This is actually a nasty problem when the objects that you are trying
to fit are large. For V2 I used:
function zoomRecenter(map, bounds) {
map.setZoom(map.getBoundsZoomLevel(bounds));
map.panTo(bounds.getCenterMap(map));
}
GLatLngBounds.prototype.getCenterMap = function(m) {
var p = m.getCurrentMapType().getProjection();
var b = new GBounds;
b.extend(p.fromLatLngToPixel(this.getNorthEast(), m.getZoom()));
b.extend(p.fromLatLngToPixel(this.getSouthWest(), m.getZoom()));
return new GLatLng(p.fromPixelToLatLng(b.mid(),
m.getZoom()).lat(), this.getCenter().lng());
}
Note the complexity of finding the *pixel* middle of a GBounds.
However, since it isn't possible (currently) in V3 to get the
projection in use by the current basemap, you are somewhat hosed.
You can star the bug at
http://code.google.com/p/gmaps-api-issues/issues/detail?id=2181&q=apitype%3AJavascript3%20type%3ADefect&sort=-id%20-stars&colspec=ID%20Type%20Status%20Introduced%20Fixed%20Summary%20Internal%20Stars
if you want.
Philip
On Feb 16, 12:58 am, Jaidev S <[email protected]> wrote:
> Hi,
>
> I am working on an enhancement to the map accessible athttp://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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