Hi,
I am working on an enhancement to the map accessible at http://travellr.com/map
The idea is to be able to load the map on a country, and have the map
zoomed to appropriately fit the country. For all countries I have co-
ordinates and bounding boxes already.
The problem is that when using Map.fitBounds(), the zoom level
sometimes isn't quite right - for loading on countries I would like to
limit zoom within a min / max, and places like Russia and Canada
break out of that. After using Map.fitBounds(), I could then check the
zoom level once the zoom_changed event fires, and if required update
it, but that seems quite a clunky multi step process.
Ideally I would like to be able to calculate the zoom level prior to
instantiating the map. However the API v3 does not seem to provide a
way to do this.
I have read some solutions akin to:
// mnode = the map node
// bounds = a bounding box
function best_zoom(bounds, mnode) {
var width = mnode.offsetWidth;
var height = mnode.offsetHeight;
var dlat = Math.abs(bounds.maxY - bounds.minY);
var dlon = Math.abs(bounds.maxX - bounds.minX);
// Center latitude in radians
var clat = Math.PI*(bounds.minY + bounds.maxY)/360.;
var C = 0.0000107288;
var z0 = Math.ceil(Math.log(dlat/(C*height))/Math.LN2);
var z1 = Math.ceil(Math.log(dlon/(C*width*Math.cos(clat)))/
Math.LN2);
return (z1 > z0) ? z1 : z0;
}
However this does not seem to provide the correct zoom levels (they
increase as dlat or dlon increase, shouldn't they go down?) - Please
tell me if I am missing something here? Also, where does the constant
C come from?
Thanks for your help.
- Jai
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