustrated by describing the operation in conjunction with the performance of a simple instruction. As an example, the instruction ADD 268 that is stored in storage focation 062 will be performed. This instruction means that the contents of storage location 268 are to be added to the contents of the accumulator I39 in the arithmetic unit. The operating cycle can best be described as consisting of seven steps. The seven steps are listed below and the associated numbers are indicated on the drawing as circled numbers on the data flow and control lines which perform the step. The steps in the performance of the instruction ADD 268 are as follows:

1. Transfer the operation part of the instruction, ADD, from the instruction register to the decoder I36.

2. Transfer the address part of the instruction, 268, from the instruction register 135 to the addres register I340.

3. Copy into the arithmetic unit 137 the operand (which may be either data or an instruction) located at address 268.

4. Execute the required operation, ADD, in the arithmetic unit. Notify the control unit when the operation is executed.

5. Increase the number 062 in the instruction counter I38 by l, to 063, to indicate the address ofthe next instruction.

6. Transfer the number 063 from the instruction counter I38 to the address register 1340.

7. Get the instruction, SUB 495, located at address 063 and put it into the instruction register.

In order to make the most efficient use of programming time and the use of storage for instructions, and indexing cycle is provided for in the digital computing system. An index register I40 together with comparator I41 are used to change a singleinatructionsothatitcanbeusedoverandover againto carry out a program of instructions. The operation of the index register I40 and comparator I41 in performing an indexing cycle is best illustrated by the following example. Assume that it is desired to add together the contents of three storage locations 068, 069 and 070 and to store the result in storage location 07L The easy way to perform this operation would be to insert the following instructions in sequence in the program assuming that the program is starting with the instruction stored in location 0.60:

Instructions Address Op. Code Address 060 ADD 068 06l ADD 069 062 ADD 070 063 S'I'A 07! In carrying out this simple program, the computer would remove the instruction ADD 068 from storage location 060 and insert it in instruction register I35. The instruction would be performed by adding the contents of storage location 068 to the accumulator 139. After performance of this instruction the instruction stored in storage location 061 would be put into instruction register I35 and this instruction would be perfonned by adding the contents of 069 to accumulator I39. After performance of this instruction, the instruction stored in location 062 would be transferred to instruction register 135 and this instruction executed by adding the contents of storage location 070 to the accumulator 139. Next, the instruction stored in storage location 063 is transferred to instruction re gister I35 and this instruction is performed by transferring the contents of the accumulator to the storage location 07 l While the above routine is quite straightforward when only the contents of three storage locations are to be added together, this approach becomes quite cumbersome when a great number of storage locations are to be added together. In order to perform this operation more simply an indexing cycle is programmed. The above problem would be programmed with an indexing cycle as follows:

Storage Location 7 Assuming that we begin the program With the instruction stored at storage location 060, the instruction $18 000 is per formed by the decoder 136 acting over control line I42 to set the index register I40 to zero. The next instruction, ADD 068 is performed by address register I340 acting over the control line I43 to gate the contents of storage location 068 over the data flow line 144 to the arithmetic unit. The decoder I36 acts through control litre 145 to cause the number in storage location 068 to be added to the contents of accumulator 139.

m lnstructlms location Op code Addrea Mn 8l8 (I!) Set index register to 0.

06] ADD 068 Add tosccmnulator the number stored at the address 068 plus contents the index register 0152 INC nor Increment index register by I.

063.. ClS nos Cmnpare contents or Index register with the contents or storage location 008 which contains the number 3. Ir contents are uneapnl, take the next instruction in pence 064; it equal, skip one Instruction to the storage location 065.

g Jump to e instruction at storage location Stare contents otwcumulstor in storage location 071.

The nextinllructionINCOOl isperforrnedbythedecoder I36 acting over control line 142 to 'mcremem index reg'lter I40 by I.

The nextinstructlonclsoollisperlonnedbythecompcator 141 which compares the content ofindex reg'srer I40, the contentsnowbeingmLwiththecontentsofstoraplo-catim 008 ThestorngelocationOOScontainsthenumberlSince the comparator 141 indicates that the two numbers are unequal, it acts over control line I46 to gate the next instruction stored in storage location 064 to the instruction register.

Theinstructionstoredinltoragelocationoflisajrmpinstruction JMP on. The instruction JMP 061 acts through control line I43 to cause the headswitching control circuitry I33 to transfer the instruction stored at storage locttion 061 to the instruction register. Th'u differs from the normal sequence of operation in which the instruction at address 065 would next be transferred to imtruotion register 135.

The instruction stored at storage locations 061 is ADD 068. The contents of the index register 140 are added to the address. portion 068. The index register [40 now contains a I ri when this is added to the address 068, the addres is modified to 069. The contents of storage location 069 are added to the contents of accumulator I39 to complete this instruction.

The instructions INC 00] and CIS 008 are performed as before Since the contents of index register 140 is incremented t0 2 and since this still produces no comparison with the contents of storage location 008, a 3, the next instruction IMP 06l is performed. This causes a jump back into the instruction stored at address 061 and another cycle is performed. In this cycle the contents of storage location 070 are added to the accumulator. In this cycle, when the instruction CIS 008 is performed. the comparator 14! indicates a comparison. The

comparator I41 then acts over control line 146 to skip an instrucuon and to gate the instruction stored at storage location 065 to the instruction register I35. The motion stored at address 065 is STA 07 l. Th: instruction is performed by stormg the contents ofthe accumulator in storage location 07 I.

In this manner, the contents of storage locations 068, 069 and 070 have been added together and the results stored at location 071. This sequence has been performed by using indexing cycles.

The remaining component in the digital computer of FIG. II to be described is the output printer indicated generally at 1Mv Digital codes from storage are connected switching control 133 over the data line 161 to the amplifier l6ls. The digital codes are decoded by positioning mechanism I62 which rotates the shaft I62: to set the print wheels lfltotheproperpoeitioncorrespondingwiththe digital code to be printed. The manner in which digital codes are translated to rotational movement to position printing wheels is well known to those skilled in the art.

The print wheels 163 are positioned to be brought into ongagement with the moving chart I64. The moving chart I is brought into engagement with the print wheek I63 by means of the print control motor I70. In response to an instruction PNl which is decoded in decoder I36, the print control motor ['70 will be energized and will rotate an incremental amount. The print control motor I70 rotates the notched wheel I71 to cause the tooth 172 to engage cam follower 173 on mechanical linkage I74. When a tooth of notched wheel 17] engages the cam follower I73, the mechanical linkage is rocked forward causingtheann I75topushthemovingrecord lflimo engagement with the print wheels 163. Further rotation of the wheel 17] causes cam follower I73 to fall into a trough in the head i hecl thereby disengaging the chart 164 from print wheels I63.

Actuation of print motor I70 also rotates the moving chart I64 by means of the mechanical connection at 176. Afier the printing of the digit has been completed, the chart 164 is incremented to the next position at which the printing m to occur. The operation of the printer is best described in conjunction with the performance of an instruction. Assume the instruction PN1 068 is in the instruction register I35 The address portion, 068, is transferred to address register 1340. Addrgs register 134a acts over control line 143 to set the head switching control I33 so that the contents of storage location 068 are transferred over line 16I, through amplifier 1610 to the decoder 162. The decoder 162 sets the print wheels 163 to tin number specified by the contents of storage location 068. The 0p. Code portion PNI of the instruction is decoded in decoder 136. In response to the instruction PNl the decoder 136 acts over control line 1700 to actuate print control motor 170. Print control motor I70 rotates the notched wheel 17] to cause the record 164 to be moved into engagement with print wheels I63 to print the number recorded in storage location 068. Further rotation of notched wheel 171 causes the record 164 to be moved out of engagement with the print wheels I63. Still further rotation of mechanical linkage 171a causes the moving record to be moved at 176 thereby incrementing the record to the next position which is to be printed. in making the gravitational computations involved in the present inven tion. the moving record will be incremented a distance corresponding to the distance T on the moving record.

The printer I60 also has provision to move the print wheels 163 to different columns on the moving chart. The print wheels are carried on a carriage I65 which is movable along the shaft 169 by means of the violin string 166 which is moved at one end by the pulley I660. The pulley 166a is rotated by ratchet wheel 16'! which is held in position by the associated pawl 167a. The ratchet wheel l67b is rotated in response to the column control motor [77 Column control motor [77 is actuated in response to an instruction CSP. The instruction CS! is decoded in decoder 136 which acts over control line 178 to actuate column control motor 177.

When a complete column including all of the values across a gravitational profile has been printed out, an instruction CSP will be programmed to increment the print head to the next column so that another gravitational profile can be printed on {the moving record I64. In the computations involved in the present invention, the print wheel will be incremented by a columnar distance corresponding to the distance T.

There will now be described the manner in which the digital computing system shown in FIG. ll operates on the gravitational data in accordance with this invention. There will be described the manner in which the gravitational data along the profiles 8, 9 and 10, FIG. 1, are combined on an area basis to form the function 2 T r--n al ulaw, y) This expression will be computed for the profile along the row 9, FIG. I.

As previously mentioned, the gravitational data along rows 8, 9and 10, FIG. I, are punched into three cards. It will be assumed that the card containing the gravitational data along the row8 is the next card in the card reader 130, FIG. ll. lt will also he assumed that the printer wheels I63 are now positioned over a column on record 164 which will correspond with row 9 on the final record. The computer will then proceed with the following program beginning with the in- The instruction SIS 000 sets the index register to 0. The instruction CM I00 clears accumulator I39 and adds to the accumulator the number stored at the address 100 which is the gravitational value at the first station along the row 8. The instructi ons ADD lOl and ADD I02 completes the sum of all gravitational valuesin E interval 21, i .e .,fgii+ 'i')drjjg( t-T) Storage location ml... Constant used in computatbn. lIIL Do.

llllL.

010 Road the next card in Card Reader 01L Read the ncxtcard in Card Reader 013 Read the next card in C 3: Set Index Register to D.

egistcr. Add to the accumulator the number s Add to the accumulator the number stored I1 and store in 100 consecutive locations beginning at address 100. I1 and store in 100 consecutive locations beginning at address 1X). srd Reader #1 and store in It!) consecutive locations beginning at address 300. Cigar the accumulator and add to the eccumuJntor the number stored at the address I00 plus the contents oi the Index torad at the address l plus the contents of the Index Register.

at the addrms 102 plus the contents of the Index Register.

Dll'- Div ide the contmts oi the accumulator b the number stored at address ml.

018. 400 Store the canton of the accumulator at sddru 400 plus the contents of the Index Register.

019... INC 001 Incremmt the Index R tar by 1.

1m. CIB 002 Compare the contents the Index Reglsur with the number stored in location 002 which contains the number 48.

If the contents are unequal, take the next instruction; if equal, ship 1 instruction.

1MP 014 Arrival at this point rum the receding com rlson means that the cycle count is not yet complete; therefore, jump o storage location 014 to another try m. SIS (I!) 021.. ADD 201 026. w ADD m can. DIA (Ill 02L STA am 028 INC m1 0D CIS one 9m 'lhse instructions are the some as instructions 013-02), except that the blocks of data from the next two cards are being averaged over the interval 21.

032. CAL 3t!) 0%. ADD am ADD U2 IE6. DIA till 0%" STA CD 037 IN C on 089 IMP 032 Oil) SIS (Ill Set Index Register to 0.

041 (AA 400 Clam- 21B accumulator and add to the accumulator the number stored at the address 4001mm the contents of the Index cg ter.

042. ADD 500 Add to the accumulator the number storg at the address sou plus the contents of the Index Register.

043 ADD 600 Add to the accumulator the number stor at the address 600 plus the contents 0! the Index Register.

0 PIA 001 Divide the contents of the accumuhttor by the umber stored at address 003.

M5 sTA 700 Store the contents oi the accumulator at the ad 7w plus the mutants oi the Index Register.

046. INC 001 Increment the Index R tar by l.

47. C18 002 Compare the contents 0 the Index Register with the number stored in location 002 which contains the number 48.

It the contents are unequal, take the next instruction; if equal, skip l instruction.

M8 J MP 04! Arrival at this point from the preceding com rlson means that the cycle count is not yet complete; therefore, jump to storage location 038 to beg n another cycfi D19. BIS (Ill Set Index Register to 0.

" 0AA 201 Cldear gm acgrrmuhtor and add to the accumulator the number stored at the address 201 plus the contents oi the In- 05L BUA 70o Subtract mm the accumulator the number stored at the address 700 plus the contents of the Index Register.

062. STA son Store the contents or the accumulator at the address 800 plus the contents of the Index Register.

053.. INC 001 Increment the Index R tar by l.

54.. (I5 002 Com re the contents the Index Registerwith the number stored in location 002 which contains the number 48.

It t e contents are unequal, take the next instruction; if equal, skip l instruction.

065. J MP 050 Arrival at this point from the receding comparison means that the cycle count is not yet complete; therefore, jump to storage location 050 to b n another eye a.

050.. SIS (I!) Set Index R ister to 0.

057. PM! 800 Print on the rinter #1 the number stored at the address 800 plus the contents of the Index Register.

058. INC (Ill Increment the Index It later by 1.

CIB 002 Compare the contents 0 the Index Register with the number stored in location 002 which contains the number 48.

I! the contents are unequal, talre the next instruction; 1! equal, skip 1 instruction.

000.. I MP 0157 Arrival at this point from the receding com 11 means that the cycle count is not yet complete; therefore, jump to storage location 057 to n another eye e.

CB? 001 Increment the printing head y 1 column. 7 H V H V a m The 3r ln performfii tlse It: The instruction DIA 001 causes the surn stored in the E above propels is as fdlowa The instruction RCI 100 u cumulatzor I39 to be divided by 3 which is the contents of decoded in degrades ISQ acts ovengoutrol line 11932 storage location 001. By dividing the contents of the accumu' card 'F read out the 8" p lstor by 3, the gravitational value averaged over an interval 2T in; the gravity values along the profile of row 8, FIG. 1. The i nbmi i addressportionct'thisinstructiomdeoodedinaddressregisser I cu vet control a w p he I w lat'glhitrmcgrusrrt 400stores the contents ofthe accumuconseeutive storage locations on magnetic drum 132. The V codes will be stored in locations 100 to 149 since there are 49 The ndex register is incr men ed by the instruction INC codes representing the gravitational values at each of the sta- 001', and a comparison is made which indicates the indexing tions A,8 to VVJ on FIG. 1. Similarly, the next two insrmccycle is not complete. Therefore, the cycle is started over lions RC1 200 and RCI 300 will cause the digital codes beginning at the instruction CM 100 beginning at address representing gravitational values along the rows 9 and 10, 014. However. during this cycle each of the addresses will be FIG. I, to be stored in consecutive storage locations beginning incremented by the contents of the index register which is l.

at eddre. 200 and address 300 respectively. In order to Therefore, the gravitational values stored at storage locations generate an averaged gravity profile over the smoothing interval 31, the irltructions at adthesses 0l3 through 021 are executed.

ml, 102 and 103 will be added and divided by 3 and these will be stored in storage location 401. in the next indexing cycle the s tents ot' storag e locations I02, I03 and 104 will be added. divided by 3 and stored in storage locations 402. The indexing cycles will continue until all 49 ot the gravitational values along the row 8 of FIG. I have been averaged over the interval 2T. At this time the index register will contain a 49 and an equal comparison will cause the computer to skip to the instruction at address 022 which is SIS 000.

The same cycles described above will be repeated for the gravitational values on the rows 9 and 10. These gravitational values will be averaged over the interval 21' as described above. In order to generate area-gravity profiles by combining a plurality of the profiles averaged by the same smoothing interval, the instructions at addresses 040 through 048 are executed.

The block of instnictions stored at addresses 040 through 048 causes the three gravity profiles from the rows 8, 9 and 10. which have been avenged over the interval 2T, to be added together and divided by 3 to produce the average area profile represented as 2 T :-rmay) The averaged area profile are called up from storage and subtracted from the values 35 g(.r,y) which have previously been stored in consecutive storage locations starting at address 200. This subtraction is perfonned by the instructions at the addresses 049 through 055.

The results of this subtraction, representing the expression l' "l g(= yJ- M 2/) are stored in consecutive storage locations starting at address 800.

The values of 2 T 4" l m 10- m. y)

are printed out on a column of the moving chart by the instructions at the addresses 056060.

Finally, the instruction CS? 001 increments the printing head to the right by 1 column so that during the next cycle of operation the values 2 T will be printed in an adjacent column When the gravitational data from all of the stations on the map of FIG. I have been averaged on an area basis and printed on the record 164, equal values on the chart can be interconnected to form an equigravity map such as that shown in FIG. 3.

Referring now to the flow sheet shown in FIG. la the gravity profile g(y,) which may be, for example, the gravity values along the line 20 in FIG. 1, is averaged over the smoothing interval IT as indicated at 201. Similarly, the gravity profiles g(y,) and g(y,), which may be a series of gravity values along lines parallel to and below the line 20 in FIG. I, are averaged over the same smoothing interval 21' as indicated at 202 and 203. The smoothed gravity profiles g(.r,y),. g(.r,y and g(x,y) are averaged as indicated at 204 to generate the average area value 2 T In order to accentuate the appearance of anomalies at a particular depth, the area gravity value is subtracted from the value g(.r,y as indicated at 205.

5 To accentuate anomalies at a different depth, the area gravity value 4T l' "'i 0( y) I0 is subtracted from the area gravity value as indicated at 206. The area gravity value 15 4T l' "l m. u)

is generated by averaging gravity profiles over the interval 41' as indicated at 207-209 and then averaging the smoothed profiles on an area basis as indicated at 210.

The foregoing demonstrates the principles of the digital computer routine which may be extended to include generating values which accentuate anomalies at differing depths as previously discussed.

Of course, it will be understood that various modifications may be made without departing from the principles of the invention. The appended claims are, therefore, intended to cover any such modifications within the true spirit and scope of the invention.

l. eTnethod for processing data representing physical properties of the earth including anomalies in a particular area comprising the following sequential steps executed by an automatic computin apparatus:

generating signals representing smoothing data profiles 3088 lines of said particular area, said smoothed profiles being smoothed by differing Smoothing intervals extending along said data profiles.

generating signals representing area-data values comprising the combination of a plurality of the profiles smoothed by the same smoothing intervals, and

generating signals representing subtracting an area-data value formed by combined profiles smoothed by one smoothing interval from an area-data value formed by combined profiles smoothed by a different smoothing interval to enhance the appearance of the anomalies on an area basis.

2. The method of claim 1 in which the step of generating signals representing said smoothed profiles comprises integrating with respect to distance along said data profiles,

and

algebraically adding together values from said integrated profile corresponding with f g,( r+n T)dt f g,( tn T)dr where 3,") represents data values along the x data profile where 07 represents one-half the smoothing interval, and

t represents distance along said data profile to provide a resultant sum.

3. The method of operating a computing apparatus to treat gravity profiles representing gravitational anomalies comprising the following sequential steps executed by an automatic computing apparatus:

generating a plurality of transducible digital codes representing smoothing gravity profiles g(x,y) over differing smoothing intervals extending along each gravity profile,

generating transducible digital codes representing gravity profiles smoothed by the same smoothing interval and representing a plurality of averaged area-gravity values, and

generating transducible digital codes representing subtracting averaged area values one from the other to generate difference area-gravity values thereby to enhance the appearance of anomalies on the separate several difference area-gravity values.

Claims (14)

1. The method for processing data representing physical properties of the earth including anomalies in a particular area comprising the following sequential steps executed by an automatic computing apparatus: generating signals representing smoothing data profiles across lines of said particular area, said smoothed profiles being smoothed by differing smoothing intervals extending along said data profiles, generating signals representing area-data values comprising the combination of a plurality of the profiles smoothed by the same smoothing intervals, and generating signals representing subtracting an area-data value formed by combined profiles smoothed by one smoothing interval from an area-data value formed by combined profiles smoothed by a different smoothing interval to enhance the appearance of the anomalies on an area basis.

2. The method of claim 1 in which the step of generating signals representing said smoothed profiles comprises integrating with respect to distance along said data profiles, and algebraically adding together values from said integrated profile corresponding with gx(t+nT)dt- gx(t-nT)dt where gx(t) represents data values along the x data profile where nT represents one-half the smoothing interval, and t represents distance along said data profile to provide a resultant sum.

3. The method of operating a computing apparatus to treat gravity profiles representing gravitational anomalies comprising the following sequential steps executed by an automatic computing apparatus: generating a plurality of transducible digital codes representing smoothing gravity profiles g(x,y) over differing smoothing intervals extending along each gravity profile, generating transducible digital codes representing gravity profiles smoothed by the same smoothing interval and representing a plurality of averaged area-gravity values, and generating transducible digital codes representing subtracting averaged area values one from the other to generate difference area-gravity values thereby to enhance the appearance of anomalies on the separate several difference area-gravity values.

4. The method of operating a computing apparatus recited in claim 3 in which said step of generating transducible digital codes representing averaged area-gravity values comprises averaging a group of gravity profiles each of which is smoothed by the interval 2T, averaging A group of profiles each of which is smoothed by the interval 4T and by further averaging other groups of smoothed gravity profiles, the profiles in each group each being smoothed by smoothing intervals represented by 2nT where n is an integer and T is one-half the length of the smallest smoothing interval.

5. The method of operating a computing apparatus recited in claim 4 wherein said step of generating transducible digital codes representing averaged area-gravity values comprises averaging 2n+1 of said profiles smoothed over the smoothing interval 2nT to form the averaged area-gravity value and averaging 2n 1+1 of said profiles smoothed over the interval 2n 1T to form the averaged area-gravity value and said step of generating transducible digital codes representing subtracting averaged area values comprises subtracting the averaged area-gravity value from the averaged area-gravity value to generate a plurality of difference values which enhance the appearance of the anomalies in a given depth range.

6. The method of operating a computing apparatus recited in claim 4 wherein said step of generating transducible digital codes representing area-gravity values comprises averaging three of said profiles smoothed over the smoothing interval 2T to form the averaged area value and wherein said step of generating transducible digital codes representing subtracting averaged area values comprises subtracting the averaged area-gravity value from the gravity profile g(x,y) to compute a difference value on an area basis which enhances the appearance of anomalies in one given depth range, wherein said step of generating transducible digital codes representing averaged area-gravity values comprises averaging five of said profiles smoothed over the smoothing interval 4T averaged to form the averaged area-gravity value and wherein said step of generating transducible digital codes representing subtracting averaged area values comprises subtracting the averaged area-gravity value from the averaged area-gravity value to obtain a difference value on an area basis which enhances the appearance of anomalies in a second given depth range, and wherein further difference values are obtained to enhance anomalies appearing in other depth ranges by repeating said step of generating transducible digital codes representing averaged area-gravity values combining 2n+ 1 of said profiles smoothed over the smoothing interval 2nT to form the averaged area-gravity value and combining 2n 1+1 of said profiles smoothed over the interval 2(n-1)T to form the averaged area-gravity value and by repeating said step of generating transducible digital codes representing subtracting the averaged area-gravity value from the averaged area-gravity value to obtain said difference values which enhance the appearance of the anomalies in given ranges of depth.

7. The machine implemented method for automatically treating data representing a plurality of gravity profiles separated one from the other by a distance T and together coextensive with a mapped area which comprises generating signals in said machine representing modified gravity profiles in response to signals in said machine representing gravity values from each profile separated by the distance T wherein the generating step includes generating signals representing algebraic addition together of said values in accordance with the expression gx(t+T)dt- gx(t-T)dt where gx(t) represents gravity values along the x gravity profile, T represents one-half the distance of the smallest smoothing operator, and t represents distance along said gravity profile to produce physical representations in said machine representing a resultant sum, modifying said sum by the factor (1/2T) further modified by division by the number of profiles which have been added together, generating signals in said machine representing subtracting said modified profiles averaged together with one smoothing interval from other modified gravity profiles including a different smoothing interval, and generating signals in said machine representing said gravity values each separated from the other by the distance t for production of new gravity values in the same locations on the mapped area.

8. The method of operating a programmed computing apparatus to treat gravity information representing gravitational anomalies in a particular area which comprises generating signals in said computing apparatus representing a plurality of gravity profiles derived from said gravity information each of which represents said gravity information across a different section of said area, generating signals in said computing apparatus representing smoothing each of said gravity profiles by differing smoothing intervals extending along said gravity profiles, generating signals in said computing apparatus representing averaging together groups of said smoothed gravity profiles, the gravity profiles in each group having been smoothed by the same smoothing interval, to obtain averaged area-gravity values, and generating signals in said computing apparatus representing subtracting said averaged area values one from the other to generate difference area-gravity values thereby to enhance the appearance of anomalies on the separate several difference area-gravity values.

9. The method of automatically operating a computing apparatus to treat gravity information to obtain an averaged area-gravity value relative to a particular location x,y so that gravitational anomalies represented by said information are enhanced comprising the steps of, generating signals within said computing apparatus representing gravity profiles of said gravity information across a particular section, each of said gravity profiles representing gravity information along parallel lines spaced integral multiples of an interval distance T from the location x,y for which the averaged area-gravity value is to be obtained, generating signals within said computing apparatus representing smoothing each of said gravity profiles to form a plurality of smoothed gravity profiles, smoothed by differing smoothing intervals extending along said profiles, generating signals within said computing apparatus averaging together a group of smoothed gravity profiles each of which has been smoothed by a smoothing interval which is an even multiple of the distance T to represent a plurality of averaged area-gravity values, an equal number of profiles in each group being spaced on both sides of the location x,y by integral multiples of said distance T with the furthermost spaced profile in each group being spaced a distance from said location x,y corresponding with one-half the smoothing interval used to smooth said profiles, and generating signals within said computing apparatus representing subtracting said averaged area values one from the other to represent difference area-gravity values thereby to enhance the appearance of anomalies on the separate several difference area-gravity values.

10. The method recited in claim 9 wherein said step of generating signals within said computing apparatus representing smoothed gravity profiles comprises representing integrating said gravity profiles with respect to distance, and algebraically obtaining the difference between an integrated gravity profile represenTed by the gx(t+nT)dt and gx(t-nT)dt where gx(t) represents gravity values along the x gravity profile, t represents distance along said gravity profile and n is an integer.

11. The method recited in claim 9 wherein said step of generating signals within said computing apparatus representing said plurality of averaged gravity profiles comprises averaging together the smoothed gravity profile passing through the location x,y and an equal number of smoothed gravity profiles on both sides of location x,y the total number of smoothed gravity profiles which are averaged being specified by 2n+1, and wherein each of the smoothed gravity profiles has been smoothed by an interval 2nT where n is an integer.

12. The method recited in claim 11 wherein said step of generating signals within said computing apparatus represents subtracting said area-gravity values comprises subtracting an area-gravity value formed by averaging gravity profiles smoothed by the integral 2nT from an area-gravity value formed by averaging gravity profiles smoothed by the interval 2(n-1)T to form a difference area-gravity value which accentuates anomalies in a particular depth range.

13. The computer performed method of automatically and sequentially processing data representing physical properties of the earth including anomalies in a particular area which comprises converting said data to first physical representations within said computer representing data profiles across lines of said area, generating second physical representations within said computer from said first physical representation representing smoothing each of said profiles by differing smoothing intervals extending along said profiles, generating third physical representations within said computer from said second physical representation representing adding a plurality of profiles smoothed by the same sampling interval to represent a first sum, generating fourth physical representations within said computer from said first and second physical representations representing adding a plurality of profiles smoothed by a different smoothing interval to represent a second sum, and generating fifth physical representations within said computer from said third and fourth physical representations representing subtracting said first sum from said second sum to enhance the appearance of an anomaly representing said physical properties of the earth.

14. Apparatus for processing gravity profile data representing gravitational anomalies of the earth in a particular area which have been converted to physical representations representing gravitational values including circuitry comprising an averaging means for generating from said gravity profile data first signals representing gravity profiles smoothed by differing smoothing intervals extending along said profiles, an adder means for generating second signals from said first signals representing adding together a plurality of said gravity profiles smoothed by a first smoothing interval to generate a first sum, an adder means for generating third signals from said first signals representing adding together a plurality of said gravity profiles smoothed by a second smoothing interval, which is different from said first smoothing interval, to generate a second sum, and a difference means for generating fourth signals from said second signals and said third signals representing subtracting said first sum from said second sum to enhance the appearance of anomalies in the resultant.

Images