converting UTM - Decimal Degrees with javaScript or using a web service

Question

I am creating a wildlife survey form that has a field where users enter location. Users will be able to enter location using a map (i.e. draggable pushpin) or by manually entering lat/lng. My clients are also requesting an option for entering UTM coordinates.

If a user does enter UTM coords I would like to convert these before pushing to the database. I've seen a couple websites that have utilities for converting UTM to decimal degrees.

Does anyone know of a javaScript lib that will make these conversion given zone and easting-northing? I also saw this thread

Convert geographic coordinates to UTM zone 29N with Javascript

Does ESRI have a web service that I could pass UTM coords to and get lat/lng back?

Answer 1

If you're not happy with using a Geometry Service like Kirk suggested, you could use proj4js client-side.

Answer 2

You could use the GeometryService on sampleserver6, but there's no guarantee Esri won't change or remove it.

Can call it using javascript Project method.

Answer 3

I used this code to convert wgs84 to utm and utm to wgs84. Caution: Accuracy of this code is about one meter.

<script>
function Wgs2Utm( lan1,fi) {

var a=6378137.000;
var b=6356752.314;
var f=(a-b)/a;
var e2=Math.sqrt((Math.pow(a,2)-Math.pow(b,2))/Math.pow(b,2));
var e=Math.sqrt((Math.pow(a,2)-Math.pow(b,2))/Math.pow(a,2));

var zone;
var lan0;
if (lan1>0)
{
    var zone=30+Math.ceil(lan1/6);
    lan0=Math.floor(lan1/6)*6+3;
}
else
{
    var zone=30-Math.floor(Math.abs(lan1)/6);
    lan0=-Math.floor(Math.abs(lan1)/6)*6-3;
}


//-----------------------------------------------

var lan=lan1-lan0;
lan=lan*Math.PI/180;
fi=fi*Math.PI/180;
var N=a/Math.pow(1-Math.pow(e,2)*Math.pow(Math.sin(fi),2),0.5);
var M=a*(1-Math.pow(e,2))/Math.pow((1-(Math.pow(e,2)*Math.pow(Math.sin(fi),2))),(3/2));
var t=Math.tan(fi);
var p=N/M;

//----------------------------------------------
var k0=0.9996;

var term1=Math.pow(lan,2)*p*Math.pow(Math.cos(fi),2)/2;
var term2=Math.pow(lan,4)*Math.pow(Math.cos(fi),4)*(4*Math.pow(p,3)*(1-6*Math.pow(t,2))+Math.pow(p,2)*(1+24*Math.pow(t,2))-4*p*Math.pow(t,2))/24;
var term3=Math.pow(lan,6)*Math.pow(Math.cos(fi),6)*(61-148*Math.pow(t,2)+16*Math.pow(t,4))/720;

var Kutm=k0*(term1+term2+term3);


//----------------------------------------------
term1=Math.pow(lan,2)*p*Math.pow(Math.cos(fi),2)*(p-Math.pow(t,2))/6;
term2=Math.pow(lan,4)*Math.pow(Math.cos(fi),4)*(4*Math.pow(p,3)*(1-6*Math.pow(t,2))+Math.pow(p,2)*(1+8*Math.pow(t,2))-Math.pow(p,2)*Math.pow(t,2)+Math.pow(t,4))/120;
term3=Math.pow(lan,6)*Math.pow(Math.cos(fi),6)*(61-479*Math.pow(t,2)+179*Math.pow(t,4)-Math.pow(t,6))/5040;

var Xutm=500000+k0*lan*N*Math.cos(fi)*(1+term1+term2+term3);

//----------------------------------------------

var A0=1-0.25*Math.pow(e,2)-3/64*Math.pow(e,4)-5/256*Math.pow(e,6);
var A2=3/8*(Math.pow(e,2)+0.25*Math.pow(e,4)+15/128*Math.pow(e,6));
var A4=15/256*(Math.pow(e,4)+0.75*Math.pow(e,6));
var A6=35/3072*Math.pow(e,6);

var sfi=a*(A0*fi-A2*Math.sin(2*fi)+A4*Math.sin(4*fi)-A6*Math.sin(6*fi));

//----------------------------------------------

term1=Math.pow(lan,2)*N*Math.sin(fi)*Math.cos(fi)/2;
term2=Math.pow(lan,4)*N*Math.sin(fi)*Math.pow(Math.cos(fi),3)*(4*Math.pow(p,2)+p-Math.pow(t,2))/24;
term3=Math.pow(lan,6)*N*Math.sin(fi)*Math.pow(Math.cos(fi),5)*(8*Math.pow(p,4)*(11-24*Math.pow(t,2))-28*Math.pow(p,3)*(1-6*Math.pow(t,2))+Math.pow(p,2)*(1-32*Math.pow(t,2))-p*2*Math.pow(t,2)+Math.pow(t,4));
var term4=Math.pow(lan,8)*N*Math.sin(fi)*Math.pow(Math.cos(fi),7)*(1385-3111*Math.pow(t,2)+543*Math.pow(t,4)-Math.pow(t,6));

var Yutm=k0*(sfi+term1+term2+term3+term4);
var sn='N';
if (fi <0)
{
    Yutm = 10000000 + Yutm;
    sn='S';
}
    return Xutm.toString().concat(" ; " + Yutm.toString() + " "+zone.toString()+sn) ;

}

function Utm2Wgs( X,Y,zone,sn) {
    if (sn=='S')
    {
        Y = Y - 10000000;
    }
    X = X - 500000;
    var sa = 6378137.000000;
    var sb = 6356752.314245;

   var e = Math.pow( Math.pow(sa , 2) - Math.pow(sb , 2) , 0.5 ) / sa;
   var e2 = Math.pow( Math.pow( sa , 2 ) - Math.pow( sb , 2 ) , 0.5 ) / sb;
   var e2cuadrada = Math.pow(e2 , 2);
   var c = Math.pow(sa , 2 ) / sb;



   var S = ( ( zone * 6 ) - 183 ); 
   var lat =  Y / ( 6366197.724 * 0.9996 );                         
   var v =  (c * 0.9996)/ Math.pow( 1 + ( e2cuadrada * Math.pow( Math.cos(lat), 2 ))  , 0.5 ) ;
   var a = X / v;
   var a1 = Math.sin( 2 * lat );
   var a2 = a1 * Math.pow( Math.cos(lat), 2);
   var j2 = lat + ( a1 / 2 );
   var j4 = ( ( 3 * j2 ) + a2 ) / 4;
   var j6 = ( ( 5 * j4 ) + ( a2 * Math.pow( Math.cos(lat) , 2) ) ) / 3;
   var alfa = ( 3 / 4 ) * e2cuadrada;
   var beta = ( 5 / 3 ) * Math.pow(alfa , 2);
   var gama = ( 35 / 27 ) * Math.pow(alfa , 3);
   var Bm = 0.9996 * c * ( lat - alfa * j2 + beta * j4 - gama * j6 );
   var b = ( Y - Bm ) / v;
   var Epsi = ( ( e2cuadrada * Math.pow(a , 2)) / 2 ) * Math.pow( Math.cos(lat) , 2);
   var Eps = a * ( 1 - ( Epsi / 3 ) );
   var nab = ( b * ( 1 - Epsi ) ) + lat;
   var senoheps = ( Math.exp(Eps) - Math.exp(-Eps) ) / 2;
   var Delt = Math.atan(senoheps / Math.cos(nab) );
   var TaO = Math.atan(Math.cos(Delt) * Math.tan(nab));
   var longitude = (Delt *(180 / Math.PI ) ) + S;
   var latitude = ( lat + ( 1 + e2cuadrada* Math.pow(Math.cos(lat), 2) - ( 3 / 2 ) * e2cuadrada * Math.sin(lat) * Math.cos(lat) * ( TaO - lat ) ) * ( TaO - lat ) ) * (180 / Math.PI);
    return longitude.toString().concat(" ; " + latitude.toString()) ;
}

</script>