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@mbostock mbostock/.block
Last active Feb 9, 2016

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Two Point Equidistant
license: gpl-3.0

This is still a work in progress; elliptical clipping is needed to avoid visible artifacts outside of 145° in this example.

<!DOCTYPE html>
<meta charset="utf-8">
<style>
.background {
fill: #ff0;
fill-opacity: .1;
}
.foreground {
fill: none;
stroke: #333;
stroke-width: 1.5px;
}
.graticule {
fill: none;
stroke: #f00;
stroke-width: .5px;
}
.land {
fill: cyan;
fill-opacity: .5;
}
</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/d3.geo.projection.v0.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>
var width = 960,
height = 652;
var a = [-158, 21.5], // Honolulu, HI
b = [-77, 39]; // Washington, DC
var projection = d3.geo.twoPointEquidistant()
.points([a, b])
.scale(132.5)
.translate([width / 2, height / 2])
.clipAngle(145) // TODO clip to ellipse
.precision(.1);
var path = d3.geo.path()
.projection(projection);
var graticule = d3.geo.graticule()
.minorStep([15, 15])
.minorExtent([[-180, -75], [180, 75 + 1e-4]]);
var svg = d3.select("body").append("svg")
.attr("width", width)
.attr("height", height);
svg.append("image")
.attr("xlink:href", "two-point-equidistant.png")
.attr("transform", "rotate(1.2 " + width / 2 + "," + height / 2 + ")")
.attr("width", width)
.attr("height", height);
svg.append("defs").append("path")
.datum({type: "Sphere"})
.attr("id", "sphere")
.attr("d", path);
svg.append("use")
.attr("class", "background")
.attr("xlink:href", "#sphere");
svg.append("path")
.datum(graticule)
.attr("class", "graticule")
.attr("d", path);
d3.json("/mbostock/raw/4090846/world-50m.json", function(error, world) {
if (error) throw error;
svg.insert("path", ".graticule")
.datum(topojson.feature(world, world.objects.land))
.attr("class", "land")
.attr("d", path);
});
d3.select(self.frameElement).style("height", height + "px");
</script>
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