mirror of https://github.com/gnss-sdr/gnss-sdr
99 lines
2.8 KiB
Matlab
99 lines
2.8 KiB
Matlab
function ddr = tropo(sinel, hsta, p, tkel, hum, hp, htkel, hhum)
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%TROPO Calculation of tropospheric correction.
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% The range correction ddr in m is to be subtracted from
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% pseudo-ranges and carrier phases
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%
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%ddr = tropo(sinel, hsta, p, tkel, hum, hp, htkel, hhum);
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%
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% Inputs:
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% sinel - sin of elevation angle of satellite
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% hsta - height of station in km
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% p - atmospheric pressure in mb at height hp
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% tkel - surface temperature in degrees Kelvin at height htkel
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% hum - humidity in % at height hhum
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% hp - height of pressure measurement in km
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% htkel - height of temperature measurement in km
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% hhum - height of humidity measurement in km
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%
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% Outputs:
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% ddr - range correction (meters)
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%
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% Reference
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% Goad, C.C. & Goodman, L. (1974) A Modified Tropospheric
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% Refraction Correction Model. Paper presented at the
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% American Geophysical Union Annual Fall Meeting, San
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% Francisco, December 12-17
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% A Matlab reimplementation of a C code from driver.
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% Kai Borre 06-28-95
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%
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% CVS record:
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% $Id: tropo.m,v 1.1.1.1.2.4 2006/08/22 13:46:00 dpl Exp $
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%==========================================================================
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a_e = 6378.137; % semi-major axis of earth ellipsoid
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b0 = 7.839257e-5;
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tlapse = -6.5;
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tkhum = tkel + tlapse*(hhum-htkel);
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atkel = 7.5*(tkhum-273.15) / (237.3+tkhum-273.15);
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e0 = 0.0611 * hum * 10^atkel;
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tksea = tkel - tlapse*htkel;
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em = -978.77 / (2.8704e6*tlapse*1.0e-5);
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tkelh = tksea + tlapse*hhum;
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e0sea = e0 * (tksea/tkelh)^(4*em);
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tkelp = tksea + tlapse*hp;
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psea = p * (tksea/tkelp)^em;
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if sinel < 0
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sinel = 0;
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end
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tropo = 0;
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done = 'FALSE';
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refsea = 77.624e-6 / tksea;
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htop = 1.1385e-5 / refsea;
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refsea = refsea * psea;
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ref = refsea * ((htop-hsta)/htop)^4;
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while 1
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rtop = (a_e+htop)^2 - (a_e+hsta)^2*(1-sinel^2);
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% check to see if geometry is crazy
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if rtop < 0
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rtop = 0;
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end
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rtop = sqrt(rtop) - (a_e+hsta)*sinel;
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a = -sinel/(htop-hsta);
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b = -b0*(1-sinel^2) / (htop-hsta);
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rn = zeros(8,1);
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for i = 1:8
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rn(i) = rtop^(i+1);
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end
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alpha = [2*a, 2*a^2+4*b/3, a*(a^2+3*b),...
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a^4/5+2.4*a^2*b+1.2*b^2, 2*a*b*(a^2+3*b)/3,...
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b^2*(6*a^2+4*b)*1.428571e-1, 0, 0];
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if b^2 > 1.0e-35
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alpha(7) = a*b^3/2;
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alpha(8) = b^4/9;
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end
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dr = rtop;
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dr = dr + alpha*rn;
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tropo = tropo + dr*ref*1000;
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if done == 'TRUE '
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ddr = tropo;
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break;
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end
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done = 'TRUE ';
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refsea = (371900.0e-6/tksea-12.92e-6)/tksea;
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htop = 1.1385e-5 * (1255/tksea+0.05)/refsea;
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ref = refsea * e0sea * ((htop-hsta)/htop)^4;
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end;
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%%%%%%%%% end tropo.m %%%%%%%%%%%%%%%%%%%
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