[OpenLayers-Users] combine 2 different projections map data

[Marc Jansen]

Hi Aypes2,

why don't you reproject your cad files to //EPSG:3785 (EPSG:900913, that 
is) when you already serve them from a mapserver?

If you experience problems doing that, the Mapserver mailinglist may help.

Regards,
Marc



Aypes2 wrote:
> Dear all,
>
> I recently encountered a problem of putting different projections maps in
> openlayers. I use my own CAD files (DGN) with HK 1980 Grid system
> (EPSG:2326) and google satellite map. I want to compose them as base layers.
> However, their coordinates system are largely different.
>
> For my Cad files, the projected bound coordinates is around (806677.9759,
> 802420.9858, 876817.5647, 853384.7903). In my map file (I use MapServer), I
> set the projection "init="epsg:4326" to project the map. It renders well.
> But I do not know why it works, as 4326 should use longitude and latitude
> for the display.
>
> But for google map, it uses epsg:900913. I tried to put
> sphericalMercator':true statement in Google map layer and the coordinates of
> my target place is around 
> (12657054, 2518447, 12765595, 2586476).
>
> So two maps do not match.
> I know transformation of projection is needed. Is it possible to reproject
> the google map into my coordinate system? Or how can I transform my CAD
> system projection into longitude & latitude or epsg:900913? I tried to put 
> "Projection: new OpenLayers.Projection("EPSG:900913"),"   in map option of
> Openlayers and (init="epsg:900913") in mapfile (extent also changed), but
> they don't work.
>
> Thanks,
> Aypes2
>   


-- 


  Dipl.-Geogr. Marc Jansen
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