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Bottomley projection
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license: mit |
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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; |
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<!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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