I have something close I think.
My function returns the coordinates that represent a certain tile.
From there what you need is to calculate the exact lat/lng position
within this tile...
It is not exactly what you are asking for and you need to remove some
stuff, but I just had this file open when I read your email :)
---------
private function
getPolygonCoordsFromTileCoords(x:Number,y:Number,zoom:Number):Array {
zoom = 17 - zoom;
var lon:Number = -180; // x
var lonWidth:Number = 360; // width 360
var lat:Number = -1;
var latHeight:Number = 2;
var tilesAtThisZoom:Number = 1 << (17 - zoom);
lonWidth = 360.0 / tilesAtThisZoom;
lon = -180 + (x * lonWidth);
latHeight = -2.0 / tilesAtThisZoom;
lat = 1 + (y * latHeight);
// convert lat and latHeight to degrees in a transverse
mercator projection
// note that in fact the coordinates go from about -85 to
+85
not -90 to 90!
latHeight += lat;
latHeight = (2 * Math.atan(Math.exp(Math.PI *
latHeight))) -
(Math.PI / 2);
latHeight *= (180 / Math.PI);
lat = (2 * Math.atan(Math.exp(Math.PI * lat))) - (Math.PI
/ 2);
lat *= (180 / Math.PI);
latHeight -= lat;
if (lonWidth < 0) {
lon = lon + lonWidth;
lonWidth = -lonWidth;
}
if (latHeight < 0) {
lat = lat + latHeight;
latHeight = -latHeight;
}
return [
new LatLng(lat,lon),
new LatLng(lat+latHeight,lon),
new LatLng(lat+latHeight,lon+lonWidth),
new LatLng(lat,lon+lonWidth),
new LatLng(lat,lon)];
}
-----------
Javier de la Torre
www.vizzuality.com
On Jan 29, 2009, at 12:30 AM, Michael Hansen wrote:
>
> OK, so I have the lat/lng to pixel/tile calcs all worked out. Anyone
> have the reverse worked out before I go re-invent the wheel?
> >
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