[OpenLayers-Users] combine 2 different projections map data

[Aypes2]

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
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