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Last active April 30, 2017 13:47
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Bottomley projection
license: mit
var π = Math.PI, halfπ=π/2;
function bottomleyRaw(ψ) {
function forward(λ, φ) {
var ρ = halfπ - φ,
η = ρ ? λ * Math.sin(ψ) * Math.sin(ρ) / ρ : ρ;
return [
ρ * Math.sin(η) / Math.sin(ψ),
halfπ - ρ * Math.cos(η)
];
}
forward.invert = function(x, y) {
var x1 = x * Math.sin(ψ),
y1 = halfπ - y;
var ρ = Math.sqrt( x1 * x1 + y1 * y1 ),
η = Math.atan( x1 / y1 );
return [
(ρ ? ρ / Math.sin(ρ) : 1) * η / Math.sin(ψ),
halfπ - ρ
];
};
return forward;
}
(d3.geo.bottomley = function() {
var ψ = π/6,
mutate = d3.geo.projectionMutator(bottomleyRaw),
projection = mutate(ψ);
projection.variant = function(_) {
if (!arguments.length) return ψ;
return mutate(ψ = _);
};
return projection;
}).raw = bottomleyRaw;
<!DOCTYPE html>
<meta charset="utf-8">
<style>
body {
background: #fcfcfa;
}
.stroke {
fill: none;
stroke: #000;
stroke-width: 3px;
}
.fill {
fill: #fff;
}
.graticule {
fill: none;
stroke: #777;
stroke-width: .5px;
stroke-opacity: .5;
}
.land {
fill: #222;
}
.boundary {
fill: none;
stroke: #fff;
stroke-width: .5px;
}
</style>
<body>
<script src="//d3js.org/d3.v4.min.js"></script>
<script src="//d3js.org/d3-geo-projection.v2.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>
var width = 960,
height = 500;
var projection = d3.geoBottomley()
.scale(155)
.translate([width / 2, height / 2])
.precision(.1);
var path = d3.geoPath()
.projection(projection);
var graticule = d3.geoGraticule();
var svg = d3.select("body").append("svg")
.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", "stroke")
.attr("xlink:href", "#sphere");
svg.append("use")
.attr("class", "fill")
.attr("xlink:href", "#sphere");
svg.append("path")
.datum(graticule)
.attr("class", "graticule")
.attr("d", path);
d3.json("https://gist.githubusercontent.com/mbostock/4090846/raw/d534aba169207548a8a3d670c9c2cc719ff05c47/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);
svg.insert("path", ".graticule")
.datum(topojson.mesh(world, world.objects.countries, function(a, b) { return a !== b; }))
.attr("class", "boundary")
.attr("d", path);
});
</script>
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