Calculate the mid point of latitude and longitude co-ordinates

Question

Does anyone know the best way to go about getting the mid-point of a pair of latitude and longitude points?

I mm using d3.js to draw points on a map and need to draw

Answer 1

Check this question, you can use it to find the middle of your coordination on google map. I customized it to use with d3js. Hope this help you.

In D3

function midpoint (lat1, lng1, lat2, lng2) {

lat1= deg2rad(lat1);
lng1= deg2rad(lng1);
lat2= deg2rad(lat2);
lng2= deg2rad(lng2);

dlng = lng2 - lng1;
Bx = Math.cos(lat2) * Math.cos(dlng);
By = Math.cos(lat2) * Math.sin(dlng);
lat3 = Math.atan2( Math.sin(lat1)+Math.sin(lat2),
Math.sqrt((Math.cos(lat1)+Bx)*(Math.cos(lat1)+Bx) + By*By ));
lng3 = lng1 + Math.atan2(By, (Math.cos(lat1) + Bx));

   return (lat3*180)/Math.PI .' '. (lng3*180)/Math.PI;
}

function deg2rad (degrees) {
    return degrees * Math.PI / 180;
};

Update 1

If you try to draw curve line, you should create a path with coordination such as :

var lat1=53.507651,lng1=10.046997,lat2=52.234528,lng2=10.695190;


    var svg=d3.select("body").append("svg").attr({width:700 , height:600});
    svg.append("path").attr("d", function (d) {
      var dC="M "+lat1+","+lng1+ " A " + midpoint (lat1, lng1, lat2, lng2)
         + " 0 1,0 " +lat2 +" , "+lng2 +"Z";
        return dC;

    })
    .style("fill","none").style("stroke" ,"steelblue");

You need to create your curve line as you want in d3. JsFiddle here.