前面有C代表是注释,电离层克罗布切模型 C Last change: OO 20 Nov 2000 11:22 am SUBROUTINE KLOBUCHAR(fi,lambda,elev,azimuth,tow,alfa,beta,dIon1) C ================================================================== C Subroutine for computing an Ionospheric range correction for the * C GPS L1 frequency from the parameters broadcasted in the GPS * C Navigation Message. * C ================================================================== C References: * C Klobuchar, J.A., (1996) "Ionosphercic Effects on GPS", in * C Parkinson, Spilker (ed), "Global Positioning System Theory and * C Applications, pp.513-514. * C ICD-GPS-200, Rev. C, (1997), pp. 125-128 * C NATO, (1991), "Technical Characteristics of the NAVSTAR GPS", * C pp. A-6-31 - A-6-33 * C ================================================================== C Author : Ola Ovstedal, Department of Mapping Sciences * C Agricultural University of Norway * C Date : 06.03.2000 Last modified : 20.11.2000 * C ================================================================== C Input : * C fi : Geodetic latitude of receiver (deg) * C lambda : Geodetic longitude of receiver (deg) * C elev : Elevation angle of satellite (deg) * C azimuth : Geodetic azimuth of satellite (deg) * C tow : Time of Week (sec) * C alfa(4) : The coefficients of a cubic equation * C representing the amplitude of the vertical * C dalay (4 coefficients - 8 bits each) * C beta(4) : The coefficients of a cubic equation * C representing the period of the model * C (4 coefficients - 8 bits each) * C Output: * C dIon1 : Ionospheric slant range correction for * C the L1 frequency (metre) * C ================================================================== C Called by : * C * C Subroutines called: * C Internal: * C External: * C Include files : * C ================================================================== C Changes: * C 20.11.2000 : Different constants assigned in subroutine so that * C the subroutine is self-contained (for GPS-TOOLBOX) * C ================================================================== IMPLICIT NONE C REAL*8 alfa(4),beta(4),fi,lambda,elev,e,azimuth,a,tow,t, + dIon1,psi,lat_i,long_i,lat_m,sf,PER,AMP,x,deg2semi, + semi2rad,deg2rad,pi,c pi = 3.1415926535898D0 ! WGS-84 value of pi c = 2.99792458D8 ! speed of light deg2semi = 1.D0/180.D0 ! degees to semisircles semi2rad = pi ! semisircles to radians deg2rad = pi/180.D0 ! degrees to radians a = azimuth*deg2rad ! asimuth in radians e = elev*deg2semi ! elevation angle in ! semicircles psi = 0.0137D0 / (e+0.11D0) - 0.022D0 ! Earth Centered angle lat_i = fi*deg2semi + psi*DCOS(a) ! Subionospheric lat IF(lat_i .GT. 0.416D0) THEN lat_i = 0.416D0 ELSEIF(lat_i .LT. -0.416) THEN lat_i = -0.416D0 ENDIF ! Subionospheric long long_i = lambda*deg2semi + (psi*DSIN(a)/DCOS(lat_i*semi2rad)) ! Geomagnetic latitude lat_m = lat_i + 0.0D0*DCOS((long_i-1.617D0)*semi2rad) t = 4.32D4*long_i + tow t = DMOD(t,800.D0) ! Seconds of day IF(t .GT. 800.D0) t = t - 800.D0 IF(t .LT. 0.D0) t = t + 800.D0 sf = 1.D0 + 16.D0*(0.53D0-e)**3 ! Slant factor ! Period of model PER = beta(1) + beta(2)*lat_m + beta(3)*lat_m**2 +beta(4)*lat_m**3 IF(PER .LT. 72000.D0) PER = 72000.D0 x = 2.D0*pi*(t-50400.D0) / PER ! Phase of the model ! (Max at 14.00 = ! 50400 sec local time) ! Amplitud of the model AMP = alfa(1) + alfa(2)*lat_m + alfa(3)*lat_m**2 +alfa(4)*lat_m**3 IF(AMP .LT. 0.D0) AMP = 0.D0 ! Ionospheric corr. IF(DABS(x) .GT. 1.57D0) THEN dIon1 = sF * (5.D-9) ELSE dIon1 = sF * (5.D-9 + AMP*(1.D0 - x*x/2.D0 + x*x*x*x/24.D0)) ENDIF dIon1 = c * dIon1 RETURN END 请用非fortran语言实现。