D3.js geoWinkel3() Function

Last Updated : 30 Aug, 2021

D3.js is a JavaScript library for producing dynamic, interactive data visualizations in web browsers. It makes use of Scalable Vector Graphics, HTML5, and Cascading Style Sheets standards.

The geoWinkel3() function in d3.js is used to draw the Winkel triple projection which is a compromise modified azimuthal projection for world maps. It is an arithmetic mean of projected coordinates of Aitoff and equidistant cylindrical projections. The projection is known to have one of the lowest mean scale and area distortions among compromise projections for small-scale mapping.

Syntax:

d3.geoWinkel3()

Parameters: This method does not accept any parameters.

Return Value: This method creates and returns the Winkel3 projection from the given JSON data.

Example 1: The following example makes the Winkel3 projection of world with center at (0,0) and 0 rotation.

HTML

<!DOCTYPE html> 
<html lang="en"> 
 
<head> 
    <meta charset="UTF-8" /> 
    <meta name="viewport"
        content="width=device-width, 
                initial-scale=1.0"/> 
 
    <script src="https://d3js.org/d3.v4.js"></script>
 
    <script src=
"https://d3js.org/d3-geo-projection.v2.min.js">
    </script> 
</head> 
 
<body> 
    <div style="width:700px; height:500px;"> 
        <svg width="600" height="450"> 
        </svg> 
    </div> 
     
    <script>
        var svg = d3.select("svg"),
            width = +svg.attr("width"),
            height = +svg.attr("height");
 
        // Winkel3 projection
        // Center(0,0) with 0 rotation
        var gfg = d3.geoWinkel3()
            .scale(width / 1.5 / Math.PI)
            .rotate([0,0])
            .center([0,0])
            .translate([width / 2, height / 2])
 
        // Loading the json data
        d3.json(
            "https://raw.githubusercontent.com/"
            +"janasayantan/datageojson/master/world.json", 
            function(data){
                // Draw the map
                svg.append("g")
                    .selectAll("path")
                    .data(data.features)
                    .enter().append("path")
                    .attr("fill", "SlateBlue")
                    .attr("d", d3.geoPath()
                        .projection(gfg)
                    )
                    .style("stroke", "#ffff")
        });
    </script>
</body> 
 
</html>

Output:

Winkel3 projection of World with no rotation and centered at (0,0)

Example 2: The following example makes Winkel3 projection of world after customizing the center and rotation

HTML

<!DOCTYPE html> 
<html lang="en"> 
 
<head> 
    <meta charset="UTF-8" /> 
    <meta name="viewport"
        content="width=device-width, 
                initial-scale=1.0"/> 
 
    <script src="https://d3js.org/d3.v4.js"></script>
 
    <script src=
"https://d3js.org/d3-geo-projection.v2.min.js">
    </script>
</head> 
 
<body> 
    <div style="width:500px; height:600px;"> 
        <svg width="500" height="450"> 
        </svg> 
    </div> 
     
    <script>
        var svg = d3.select("svg"),
            width = +svg.attr("width"),
            height = +svg.attr("height");
 
        // Winkel3  projection
        // Center(-10,0) and -90 degree
        // rotation w.r.t Y axis
        var gfg = d3.geoWinkel3()
            .scale(width / 1.3 / Math.PI)
            .rotate([-90,0])
            .center([-10,0])
            .translate([width / 2, height / 2]);
 
        // Loading the json data
        d3.json(
            "https://raw.githubusercontent.com/"
            +"janasayantan/datageojson/master/world.json", 
            function(data){
                // Draw the map
                svg.append("g")
                    .selectAll("path")
                    .data(data.features)
                    .enter().append("path")
                    .attr("fill", "SaddleBrown")
                    .attr("d", d3.geoPath()
                        .projection(gfg)
                    )
                    .style("stroke", "#ffff")
        })
    </script>
</body> 
 
</html>