GPS nmea GPX (or KLM) converter for Google Maps

This script take large amount of GPS data in nmea format and convert into gpx format to import into Google maps.

I had large amount of data coming from a trip to Iceland and I wanted quicly import it on Google My Maps.

Google has a limit of 5 MB but my data was 90 MB.

To reduce the data the script

• only export latitude and longitude
• approximae the latitude and longitude values reducing the number of decimal digit
• skeep points

There are two variables that you can adjust to get an putput file smaller than 5 MB. In my case the best compromise was

• savePointsEvery = 4
• precision = 6

This generate an ouput file of 4,5 MB

Using instead

• savePointsEvery = 4
• precision = 6

The output file was 6 MB

The output files are in the folder data.

Source

Find the source at https://github.com/lucamug/gps-converter

Example

This is the result after imported in Google Maps:

Source

	// gps-converter by lucamug
	// more info at
	// https://github.com/lucamug/gps-converter
	// https://coding-and-design.blogspot.de/2016/11/gps-nmea-gpx-or-klm-converter-for.html
	var fs = require('fs'),
	folderOriginalData = 'data/original-gps-data/',
	folderOutputData = 'data/',
	r = [],
	savePointsEvery = 4,
	precision = 6,
	files = fs.readdirSync(folderOriginalData),
	ouputFileName = folderOutputData + "output." + savePointsEvery + "." + precision + ".gpx";
	for (var j in files.sort()) {
	var file = files[j];
	r.push(processThisFile(file));
	// break;
	}
	fs.writeFileSync(ouputFileName, [
	'<?xml version="1.0"?>',
	'<gpx creator="lucamug https://github.com/lucamug/gps-converter" version="1.0" xmlns="http://www.topografix.com/GPX/1/0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.topografix.com/GPX/1/0 http://www.topografix.com/GPX/1/0/gpx.xsd">',
	'<trk>',
	'<name>All</name>',
	'<trkseg>',
	r.join(''),
	'</trkseg>',
	'</trk>',
	'</gpx>',
	].join(''));
	console.log("Check the output in " + ouputFileName);
	function processThisFile(filename) {
	var array = fs.readFileSync(folderOriginalData + filename).toString().split("\n");
	var c = 0;
	var r = [];
	for (var i in array) {
	var row = array[i];
	if (row.match(/^\$GPRMC/)) {
	c++;
	if (!(c % savePointsEvery)) {
	var ll = getLatLng(row);
	r.push([
	'<trkpt lat="' + ll.lat + '" lon="' + ll.lon + '">',
	'</trkpt>',
	].join(''));
	}
	// break;
	}
	}
	return r;
	}
	function getLatLng(d) {
	// Example of nmea
	// $GPRMC,002516.000,A,6358.0464,N,02234.5556,W,1.69,324.78,290812,,,A*72
	var nmea = d.split(",");
	var coord, direction, days, minutes, lat, lon;
	// LAT: North South
	coord = nmea[3];
	direction = nmea[4];
	days = coord.substring(0, 2);
	minutes = coord.substring(2, 10);
	lat = toDD(days, minutes, direction);
	// LON: East West
	coord = nmea[5];
	direction = nmea[6];
	days = coord.substring(0, 3);
	minutes = coord.substring(3, 11);
	lon = toDD(days, minutes, direction);
	return { lat: lat, lon: lon };
	}
	function toDD(degrees, minutes, direction) {
	var out = parseInt(degrees) + (parseFloat(minutes) / 60);
	if (direction == "S" || direction == "W") {
	out = out * -1.0;
	}
	return out.toFixed(precision);
	}

view raw gps-converter.js hosted with ❤ by GitHub

Others

Online converter:

http://www.gpsvisualizer.com/convert_input