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Began code for feature lookup: implemented code to respond to mouse click and latlon to non spherical Mercator (for the postgis database)

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Nick Whitelegg 2008-01-07 20:25:12 +00:00
parent f29300bf1a
commit 2e03861300
4 changed files with 62 additions and 3 deletions
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50
public/javascripts/map.js
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@ -146,6 +146,56 @@ function lonLatToMercator(ll) {
return new OpenLayers.LonLat(lon, lat);
}
// for interacting with the PostGIS database which uses non spherical
// Mercator. Taken from Freemap which in turn was taken from a standard
// algorithm off the net.
function lonLatToNonSphericalMercator(ll) {
var custLat = ll.lat * (Math.PI/180);
var a = 6378137;
var b = 6356752.3142;
var f = (a-b)/a;
var e = Math.sqrt(2*f-Math.pow(f,2));
custLat=a*Math.log(Math.tan(Math.PI/4+custLat/2)*
Math.pow(( (1-e*Math.sin(custLat)) / (1+e*Math.sin(custLat))),e/2));
custLon = ll.lon * (Math.PI/180) * 6378137;
return new OpenLayers.LonLat (custLon,custLat);
}
function nonSphericalMercatorToLonLat(merc) {
var lon_deg, lat_deg;
var a = 6378137.0;
var b = 6356752.3142;
var k0 = 1.0;
var t = 1.0 - b/a;
var es = 2*t - t*t;
var e = Math.sqrt(es);
lon_deg = merc.lon;
lat_deg = merc.lat;
lon_deg /= a;
lat_deg /= a;
lon_deg /= k0;
lat_deg = phi2(Math.exp(-lat_deg/k0), e);
lon_deg *= (180/M_PI);
lat_deg *= (180/M_PI);
return new OpenLayers.LonLat(lon_deg,lat_deg);
}
function phi2 (ts,e) {
var eccnth = 0.5*e;
var Phi = (PI/2) - 2.0*Math.atan(ts);
var dphi;
var i=15;
do {
var con = e*Math.sin(Phi);
dphi = (PI/2) - 2.0*Math.atan(ts*Math.pow((1.0-con)/(1.0+con),eccnth))
- Phi;
Phi += dphi;
}
while(Math.abs(dphi) > 0.0000000001 && --i);
return Phi;
}
function scaleToZoom(scale) {
return Math.log(360.0/(scale * 512.0)) / Math.log(2.0);
}