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GeoEllipse
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <body> | |
| <script src="https://d3js.org/d3.v4.min.js"></script> | |
| <script src="https://d3js.org/topojson.v1.min.js"></script> | |
| <script> | |
| var width = 800; | |
| var height = 800; | |
| var svg = d3.select("body").append("svg") | |
| .attr("width",width) | |
| .attr("height",height); | |
| var projection = d3.geoOrthographic(); | |
| var path = d3.geoPath().projection(projection); | |
| d3.json("https://unpkg.com/world-atlas@1/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); | |
| var ellipses = [[1000000,500000,50,70,45],[100000,500000,-50,70],[1000000,3000000],[3000000,1000000,-100,-20],[1000000,3000000,100,-20,15]] | |
| var geojson = ellipses.map(function(d) { | |
| return createEllipse(...d); | |
| }) | |
| svg.selectAll() | |
| .data(geojson) | |
| .enter() | |
| .append("path") | |
| .attr("d",path) | |
| .attr("fill","orange"); | |
| var speed = 0.5e-2; | |
| var start = Date.now(); | |
| d3.timer(function() { | |
| projection.rotate([speed * (Date.now() - start), -15]); | |
| d3.selectAll("path").attr("d",path); | |
| }); | |
| }) | |
| function createEllipse(a,b,x,y,rotation) { | |
| if(typeof rotation == 'undefined') { rotation = 0; } | |
| if(typeof x == 'undefined') { x = 0; } | |
| if(typeof y == 'undefined') { y = 0; } | |
| var k = Math.ceil(36 * (Math.max(a/b,b/a))); // sample angles | |
| var coords = []; | |
| for (var i = 0; i <= k; i++) { | |
| // get the current angle | |
| var angle = Math.PI*2 / k * i + rotation | |
| // get the radius at that angle | |
| var r = a * b / Math.sqrt(a*a*Math.sin(angle)*Math.sin(angle) + b*b*Math.cos(angle)*Math.cos(angle)); | |
| coords.push(getLatLong([x,y],angle,r)); | |
| } | |
| return { "type":"Polygon", "coordinates":[coords] }; | |
| } | |
| function getLatLong(center,angle,radius) { | |
| var rEarth = 6371000; // meters | |
| x0 = center[0] * Math.PI / 180; // convert to radians. | |
| y0 = center[1] * Math.PI / 180; | |
| var y1 = Math.asin( Math.sin(y0)*Math.cos(radius/rEarth) + Math.cos(y0)*Math.sin(radius/rEarth)*Math.cos(angle) ); | |
| var x1 = x0 + Math.atan2(Math.sin(angle)*Math.sin(radius/rEarth)*Math.cos(y0), Math.cos(radius/rEarth)-Math.sin(y0)*Math.sin(y1)); | |
| y1 = y1 * 180 / Math.PI; | |
| x1 = x1 * 180 / Math.PI; | |
| return [x1,y1]; | |
| } | |
| </script> |
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