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function [dtsvS] = GpsEph2Dtsv(gpsEph,tS)
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%[dtsvS] = GpsEph2Dtsv(gpsEph,tS)
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%
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% Calculate satellite clock bias
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% Inputs:
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% gpsEph = vector of GPS ephemeris structures defined in ReadRinexNav
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% tS GPS time of week (secs) at time of transmission, calculate this as:
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% tS = trx - PR/c,
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% where trx = time of reception (receiver clock)
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% PR = pseudorange
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%
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% tS may be a vector, gpsEph is a structure or vector of structures
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% If gpsEph is a vector then t must have the same number of rows as gpsEph
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% tS(i) is interpreted as being associated with gpsEph(i,:)
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% If gpsEph is a single structure then tS may be any length
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%
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% Outputs:
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% dtsvS = sat clock bias (seconds). GPS time = satellite time - dtsvS
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% length(dtsvS) = length(tS)
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%
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% See IS-GPS-200 and RTCM Paper 99-92 SC104-88 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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%% Check size of inputs
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if min(size(tS))>1
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error('tS must be a vector or a scalar, not a matrix')
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end
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tS=tS(:)';%make t a row vector, to match [gpsEph.*] vectors below
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pt=length(tS);
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[p]=length(gpsEph);
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if (p>1 && pt~=p),
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error('If gpsEph is a vector tS must be a vector with #rows = length(gpsEph),\n')
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end
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%%
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%%Extract the necessary variables from gpsEph
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TGD = [gpsEph.TGD];
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Toc = [gpsEph.Toc];
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af2 = [gpsEph.af2];
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af1 = [gpsEph.af1];
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af0 = [gpsEph.af0];
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Delta_n = [gpsEph.Delta_n];
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M0 = [gpsEph.M0];
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e = [gpsEph.e];
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Asqrt = [gpsEph.Asqrt];
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Toe = [gpsEph.Toe];
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%%
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%%Calculate dependent variables ------------------------------------------------
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tk = tS - Toe; %time since time of applicability
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I = find(tk > 302400.0);
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if any(I), tk(I) = tk(I)-GpsConstants.WEEKSEC; end,
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I = find(tk < -302400.0);
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if (I), tk(I) = tk(I)+GpsConstants.WEEKSEC; end,
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A = Asqrt.^2; %semi-major axis of orbit
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n0=sqrt(GpsConstants.mu./(A.^3)); %Computed mean motion (rad/sec)
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n=n0+Delta_n; %Corrected Mean Motion
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Mk=M0+n.*tk; %Mean Anomaly
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Ek=Kepler(Mk,e); %Solve Kepler's equation for eccentric anomaly
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%%
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%%Calculate satellite clock bias (See ICD-GPS-200 20.3.3.3.3.1) ----------------
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dt = tS - Toc;
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I = find(dt > 302400.0);
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if any(I), dt(I) = dt(I)-GpsConstants.WEEKSEC; end,
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I = find(dt < -302400.0);
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if (I), dt(I) = dt(I)+GpsConstants.WEEKSEC; end,
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dtsvS = af0 + af1.*dt + af2.*(dt.^2) + ...
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GpsConstants.FREL.*e.*Asqrt.*sin(Ek) -TGD;
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end % end of function GpsEph2Dtsv
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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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