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Add more explanations to xyz-esri-4326-512 example

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This commit is contained in:
Éric Lemoine
2014-10-09 13:20:51 +02:00
parent c1259aacab
commit c69974f460
1 changed files with 11 additions and 3 deletions
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14
examples/xyz-esri-4326-512.js
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@@ -14,10 +14,18 @@ var attribution = new ol.Attribution({
var projection = ol.proj.get('EPSG:4326');
var projectionExtent = projection.getExtent();
var size = ol.extent.getWidth(projectionExtent) / 256;
// The tile size supported by the ArcGIS tile service.
var tileSize = 512;
// Calculate the resolutions supported by the ArcGIS tile service.
// There are 16 resolutions, with a factor of 2 between successive
// resolutions. The max resolution is such that the world (360°)
// fits into two (512x512 px) tiles.
var maxResolution = ol.extent.getWidth(projectionExtent) / (tileSize * 2);
var resolutions = new Array(16);
for (var z = 2; z < 18; ++z) {
resolutions[z - 2] = size / Math.pow(2, z);
var z;
for (z = 0; z < 16; ++z) {
resolutions[z] = maxResolution / Math.pow(2, z);
}
var url = 'http://services.arcgisonline.com/arcgis/rest/services/' +