www.pudn.com > GNSS_SDR.zip > postNavigation.asv, change:2008-09-24,size:12612b

function [navSolutions, eph] = postNavigation(trackResults, settings) %Function calculates navigation solutions for the receiver (pseudoranges, %positions). At the end it converts coordinates from the WGS84 system to %the UTM, geocentric or any additional coordinate system. % %[navSolutions, eph] = postNavigation(trackResults, settings) % % Inputs: % trackResults - results from the tracking function (structure % array). % settings - receiver settings. % Outputs: % navSolutions - contains measured pseudoranges, receiver % clock error, receiver coordinates in several % coordinate systems (at least ECEF and UTM). % eph - received ephemerides of all SV (structure array). %-------------------------------------------------------------------------- % SoftGNSS v3.0 % % Copyright (C) Darius Plausinaitis % Written by Darius Plausinaitis with help from Kristin Larson %-------------------------------------------------------------------------- %This program is free software; you can redistribute it and/or %modify it under the terms of the GNU General Public License %as published by the Free Software Foundation; either version 2 %of the License, or (at your option) any later version. % %This program is distributed in the hope that it will be useful, %but WITHOUT ANY WARRANTY; without even the implied warranty of %MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the %GNU General Public License for more details. % %You should have received a copy of the GNU General Public License %along with this program; if not, write to the Free Software %Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, %USA. %-------------------------------------------------------------------------- %CVS record: %$Id: postNavigation.m,v 1.1.2.22 2006/08/09 17:20:11 dpl Exp $ %% Check is there enough data to obtain any navigation solution =========== % It is necessary to have at least three subframes (number 1, 2 and 3) to % find satellite coordinates. Then receiver position can be found too. % The function requires all 5 subframes, because the tracking starts at % arbitrary point. Therefore the first received subframes can be any three % from the 5. % One subframe length is 6 seconds, therefore we need at least 30 sec long % record (5 * 6 = 30 sec = 30000ms). We add extra seconds for the cases, % when tracking has started in a middle of a subframe. %%%%%%%%% the below "if" section changed by Jiffer at 2008-09-24 %%%%%%%%%%%%% %if (settings.msToProcess < 36000) || (sum([trackResults.status] ~= '-') < 4) % Show the error message and exit % disp('Record is to short or too few satellites tracked. Exiting!'); % navSolutions = []; % eph = []; % return %end %%%%%%%%% the end of the change %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% Find preamble start positions ========================================== [subFrameStart, activeChnList] = findPreambles(trackResults, settings); %% Decode ephemerides ===================================================== for channelNr = activeChnList %=== Convert tracking output to navigation bits ======================= %--- Copy 5 sub-frames long record from tracking output --------------- navBitsSamples = trackResults(channelNr).I_P(subFrameStart(channelNr) - 20 : ... subFrameStart(channelNr) + (1500 * 20) -1)'; %--- Group every 20 vales of bits into columns ------------------------ navBitsSamples = reshape(navBitsSamples, ... 20, (size(navBitsSamples, 1) / 20)); %--- Sum all samples in the bits to get the best estimate ------------- navBits = sum(navBitsSamples); %--- Now threshold and make 1 and 0 ----------------------------------- % The expression (navBits > 0) returns an array with elements set to 1 % if the condition is met and set to 0 if it is not met. navBits = (navBits > 0); %--- Convert from decimal to binary ----------------------------------- % The function ephemeris expects input in binary form. In Matlab it is % a string array containing only "0" and "1" characters. navBitsBin = dec2bin(navBits); %=== Decode ephemerides and TOW of the first sub-frame ================ [eph(trackResults(channelNr).PRN), TOW] = ... ephemeris(navBitsBin(2:1501)', navBitsBin(1)); %--- Exclude satellite if it does not have the necessary nav data ----- if (isempty(eph(trackResults(channelNr).PRN).IODC) || ... isempty(eph(trackResults(channelNr).PRN).IODE_sf2) || ... isempty(eph(trackResults(channelNr).PRN).IODE_sf3)) %--- Exclude channel from the list (from further processing) ------ activeChnList = setdiff(activeChnList, channelNr); end end %% Check if the number of satellites is still above 3(blocked by Jffer at 2008-09-24) ===================== %if (isempty(activeChnList) || (size(activeChnList, 2) < 4)) % Show error message and exit % disp('Too few satellites with ephemeris data for postion calculations. Exiting!'); % navSolutions = []; % eph = []; % return %end %% Initialization ========================================================= % Set the satellite elevations array to INF to include all satellites for % the first calculation of receiver position. There is no reference point % to find the elevation angle as there is no receiver position estimate at % this point. satElev = inf(1, settings.numberOfChannels); % Save the active channel list. The list contains satellites that are % tracked and have the required ephemeris data. In the next step the list % will depend on each satellite's elevation angle, which will change over % time. readyChnList = activeChnList; transmitTime = TOW; %%Save subfreamstart by Jeffer navSolutions.subFrameStart=subFrameStart; %########################################################################## %# Do the satellite and receiver position calculations # %########################################################################## %% Initialization of current measurement ================================== for currMeasNr = 1:fix((settings.msToProcess - max(subFrameStart)) / ... settings.navSolPeriod) % Exclude satellites, that are belove elevation mask activeChnList = intersect(find(satElev >= settings.elevationMask), ... readyChnList); % Save list of satellites used for position calculation navSolutions.channel.PRN(activeChnList, currMeasNr) = ... [trackResults(activeChnList).PRN]; % These two lines help the skyPlot function. The satellites excluded % do to elevation mask will not "jump" to possition (0,0) in the sky % plot. navSolutions.channel.el(:, currMeasNr) = ... NaN(settings.numberOfChannels, 1); navSolutions.channel.az(:, currMeasNr) = ... NaN(settings.numberOfChannels, 1); %% Find pseudoranges ====================================================== navSolutions.channel.rawP(:, currMeasNr) = calculatePseudoranges(... trackResults, ... subFrameStart + settings.navSolPeriod * (currMeasNr-1), ... activeChnList, settings); %% Find satellites positions and clocks corrections ======================= [satPositions, satClkCorr] = satpos(transmitTime, ... [trackResults(activeChnList).PRN], ... eph, settings); %% Save the transmitTime navSolutions.transmitTime(currMeasNr)=transmitTime; %% Find receiver position ================================================= % 3D receiver position can be found only if signals from more than 3 % satellites are available if size(activeChnList, 2) > 3 %=== Calculate receiver position ================================== [xyzdt, ... navSolutions.channel.el(activeChnList, currMeasNr), ... navSolutions.channel.az(activeChnList, currMeasNr), ... navSolutions.DOP(:, currMeasNr)] = ... leastSquarePos(satPositions, ... navSolutions.channel.rawP(activeChnList, currMeasNr)' + satClkCorr * settings.c, ... settings); %--- Save results ------------------------------------------------- navSolutions.X(currMeasNr) = xyzdt(1); navSolutions.Y(currMeasNr) = xyzdt(2); navSolutions.Z(currMeasNr) = xyzdt(3); navSolutions.dt(currMeasNr) = xyzdt(4); % Update the satellites elevations vector satElev = navSolutions.channel.el(:, currMeasNr); %=== Correct pseudorange measurements for clocks errors =========== navSolutions.channel.correctedP(activeChnList, currMeasNr) = ... navSolutions.channel.rawP(activeChnList, currMeasNr) + ... satClkCorr' * settings.c + navSolutions.dt(currMeasNr); %% Coordinate conversion ================================================== %=== Convert to geodetic coordinates ============================== [navSolutions.latitude(currMeasNr), ... navSolutions.longitude(currMeasNr), ... navSolutions.height(currMeasNr)] = cart2geo(... navSolutions.X(currMeasNr), ... navSolutions.Y(currMeasNr), ... navSolutions.Z(currMeasNr), ... 5); %=== Convert to UTM coordinate system ============================= navSolutions.utmZone = findUtmZone(navSolutions.latitude(currMeasNr), ... navSolutions.longitude(currMeasNr)); [navSolutions.E(currMeasNr), ... navSolutions.N(currMeasNr), ... navSolutions.U(currMeasNr)] = cart2utm(xyzdt(1), xyzdt(2), ... xyzdt(3), ... navSolutions.utmZone); else % if size(activeChnList, 2) > 3 %--- There are not enough satellites to find 3D position ---------- disp([' Measurement No. ', num2str(currMeasNr), ... ': Not enough information for position solution.']); %--- Set the missing solutions to NaN. These results will be %excluded automatically in all plots. For DOP it is easier to use %zeros. NaN values might need to be excluded from results in some %of further processing to obtain correct results. navSolutions.X(currMeasNr) = NaN; navSolutions.Y(currMeasNr) = NaN; navSolutions.Z(currMeasNr) = NaN; navSolutions.dt(currMeasNr) = NaN; navSolutions.DOP(:, currMeasNr) = zeros(5, 1); navSolutions.latitude(currMeasNr) = NaN; navSolutions.longitude(currMeasNr) = NaN; navSolutions.height(currMeasNr) = NaN; navSolutions.E(currMeasNr) = NaN; navSolutions.N(currMeasNr) = NaN; navSolutions.U(currMeasNr) = NaN; navSolutions.channel.az(activeChnList, currMeasNr) = ... NaN(1, length(activeChnList)); navSolutions.channel.el(activeChnList, currMeasNr) = ... NaN(1, length(activeChnList)); % TODO: Know issue. Satellite positions are not updated if the % satellites are excluded do to elevation mask. Therefore rasing % satellites will be not included even if they will be above % elevation mask at some point. This would be a good place to % update positions of the excluded satellites. end % if size(activeChnList, 2) > 3 %=== Update the transmit time ("measurement time") ==================== transmitTime = transmitTime + settings.navSolPeriod / 1000; end %for currMeasNr...