[ka-Map-users] Re: ka-Map-users Digest, Vol 10, Issue 15

[Ricardo Stuven]

On 2/16/06, Moran Ben-David <moran at placebase.com> wrote:
> I suggest you do what mapbuilder developers had to do...
> Which is to rip open proj4 (http://proj.maptools.org/) and lookup the
> projection calculation you are looking for in there.
> The file you want should have look like PJ_<your projection>.c.  Keep in
> mind that inside that file, the coordinates are all in radians and not
> decimal degrees.

Thank you, but let me be more specific. I have already seen several
different methods to make this conversion. The question is which is
the more appropiate one to use within ka-map and where do I get the
ka-map parameters I need to do feed the conversion...

For example, I already know how to calculate the extent in equidistant
coordinates using ka-map's variables cellSize, xOrigin, yOrigin and
tile position:

    var minEX = km.cellSize * (safeParseInt(img.style.left) + km.xOrigin);
    var minEY = -1*km.cellSize * (safeParseInt(img.style.top) + km.yOrigin);
    var maxEX = minX + km.cellSize * km.tileWidth;
    var maxEY = minY - km.cellSize * km.tileHeight;

What remains I think it's as simple as the conversion from pixel to
equidistant (because AFAIK it's linear too) but I'm lost on how to
exactly get it with ka-map (e.g. something like var minGX = minEX *
factorX;).

Thanks,
Ricardo Stuven.