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function [xM,dtsvS,vMps,dtsvSDot] = GpsEph2Pvt(gpsEph,gpsTime) |
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%[xM,dtsvS,vMps,dtsvSDot] = GpsEph2Pvt(gpsEph,gpsTime) |
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% |
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% Calculate sv coordinates, in ECEF frame, sv clock bias, and sv velocity |
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% Inputs: |
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% gpsEph: vector of ephemeris structures, as defined in ReadRinexEph.m |
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% |
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% gpsTime = [gpsWeek, ttxSec]: GPS time at time of transmission, ttx |
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% ttx = trx - PR/c - dtsvS, where trx is time of reception (receiver clock), |
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% dtsvS is the satellite clock error (seconds), can be computed in advance |
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% using eph2dtsv.m or iterating this function: gps time = sat time - dtsvS |
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% gpsWeek, ttxSec must be vectors of length(gpsEph), |
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% |
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% outputs: |
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% xM = [i,j,k] matrix of coordinates of satellites (ecef meters) |
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% dtsvS = vector of satellite clock error (seconds) |
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% vMps = [i,j,k] matrix of satellite velocity (ecef m/s) |
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% dtsvSDot = vector of satellite clock error rate (seconds/second) |
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% The row dimension of xM, dtsvS, vMps, dtsvSDot = length(gpsEph) |
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% |
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% xM and vMps are the satellite positions and velocities |
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% at time ttxSec, in terms of ecef coords at the same time |
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% Use FlightTimeCorrection.m to get xM & vMps in ecef coord at time of reception |
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% |
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% functions called: GpsEph2Xyz.m |
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% |
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% See IS-GPS-200 for details of data |
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%Author: Frank van Diggelen |
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%Open Source code for processing Android GNSS Measurements |
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vMps = []; dtsvSDot = []; |
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[xM,dtsvS]=GpsEph2Xyz(gpsEph,gpsTime); |
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if isempty(xM) |
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return |
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end |
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%compute velocity from delta position & dtsvS at (t+0.5) - (t-0.5) |
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%This is better than differentiating, because both the orbital and relativity |
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%terms have nonlinearities that are not easily differentiable |
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t1 = [gpsTime(:,1), gpsTime(:,2)+0.5]; %time + 0.5 seconds |
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[xPlus,dtsvPlus] = GpsEph2Xyz(gpsEph,t1); |
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t1 = [gpsTime(:,1), gpsTime(:,2)-0.5]; %time - 0.5 seconds |
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[xMinus,dtsvMinus]= GpsEph2Xyz(gpsEph,t1); |
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vMps = xPlus - xMinus; |
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dtsvSDot = dtsvPlus - dtsvMinus; |
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end %end of function GpsEph2Pvt |
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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% Copyright 2016 Google Inc. |
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% |
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% Licensed under the Apache License, Version 2.0 (the "License"); |
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% you may not use this file except in compliance with the License. |
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% You may obtain a copy of the License at |
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% |
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% http://www.apache.org/licenses/LICENSE-2.0 |
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% |
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% Unless required by applicable law or agreed to in writing, software |
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% distributed under the License is distributed on an "AS IS" BASIS, |
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% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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% See the License for the specific language governing permissions and |
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% limitations under the License. |
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