[OpenLayers-Users] Formula for calculating resolution?

[Linda Rawson]

Thanks you guys.  You are the greatest.

Linda Rawson


On 9/26/07, Arnd Wippermann <arnd.wippermann at web.de> wrote:
>
> Hello Linda,
>
> to get myself some knowledge with scales and resolutions, i have build a
> little example. The resolution for your extent must be 0.00009633333333333
> (= dx/WIDTH), then you get - with the right centerpoint - your area.
> Change in your resolutions 0.0000858306884765625 with 0.00009633333333333.
> One hint: to set own resolutions for google layers is not possible.
>
> To calculate scales for various units you must keep in mind to take the
> right factor. Also must dx/WIDTH=dy/HEIGHT.
>
> Einheit Faktor
> inches        1
> ft           12
> mi        63360
> m            39,3701
> km        39370,1
> dd      4374754
> in            1
>
> dpi       72
> Einheit   dd
> Faktor    4374754
>
> Left         -122,1655000
> Right        -122,1077000
> Top            43,0083000
> Bottom         42,9505000
> WIDTH         600          pixel
> HEIGHT        600          pixel
> dx              0,0578     LE
> dy              0,0578     LE
> Scale       30343,29374
> Resolution      0,000096333333
>
> Scale = dx/WIDTH * dpi * Faktor
> Resolution = dx/WIDTH
>
> I hope that will help to solve your problem.
>
> Mit freundlichen Grüssen
>
> Arnd Wippermann
> http://gis.ibbeck.de/ginfo/
>
>
> ________________________________
>
> Von: users-bounces at openlayers.org [mailto:users-bounces at openlayers.org] Im
> Auftrag von Linda Rawson
> Gesendet: Mittwoch, 26. September 2007 06:05
> An: users at openlayers.org
> Betreff: [OpenLayers-Users] Formula for calculating resolution?
>
>
> I have a legacy mapping system that I am trying to convert to openlayers.
> MG.  It is bad.
>
> Anyway, I have the following dimensions of a 600 X 600 window.
> var bounds = new OpenLayers.Bounds(-122.1655, 42.9507, -122.1077, 43.008);
>
> I need the four lat/lon corners to be exactly these numbers at a certain
> zoom level.  What would I set as the resolution in the resolution array to
> get this?
>
> My resolution array is the following:
>
> var layerResolutions =
> [0.703125,0.17578125,0.0439453125,0.0054931640625,0.0006866455078125,
> 0.00017
> 1661376953125,0.0000858306884765625,0.00004291534423828125,
> 0.000021457672119
> 140625,0.000010728836059570312];
>
> Thanks in advance,
>
> Linda Rawson
>
>
>
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