Convert .ubx data to NMEA data saved by exceel format

This function is mainly used to extract the loosely solution from the .ubx data collected from the ublox receiver. Even for .txt files from GNSSLOGGER of Google, the NMEA solutions can be extracted into the CSV file and the .kml file.

Notes

the thing you need to change/specify is the rcvNmeaPathName in the following matlab code.
latest version (stable)

% By NG Hoi-Fung, Ivan 
% Discription: Convert the NMEA sentence to time, llh data
% Output CSV format: gps time, latitude, longitude, MSL(m), Geoid(m), utc time(yyyymmddHHMMSS.FFF)
% csv file will output to the original path that nmea file directory

clc;
clear;
close all;

GPS_TIME_START = datetime(1980,1,6,0,0,0,0);
leap_second = 18;

nmea_path = 'C:\Users\Administrator\Dropbox\Weisong and Yinhan\Data Collection\2020_1230_14_02_polyu\COM6_201230_060132.ubx'; % input nmea sentence directory
[nmea_dir, exp_name] = fileparts(nmea_path);

support_type = {'$G*GGA','$G*RMC','$G*GLL','$G*BWC'};

% GGA: UTC, Lat, NE, Lon, NE, Fix Quality, No Sat, HDOP, MSL(m), Geoid(m)
% RMC: UTC, Status, Lat, NE, Lon, NE, Speed, Track angle, Date, Magnetic, checksum
% GLL: Lat, NE, Lon, NE, UTC, Date active, checksum
% BWC: UTC, Lat, NE, Lon, NE,bearing(true), bearing(magnetic), dist to waypoint(NM), waypoint id, checksum
% RMB: data status, Cross-track error(NM), Origin waypoint ID, Destination waypoint ID

date_str = {};
S = textread(nmea_path,'%s');
nmea_pos = double.empty(0,4);

for i = 1:length(S)
    type = regexp(S{i}, regexptranslate('wildcard', support_type));
    sup = 0;
    sup = find(~cellfun(@isempty,type));
    k = strfind(S{i},'$GNRMC');
    if k
       disp(''); 
    end
    if ~isempty(sup)
        utc = nan; lat = nan; lon = nan; msl = nan; geoid = nan;
        lat_ = nan; lon_ = nan; date_ = nan;
        lat_factor = 1; lon_factor = 1;
        
        str = S{i};
        str = str(type{sup}:end)
        C = strsplit(str,',', 'CollapseDelimiters',false);
        %         disp('');
        switch(sup)
            case 1 % GGA
                utc = str2double(C{2});
                utc_ = C{2};
                try
                    lat_ = str2double(C{3});
                    if C{4}~='N'; lat_factor = -1; end
                catch
                end
                try
                    lon_ = str2double(C{5});
                    if C{6}~='E'; lon_factor = -1; end
                catch
                end
                try msl = str2double(C{10}); catch, end
                try geoid = str2double(C{12}); catch, end
            case 2 % RMC
                utc = str2double(C{2});
                utc_ = C{2};
                try
                    lat_ = str2double(C{4});
                    if C{5}~='N'; lat_factor = -1; end
                catch
                end
                try
                    lon_ = str2double(C{6});
                    if C{7}~='E'; lon_factor = -1; end
                catch
                end
                try
                    datetime(C{10},'InputFormat','ddMMyy');
                    if isnan(date_); date_ = C{10}; end
                catch
                end
            case 3 % GLL
                utc = str2double(C{6});
                utc_ = C{6};
                try
                    lat_ = str2double(C{2});
                    if C{3}~='N'; lat_factor = -1; end
                catch
                end
                try
                    lon_ = str2double(C{4});
                    if C{5}~='E'; lon_factor = -1; end
                catch
                end
            case 4 % BWC
                utc = str2double(C{2});
                utc_ = C{2};
                try
                    lat_ = str2double(C{3});
                    if C{4}~='N'; lat_factor = -1; end
                catch
                end
                try
                    lon_ = str2double(C{5});
                    if C{6}~='E'; lon_factor = -1; end
                catch
                end
        end
        
        try
            datetime(utc_,'InputFormat','HHmmss.S');
        catch
            utc_ = nan;
        end
        
        if ~isnan(lat_)
            degree = floor(lat_/100);
            minute = floor(lat_ - degree*100)/60;
            second = (lat_ - (degree*100 + floor(lat_ - degree*100)))*60/3600;
            lat = degree + minute + second;
        end
        
        if ~isnan(lon_)
            degree = floor(lon_/100);
            minute = floor(lon_ - degree*100)/60;
            second = (lon_ - (degree*100 + floor(lon_ - degree*100)))*60/3600;
            lon = degree + minute + second;
        end
        
        if isempty(nmea_pos)
            nmea_pos = [utc,nan,nan,nan,nan];
        end
        utc_idx = find(nmea_pos(:,1)==utc);
        if isempty(utc_idx)
            utc_idx = size(nmea_pos,1)+1;
            nmea_pos(utc_idx,:) = [utc,nan,nan,nan,nan];
        end
        if isnan(nmea_pos(utc_idx,2)) && ~isnan(lat); nmea_pos(utc_idx,2)=lat; end
        if isnan(nmea_pos(utc_idx,3)) && ~isnan(lon); nmea_pos(utc_idx,3)=lon; end
        if isnan(nmea_pos(utc_idx,4)) && ~isnan(msl); nmea_pos(utc_idx,4)=msl; end
        if isnan(nmea_pos(utc_idx,5)) && ~isnan(geoid); nmea_pos(utc_idx,5)=geoid; end
        if ~isnan(date_); date_str(utc_idx,1) = {date_}; end
        if ~isnan(utc_); date_str(utc_idx,2) = {utc_}; end
    end
end

empty_date_idx = find(cellfun(@isempty,date_str(:,1)));
date_idx = find(~cellfun(@isempty,date_str(:,1)));
for i = 1:size(empty_date_idx,1)
    [~, store_idx] = min(date_idx - empty_date_idx(i));
    date_str(empty_date_idx(i),1) = date_str(date_idx(store_idx),1);
end
validIdx = find(~isnan(nmea_pos(:,1)));
nmea_pos = nmea_pos(validIdx,:);
date_str = date_str(validIdx,:);
gps_time = zeros(size(date_str,1),1);
utc_time = zeros(size(date_str,1),1);
for i = 1:size(gps_time,1)
    tempt = datetime(strcat(date_str{i,:}),'InputFormat','ddMMyyHHmmss.S');
    gps_time(i) = seconds(tempt - GPS_TIME_START) + leap_second;
    utc_time(i) = str2double(datestr(tempt, 'yyyymmddHHMMSS.FFF'));
end
nmea_pos(:,1) = gps_time;
nmea_pos = [nmea_pos utc_time];
[all_week, all_sow] = time2weektow(nmea_pos(:,1));

% if exist('plot_openstreetmap'); plot_openstreetmap(nmea_pos(:,[2:3])); end
if exist('plot_osm'); plot_osm(nmea_pos(:,[2:3])); end 

% Output format: gps time, latitude, longitude, MSL(m), Geoid(m), utc time(yyyymmddHHMMSS.FFF)
nmea_output = [nmea_dir,'\',exp_name,'_nmea.csv'];
fid = fopen(nmea_output,'w+');
for i = 1:size(nmea_pos,1)
    % fprintf(fid,'%d,%.7f,%.7f,%.1f,%.1f,%.2f\n',nmea_pos(i,:));
    fprintf(fid,'%d,%.1f,%.7f,%.7f,%.1f,%.1f,%.2f\n',all_week(i),all_sow(i),nmea_pos(i,2:end));
end
kmlwrite('COM6_201230_060132.kml',nmea_pos(:,2),nmea_pos(:,3),'Icon',...
    'http://maps.google.com/mapfiles/kml/shapes/shaded_dot.png','IconScale',0.5,'Color',[1,0,0],'Name','  ');
% csvtokml('conventional\data_con.kml',ublox_data,'cyan_dot');
fclose(fid);

file convert_nmea.m

MATLAB code for convert .ubx/txt file to excell file

clc;
clear all;
close all;

% rcvNmeaPathName = 'conventional\COM4_171208_093901.nmea';
%rcvNmeaPathName = 'proposed\COM15_171208_093900.nmea';
% rcvNmeaPathName = 'TST_20180521\raw\XPH_180521_115546.ubx';
rcvNmeaPathName = 'gnss_log_2020_12_29_14_49_15.txt';


% GPSTimeS = 31562;%109000;%[273451];
% GPSTimeE = 35021;%122800;%[274095];

GPSTimeS = 0;%109000;%[273451];
GPSTimeE = 10000000000;%122800;%[274095];

%% Load rcv nmea and time table
nmeaGPSTIndexShift = 1;
nmeaLatIndexShift = 2; 
nmeaLonIndexShift = 4;
nmeaHeightMSIIndexShift = 9;
nmeaHeightGEOIndexShift = 11;
nmeaGPSTIndexShift
UTCGPSshift = 18;
secondsInaDay = 86400;
rcvNmea = textread(rcvNmeaPathName, '%s', 'whitespace', ',');
rcvPosResult = zeros(1,3);
rcvPosResultCount = 0;
gpsTimeShift = fix(GPSTimeE/secondsInaDay)*secondsInaDay;
GPSTime_last = 0;
if GPSTimeE>=0 && GPSTimeS>=0 && GPSTimeE>GPSTimeS
    for rcvNmeaIdx = 1:size(rcvNmea,1)
        if ~isempty(rcvNmea{rcvNmeaIdx, 1})
        if rcvNmea{rcvNmeaIdx, 1}(1,1) == '$'
            %rcvNmeaIdx
            time = str2double(rcvNmea{rcvNmeaIdx + nmeaGPSTIndexShift, 1});
            lat = str2double(rcvNmea{rcvNmeaIdx + nmeaLatIndexShift, 1});
            lon = str2double(rcvNmea{rcvNmeaIdx + nmeaLonIndexShift, 1});
            hour = fix(time/10000);
            minu = fix((time-hour*10000)/100);
            sec = fix(time-hour*10000-minu*100);
            UTCTime = hour*3600 + minu * 60 + sec;
            GPSTime = UTCTime + UTCGPSshift + gpsTimeShift*0;       
            rcvNmea{34071,1}=0;
            height_msl = str2double(rcvNmea{rcvNmeaIdx + nmeaHeightMSIIndexShift, 1});
%             height_geo = str2double(rcvNmea{rcvNmeaIdx + nmeaHeightGEOIndexShift, 1});
            

            if (GPSTime>=GPSTimeS&&GPSTime<=GPSTimeE) && (GPSTime ~= GPSTime_last)
                rcvPosResultCount = rcvPosResultCount+1;
                latDeg = fix(lat/100);
                latMin = (lat-latDeg*100);
                latInDegrees = latDeg+latMin/60.0;               
                
                lonDeg = fix(lon/100);
                lonMin = (lon-lonDeg*100);
                lonInDegrees = lonDeg+lonMin/60.0;
                
                rcvPosResult (rcvPosResultCount ,1) = GPSTime;
                rcvPosResult (rcvPosResultCount ,2) = latInDegrees;
                rcvPosResult (rcvPosResultCount ,3) = lonInDegrees;
                rcvPosResult (rcvPosResultCount ,4) = height_msl;
%                 rcvPosResult (rcvPosResultCount ,5) = height_geo;
                GPSTime_last = GPSTime;
            end
        end
        end        
    end
end
idn = find(rcvPosResult(:,2) > 22);
rcvPosResult = rcvPosResult(idn,:);

idm = find(rcvPosResult(:,2) < 30);
rcvPosResult = rcvPosResult(idm,:);
dlmwrite('gnss_log_2020_12_29_14_49_15.csv', rcvPosResult, 'precision', '%12.8f');

ublox_data = csvread('gnss_log_2020_12_29_14_49_15.csv');

kmlwrite('gnss_log_2020_12_29_14_49_15.kml',ublox_data(:,2),ublox_data(:,3),'Icon',...
    'http://maps.google.com/mapfiles/kml/shapes/shaded_dot.png','IconScale',0.5,'Color',[1,0,0],'Name','  ');
% csvtokml('conventional\data_con.kml',ublox_data,'cyan_dot');

Reference

(slides))
Google Code Styleguide
C++ tutorials

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Author: Weisong Wen, PhD Candidate in Hong Kong Polytechnic University.
Email: weisongwen@weisongwen
Affiliation: Intelligent Positioning and Navigation Laboratory

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Convert .ubx data to NMEA data saved by exceel format

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