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Last active November 7, 2016 21:23
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Rotating Transverse
license: gpl-3.0

A rotating Cassini projection (transverse equirectangular) on the left; a rotating transverse Mercator projection on the right.

<!DOCTYPE html>
<meta charset="utf-8">
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>
var width = 960,
height = 580,
velocity = .003,
time = Date.now();
var position = d3.scale.ordinal()
.domain([0, 1])
.rangePoints([0, width * .87], .8);
var projections = [
d3.geo.equirectangular()
.scale(85)
.translate([position(0), height / 2])
.precision(.3),
d3.geo.mercator()
.scale(85)
.translate([position(1), height / 2])
.precision(.3)
];
var sphere = {type: "Sphere"},
graticule = d3.geo.graticule()();
var canvas = d3.select("body").append("canvas")
.attr("width", width)
.attr("height", height);
var context = canvas.node().getContext("2d");
context.strokeStyle = "#aaa";
var path = d3.geo.path()
.context(context);
d3.json("/mbostock/raw/4090846/world-110m.json", function(error, world) {
if (error) throw error;
var land = topojson.feature(world, world.objects.land);
d3.timer(function() {
var dt = Date.now() - time;
projections[0].rotate([velocity * dt, 0, 90]);
projections[1].rotate([velocity * dt, 0, 90]);
render();
});
function render() {
context.clearRect(0, 0, width, height);
projections.forEach(function(projection) {
var translate = projection.translate();
context.save();
context.translate(translate[0], translate[1]);
context.rotate(Math.PI / 2);
context.translate(-translate[0], -translate[1]);
path.projection(projection);
context.beginPath();
path(sphere);
context.stroke();
context.beginPath();
path(graticule);
context.stroke();
context.beginPath();
path(land);
context.fill();
context.restore();
});
}
});
d3.select(self.frameElement).style("height", height + "px");
</script>
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