gdran.f
74 lines
| 2.5 KiB
| text/x-fortran
|
FortranFixedLexer
| r0 | C $Id: gdran.f 3304 2011-01-17 15:25:59Z brideout $ | |||
| C | ||||
| DOUBLE PRECISION FUNCTION GDRAN(SR,SLATGC,SLON,AZ,EL,ALT) | ||||
| C | ||||
| C GDRAN uses a half-interval (binary) search technique to determine | ||||
| C the geodetic range to a point of observation given in terms of | ||||
| C azimuth, elevation, and geodetic altitude. | ||||
| C | ||||
| C Input: | ||||
| C SR - radial distance of station from center of earth | ||||
| C SLATGC - station geocentric latitude | ||||
| C SLON - station longitude | ||||
| C AZ - radar azimuth | ||||
| C EL - radar elevation | ||||
| C ALT - geodetic altitude | ||||
| C | ||||
| C harris fortran 77 | ||||
| C rgm - 8/85 | ||||
| C | ||||
| C .. Scalar Arguments .. | ||||
| DOUBLE PRECISION ALT,AZ,EL,SLATGC,SLON,SR | ||||
| C .. | ||||
| C .. Local Scalars .. | ||||
| DOUBLE PRECISION ALT1,ALT2,GCLAT,GDALT,GDLAT,GLONG,PR,R1,R2,RFRST, | ||||
| * TINTER | ||||
| C .. | ||||
| C .. External Functions .. | ||||
| DOUBLE PRECISION RFUN | ||||
| EXTERNAL RFUN | ||||
| C .. | ||||
| C .. External Subroutines .. | ||||
| EXTERNAL CONVRT,POINT | ||||
| C .. | ||||
| C .. Intrinsic Functions .. | ||||
| INTRINSIC ABS,SIGN | ||||
| C .. | ||||
| C | ||||
| C determine two ranges which bound the actual range. the first | ||||
| C range is obtained by making a spherical earth range calculation | ||||
| C using the supplied station radius. this range will be on one | ||||
| C side or the other of the actual range and will be added to or | ||||
| C subtracted from to determine the second range until the second | ||||
| C range is on the opposite side of the actual range as the first | ||||
| C range (whew!). | ||||
| C | ||||
| R1 = RFUN(SR,EL,ALT) | ||||
| R2 = R1 | ||||
| CALL POINT(SR,SLATGC,SLON,AZ,EL,R2,PR,GCLAT,GLONG) | ||||
| CALL CONVRT(2,GDLAT,ALT1,GCLAT,PR) | ||||
| 10 CONTINUE | ||||
| R2 = R2 + SIGN(1.D0,ALT-ALT1) | ||||
| CALL POINT(SR,SLATGC,SLON,AZ,EL,R2,PR,GCLAT,GLONG) | ||||
| CALL CONVRT(2,GDLAT,ALT2,GCLAT,PR) | ||||
| IF (SIGN(1.D0,ALT-ALT1).EQ.SIGN(1.D0,ALT-ALT2)) GO TO 10 | ||||
| C | ||||
| C use the center of the range boundary as a first guess. the | ||||
| C half-interval is initially 1/4 of the total range boundary. | ||||
| C | ||||
| RFRST = (R1+R2)/2.D0 | ||||
| TINTER = ABS(R2-R1)/4.D0 | ||||
| C | ||||
| C add to or subtract from the current range guess the current | ||||
| C half-interval, halving the half-interval on each iteration until | ||||
| C the actual range is approached to within a tolerance of .01 km. | ||||
| C | ||||
| 20 CONTINUE | ||||
| CALL POINT(SR,SLATGC,SLON,AZ,EL,RFRST,PR,GCLAT,GLONG) | ||||
| CALL CONVRT(2,GDLAT,GDALT,GCLAT,PR) | ||||
| RFRST = RFRST + SIGN(TINTER,ALT-GDALT) | ||||
| TINTER = TINTER/2.D0 | ||||
| IF (ABS(GDALT-ALT).GE.1.D-2) GO TO 20 | ||||
| GDRAN = RFRST | ||||
| RETURN | ||||
| END | ||||
