D3.js geoHealpix() Function
Last Updated :
30 Sep, 2020
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
+"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
+"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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