C                                                                       00000030
C                                                                       00000040
C          POINT                                                        00000050
C                                                                       00000060
C      TO ABSTRACT POINT FREE AIR ANOMALIES FOR A PARTICULAR AREA FROM  00000070
C        A TAPE FILE, ESTIMATE THEIR ACCURACIES AND WRITE ON DISC.      00000080
C                                                                       00000090
C      C. L. MERRY   ---   JULY, 1974                                   00000100
C                                                                       00000110
C      ACCURACY ESTIMATES ARE MADE ACCORDING TO: MERRY AND VANICEK      00000120
C      (1974) A METHOD FOR ASTROGRAVIMETRIC GEOID COMPUTATION, TECH. REP00000130
C      # 27, DEPT. OF SURV. ENGG., UND.                                 00000140
C                                                                       00000150
C                                                                       00000160
C      INPUT DATA                                                       00000170
C                                                                       00000180
C      CARD:                                                            00000190
C          LIMITS OF AREA INTEREST: LOWER AND UPPER LATITUDES, LOWER    00000200
C      AND UPPER LONGITUDES (ALL IN DEGREES) - 4F8.2 (LONG. POSITIVE WES00000210
C                                                                       00000220
C      TAPE:                                                            00000230
C          GRAVITY DATA, FORMATTED ACCORDING TO EMR SPECIFICATIONS.     00000240
C      FOR EACH RECORD, THE FOLLOWING IS NEEDED: LATITUDE, LONGITUDE,   00000250
C      FREE AIR ANOMALY, YEAR OF OBSERVATION, HEIGHT ACCURACY FACTOR.   00000260
C                                                                       00000270
      IMPLICIT REAL*8(A-H,O-Z)                                          00000280
      DATA K /'-'/                                                      00000290
      DATA IZ /1H0/                                                     00000300
 101  FORMAT(4F8.2)                                                     00000310
      READ(5,101) XA,XB,YA,YB                                           00000320
      I=1                                                               00000330
      REWIND 3                                                          00000340
  1   READ(3,100,END=2) ID,NUM,IY,IP,P,AL,IC,AHT,IT,IHT,IDAT,DEP,IDEP,ID00000350
     *F,GRAV,DG,BA,TC,IRS                                               00000360
 100  FORMAT(A1,I5,I2,I3,F9.5,F10.5,I1,F7.1,2A1,I1,F7.1,A1,A1,F9.5,F7.2,00000370
     *F7.2,F5.2,A2)                                                     00000380
      IF(P.LT.XA.OR.P.GT.XB) GOTO4                                      00000390
      IF(AL.LT.YA.OR.AL.GT.YB) GOTO4                                    00000400
      N=(IHT-IZ)/16777216                                               00000410
      IF(IHT.EQ.K) N=1                                                  00000420
      IHT=N                                                             00000430
      SNM=12.D0                                                         00000440
      IF(IY.GE.69) GOTO30                                               00000450
      IF(IHT.EQ.1) SNM=0.3                                              00000460
      IF(IHT.EQ.2) SNM=0.9                                              00000470
      IF(IHT.EQ.3) SNM=2.4                                              00000480
      IF(IHT.EQ.4) SNM=9.4                                              00000490
      GOTO31                                                            00000500
  30  CONTINUE                                                          00000510
      IF(IHT.EQ.1) SNM=0.05                                             00000520
      IF(IHT.EQ.2) SNM=0.1                                              00000530
      IF(IHT.EQ.3) SNM=0.3                                              00000540
      IF(IHT.EQ.4) SNM=0.9                                              00000550
      IF(IHT.EQ.5) SNM=2.4                                              00000560
      IF(IHT.EQ.6) SNM=9.4                                              00000570
  31  CONTINUE                                                          00000580
      WRITE(6,200) P,AL,DG,SNM                                          00000590
 200  FORMAT(10X,2F16.6,2F16.2)                                         00000600
      WRITE(12) P,AL,DG,SNM                                             00000610
      I=I+1                                                             00000620
  4   CONTINUE                                                          00000630
      GOTO1                                                             00000640
  2   CONTINUE                                                          00000650
      I=I-1                                                             00000660
      WRITE(6,201) I                                                    00000670
 201  FORMAT(///,10X,'NO. OF POINTS =',I8)                              00000680
      STOP                                                              00000690
C                                                                       00000700
C      THE PROGRAM SORTD IS USED TO SORT THE GRAVITY ANOMALIES IN       00000710
C      ASCENDING ORDER OF LATITUDE                                      00000720
C                                                                       00000730
      END                                                               00000740