Converting latitude and longitude to decimal values

Question

I have GPS information presented in the form:

36°57'9" N 110°4'21" W

I can use the javascript functions of Chris Veness to convert degrees, minutes and seconds to numeric degrees, but first need to parse the GPS info into the individual latitude and longitude strings (with NSEW suffixes). I have read related posts on stackoverflow, but am not a regex expert (nor a programmer) and need some help with the parsing function. What's the best way to parse this string into latitude and longitude for use in the conversion function?

The result of all this will be a Web link that one can click on to see a Google map representation of location.

Answer 1

To parse your input use the following.

function ParseDMS(input) {
    var parts = input.split(/[^\d\w]+/);
    var lat = ConvertDMSToDD(parts[0], parts[1], parts[2], parts[3]);
    var lng = ConvertDMSToDD(parts[4], parts[5], parts[6], parts[7]);
}

The following will convert your DMS to DD

function ConvertDMSToDD(degrees, minutes, seconds, direction) {
    var dd = degrees + minutes/60 + seconds/(60*60);

    if (direction == "S" || direction == "W") {
        dd = dd * -1;
    } // Don't do anything for N or E
    return dd;
}

So your input would produce the following:

36°57'9" N  = 36.9525000
110°4'21" W = -110.0725000

Decimal coordinates can be fed into google maps to get points via GLatLng(lat, lng) (Google Maps API)

Answer 2

Corrected the above functions and made the output an object.

function ParseDMS(input) {
    var parts = input.split(/[^\d\w\.]+/);    
    var lat = ConvertDMSToDD(parts[0], parts[2], parts[3], parts[4]);
    var lng = ConvertDMSToDD(parts[5], parts[7], parts[8], parts[9]);

    return {
        Latitude : lat,
        Longitude: lng,
        Position : lat + ',' + lng
    }
}


function ConvertDMSToDD(degrees, minutes, seconds, direction) {   
    var dd = Number(degrees) + Number(minutes)/60 + Number(seconds)/(60*60);

    if (direction == "S" || direction == "W") {
        dd = dd * -1;
    } // Don't do anything for N or E
    return dd;
}

Answer 3

My tweaked version coerces the string parts into Numbers so that they can actually be added together rather than concatenated. It also handles decimal values which are common for the Seconds component:

function ParseDMS(input) {
    var parts = input.split(/[^\d\w\.]+/);
    var lat = ConvertDMSToDD(parts[0], parts[1], parts[2], parts[3]);
    var lng = ConvertDMSToDD(parts[4], parts[5], parts[6], parts[7]);
}

The following will convert your DMS to DD

function ConvertDMSToDD(degrees, minutes, seconds, direction) {
    var dd = Number(degrees) + Number(minutes)/60 + Number(seconds)/(60*60);

    if (direction == "S" || direction == "W") {
        dd = dd * -1;
    } // Don't do anything for N or E
    return dd;
}

Answer 4

here is my take on this:

function parse_gps( input ) {

if( input.indexOf( 'N' ) == -1 && input.indexOf( 'S' ) == -1 &&
    input.indexOf( 'W' ) == -1 && input.indexOf( 'E' ) == -1 ) {
    return input.split(',');
}

var parts = input.split(/[°'"]+/).join(' ').split(/[^\w\S]+/);

var directions = [];
var coords = [];
var dd = 0;
var pow = 0;

for( i in parts ) {

    // we end on a direction
    if( isNaN( parts[i] ) ) {

        var _float = parseFloat( parts[i] );

        var direction = parts[i];

        if( !isNaN(_float ) ) {
            dd += ( _float / Math.pow( 60, pow++ ) );
            direction = parts[i].replace( _float, '' );
        }

        direction = direction[0];

        if( direction == 'S' || direction == 'W' )
            dd *= -1;

        directions[ directions.length ] = direction;

        coords[ coords.length ] = dd;
        dd = pow = 0;

    } else {

        dd += ( parseFloat(parts[i]) / Math.pow( 60, pow++ ) );

    }

}

if( directions[0] == 'W' || directions[0] == 'E' ) {
    var tmp = coords[0];
    coords[0] = coords[1];
    coords[1] = tmp;
}

return coords;

}

This function doesn't handle all types of lat / long types, but it handles the following formats:

-31,2222,21.99999
-31 13 13 13.75S, -31 13 13 13.75W
-31 13 13 13.75S -31 13 13 13.75W
-31 13 13 13.75W -31 13.75S
36°57'9" N 110°4'21" W
110°4'21" W 36°57'9"N

Which is what i needed.

Answer 5

I got some NaN's on this function and needed to do this (don't ask me why)

function ConvertDMSToDD(days, minutes, seconds, direction) {
    var dd = days + (minutes/60) + seconds/(60*60);
    dd = parseFloat(dd);
    if (direction == "S" || direction == "W") {
        dd *= -1;
    } // Don't do anything for N or E
    return dd;
}

Answer 6

I used \d+(\,\d+) and \d+(.\d+) because can have float numbers

My final function:

 convertDMSToDD: function (dms) {
     let parts = dms.split(/[^\d+(\,\d+)\d+(\.\d+)?\w]+/);
     let degrees = parseFloat(parts[0]);
     let minutes = parseFloat(parts[1]);
     let seconds = parseFloat(parts[2].replace(',','.'));
     let direction = parts[3];

     console.log('degrees: '+degrees)
     console.log('minutes: '+minutes)
     console.log('seconds: '+seconds)
     console.log('direction: '+direction)

     let dd = degrees + minutes / 60 + seconds / (60 * 60);

     if (direction == 'S' || direction == 'W') {
       dd = dd * -1;
     } // Don't do anything for N or E
     return dd;
   }

Answer 7

Joe, the script you've mentioned already did what do you want. With it you can convert lat and long and put it into link to see location in Google map:

var url = "http://maps.google.com/maps?f=q&source=s_q&q=&vps=3&jsv=166d&sll=" + lat.parseDeg() + "," + longt.parseDeg()

Answer 8

Using Shannon Antonio Black's regex pattern (above), my solution is:

function convertLatLong(input) {

if(!( input.toUpperCase() != input.toLowerCase()) ) {   // if geodirection abbr. isn't exist, it should be already decimal notation
    return `${input}:the coordinate already seems as decimal`
}
const parts = input.split(/[°'"]+/).join(' ').split(/[^\w\S]+/); // thanks to Shannon Antonio Black for regEx patterns 
const geoLetters = parts.filter(el=> !(+el) ) 
const coordNumber = parts.filter(n=>(+n)).map(nr=>+nr)
const latNumber = coordNumber.slice(0,(coordNumber.length/2))
const longNumber = coordNumber.slice((coordNumber.length/2))
const reducer = function(acc,coord,curInd){
   return acc + (coord/Math.pow( 60, curInd++ ))
}
let latDec = latNumber.reduce(reducer)
let longDec = longNumber.reduce(reducer)

if(geoLetters[0].toUpperCase()==='S') latDec = -latDec // if the geodirection is S or W, decimal notation should start with minus
if(geoLetters[1].toUpperCase()==='W') longDec= -longDec 

const dec= [{
    ltCoord: latDec,
    geoLet:geoLetters[0]
},
{
    longCoord: longDec,
    geoLet: geoLetters[1]
}]

return dec
}

I think that is more simplified version with EC6

Answer 9

function convertRawCoordinatesIntoDecimal(input) {
    let grade = parseInt(input.substring(0, input.indexOf("°")));
    let rest = input.substring(input.indexOf("°") + 1);
    let minutes = parseInt(rest.substring(0, rest.indexOf("'")));
    let seconds = parseInt(rest.substring(rest.indexOf("'") + 1).split('"')[0]);
    return grade + (minutes + seconds / 60) / 60;
}

function getCoordinates(input) {
    let parts = input.split(" "); //element 0 is N and element 2 is W coordinates
    return {
        [parts[1]]: convertRawCoordinatesIntoDecimal(parts[0]),
        [parts[3]]: convertRawCoordinatesIntoDecimal(parts[2])
    };
}

let input = `36°57'9" N 110°4'21" W`; //a test input
console.log(getCoordinates(input));

Result:

{
  "N": 36.9525,
  "W": 110.0725
}

Explanation:

• we split by " ", getting an array of strings of four elements
• element 1 will be the name of the first coordinate and element 3 will be the name of the second coordinate
• element 0 will be the value of the first coordinate and element 2 will be the value of the second coordinate
• we dissect the elements into grade, minutes and seconds respectively, all numerical values
• the formula is grade + (minutes + seconds / 60) / 60