The d3.geoHealpix() function returns Hierarchical Equal Area isoLatitude Pixelization of a 2-sphere. In this implementation, the parameter K is fixed at 3.
Note: It requires clipping to the sphere.
Syntax:
d3.geoHealpix()
Parameters: This method does not accept any parameter.
Return Value: This method creates Healpix projection from the given JSON data.
Example 1: The following example creates Healpix projection of the world with 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> <script src= </script> </head> <body> <div style="width:700px; height:600px;"> <svg width="700" height="550"> </svg> </div> <script> var svg = d3.select("svg"), width = +svg.attr("width"), height = +svg.attr("height"); // Healpix projection // Center(0, 0) and no rotation var gfg = d3.geoHealpix() .scale(width / 1.5 / Math.PI) .rotate([0, 0]) .center([0, 0]) .translate([width / 2, height / 3]) // Loading the json data // Used json file stored at // GeoLocation/master/world.json d3.json("https://raw.githubusercontent.com/" +"epistler999/GeoLocation/master/world.json", function (data) { // Draw 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> </html> |
Output:
Example 2 : In the following example we will create HealPix projection of world with center at (30, 0) and rotating 30 degree anti-clockwise with respect to 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> <script src= </script> </head> <body> <div style="width:700px; height:600px;"> <svg width="700" height="550"> </svg> </div> <script> var svg = d3.select("svg"), width = +svg.attr("width"), height = +svg.attr("height"); // Healpix projection // Center(30, 0) and 30 degree rotation var gfg = d3.geoHealpix() .scale(width / 1.5 / Math.PI) .rotate([-30, 0]) .center([30, 0]) .translate([width / 2, height / 2]) // Loading the json data // Used json file stored at // GeoLocation/master/world.json d3.json("https://raw.githubusercontent.com/" +"epistler999/GeoLocation/master/world.json", function (data) { // Draw 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 :
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