nmea-parser/index.js

Parses NMEA sentences.

#!/usr/bin/env node

//NMEA data taken from:
//http://ianrpubs.unl.edu/live/ec157/build/ec157.pdf

var fs = require('fs');
var program = require("commander");

program
    .version('0.0.1')
    .option('-f, --file [option]', 'File to be parsed.')
    .parse(process.argv);

var nmeaGps = fs.createReadStream(program.file);

readTextFile(nmeaGps, parse);

if(!String.prototype.startsWith){
    String.prototype.startsWith = function (str) {
        return !this.indexOf(str);
    }
}

function parse (sentence) {
    var nmea = sentence.split(",");

    var status = (nmea[2] == "A" ? "Ok!" : "Warning");

    var latDeg = parseInt(nmea[3].substring(0, 2));
    var latMin = nmea[3].substring(2);
    var lat = latDeg + (latMin/60);
    var latDirection = nmea[4];

    var lngDeg = parseInt(nmea[5].substring(0, 3));
    var lngMin = nmea[5].substring(3);
    var lng = lngDeg + (lngMin/60);
    var lngDirection = nmea[6];

    console.log(status + " " + lat + "" + latDirection + " " + lng + "" + lngDirection);
    console.log("http://www.google.com/maps/place/" + lat + ",-" + lng + "/@" + lat + ",-" + lng + ",17z");
}

function readTextFile(input, parse) {
    var remaining = '';

    input.on('data', function(data) {
        remaining += data;
        var index = remaining.indexOf('\n');
        while (index > -1) {
            var line = remaining.substring(0, index);
            remaining = remaining.substring(index + 1);
            if(line.startsWith("$GPRMC")) {
                parse(line);
            }
            index = remaining.indexOf('\n');
        }
    });

    input.on('end', function() {
        if (remaining.length > 0 && remaining.startsWith("$GPRMC")) {
            parse(remaining);
        }
    });
}