D3.js geoGnomonic() Function

Last Updated : 15 Oct, 2020

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 geoGnomonic() function in d3.js is used to draw the gnomonic projection which is an azimuthal projection that projects great circles as straight lines, regardless of the aspect.

Syntax:

d3.geoGnomonic()

Parameters: This method does not accept any parameters.

Return Value: This method creates a gnomonic projection from given JSON data.

Example 1: The following example makes a gnomonic projection of the world with the center at (0,0) and no 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;">  
        <center>  
            <h3 style="color:black"></h3>  
        </center>  
        <svg width="600" height="450">  
        </svg>  
    </div>  
  
    <script>  
        var svg = d3.select("svg"),  
        width = +svg.attr("width"),  
        height = +svg.attr("height");  
  
        // Gnomonic projection  
        // Center(0,0) with 0 rotation  
        var gfg = d3.geoGnomonic()  
                    .scale(width / 1.8 / 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){  
                // Drawing the map  
                svg.append("g")  
                    .selectAll("path")  
                    .data(data.features)  
                    .enter().append("path")  
                    .attr("fill", "black")  
                    .attr("d", d3.geoPath()  
                        .projection(gfg)  
                    )  
                    .style("stroke", "#ffff")  
                }); 
    </script>  
</body>  
    
</html>

Output:

Gnomonic conic projection with no rotation and centered at (0,0)

Example 2: The following example makes a gnomonic projection of the world after customizing the center(-20,-20) and rotating -90 degree w.r.t Y-axis.

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;">  
        <center>  
            <h3 style="color:black"></h3>  
        </center>  
        <svg width="600" height="450">  
        </svg>  
    </div>  
  
    <script>  
        var svg = d3.select("svg"),  
        width = +svg.attr("width"),  
        height = +svg.attr("height");  
  
        // Gnomonic  projection   
        // Center(-20,-20) and -90 degree  
        // rotation w.r.t Y axis   
        var gfg = d3.geoGnomonic()  
                    .scale(width / 1.3 / Math.PI)  
                    .rotate([0,-90])  
                    .center([-20,-20])  
                    .translate([width / 2, height / 2]); 
  
        // Loading the json data  
        d3.json("https://raw.githubusercontent.com/"  
            + "janasayantan/datageojson/master/world.json",  
            function(data){  
  
                // Drawing the map  
                svg.append("g")  
                    .selectAll("path")  
                    .data(data.features)  
                    .enter().append("path")  
                    .attr("fill", "slategrey")  
                    .attr("d", d3.geoPath()  
                        .projection(gfg)  
                    )  
                    .style("stroke", "#ffff")  
                }); 
    </script>  
</body>  
  
</html>