[OpenLayers-Dev] Google Zoom Levels

[Erik Uzureau]

ludwig, I will try to take a look at this if I have a spare moment
this weekend... if not I will check it out on monday. I am the one
who wrote most of this code, as well as this wiki which is
supposed to help people figure this out:

http://trac.openlayers.org/wiki/SettingZoomLevels

Let me know if you come to any resolutions, and if not, i'll take
a look ASAP.

regards,
Erik

On 11/17/06, Ludwig Max Brinckmann <ludwigbrinckmann at gmail.com> wrote:
> I was planning to look a bit more into it this afternoon (London
> time), but since people seem to get a bit impatient about it, this is
> the preliminary result:
>
> First, we have to up the zoom levels on in Google.js and add some more
> resolutions:
>
>     /** @final @type int */
>     MAX_ZOOM_LEVEL: 23,
>
>     /** Hardcode these resolutions so that they are more closely
>      *   tied with the standard wms projection
>      *
>      * @final @type Array(float) */
>     RESOLUTIONS: [1.40625,0.703125,0.3515625,0.17578125,0.087890625,0.043945312\
> 5,0.02197265625,0.010986328125,0.0054931640625,0.00274658203125,0.0013732910156\
> 25,0.0006866455078125,0.00034332275390625,0.000171661376953125,0.00008583068847\
> 65625,0.00004291534423828125,0.0000214576721191140625,0.000107288360595703125,0\
> .0000053644182978515625,0.000002682209014892578125,0.0000013411045074462890625,\
> 0.00000067055225372314453125],
>
>
> Then the map needs to be told that to go to a higher maxResolution AND
> that there are more zoomLevels, just one of them won't do (why? - I
> was planning to look a bit more into the code in FixedZoomLevels.js to
> find out).
> var map = new OpenLayers.Map('map', {controls:[], numZoomLevels: 19,
> maxZoomLevel: 19});
>
> In my case, however, I have decided that I actually want to stop
> people zooming out too much so I upped the lower zoom level
>
> var map = new OpenLayers.Map('map', {controls:[], numZoomLevels: 15,
> minZoomLevel: 5, maxZoomLevel: 19});
>
> So far, so good, if not very obvious.
>
> But:
> Now I have the interesting situation that my layerswitcher stops
> working above a certain zoomlevel: the selection boxes just go grey
> and I cannot change the selection anymore (and it seems it does not
> make anything visible beyond the google base layer.)
>
> E.g.
> http://www.yunnanexplorer.com/yunnanmap.html?lat=24.95739&lon=101.91948&zoom=10&layers=BFFFT
> shows the grey boxes, while
> http://www.yunnanexplorer.com/yunnanmap.html?lat=24.95739&lon=101.91948&zoom=8&layers=BFFFT
> enables the layer switcher combo boxes.
>
> Firefox seems to eat any errors while IE throws up an error, in
> WMS.Untiled destroy, where this.tile is not defined (this error might
> be something completely different, it is IE after all).
>
> I will look a bit more into it later today, but if anyone has an idea.
>
> Ludwig
>
>
> Is this a feature? Is there a zoomlevel equivalent in the WMS Layers?
>
> Ludwig
>
>
>
>
>
>
>
>
>
> On 11/16/06, Schuyler Erle <sderle at metacarta.com> wrote:
> > * On 16-Nov-2006 at 11:04AM EST, Ludwig Max Brinckmann said:
> > >
> > > I noticed there is a resolution array in Google.js -- maybe this is out of
> > > date. If so, has someone new data for this and how was it calculated in the
> > > first place?
> >
> > It might well be out of date. I think GMaps goes up to zoom level 24
> > or so now in some places -- but only for aerial imagery? You might try
> > extending the Layer.Google resolution array locally and see what it
> > does. You might also need to change maxZoomLevel in your
> > OpenLayers.Map options.
> >
> > In any event, Google Maps resolutions are precisely a factor of two
> > apart. So if you want to extend the resolution array, halve each
> > resolution sucessively.
> >
> > SDE
> >
> >
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