[Gdal-dev] need tools for TIF image reprojection

[Zhonghai Wang]

Hi Andrew,

you are right, in the most cases the GDAL utilities work well, and I've also
use the GDAL utilities for a long time, especially the FWTools made by
Frank, we should all thank Frank for such a wonderful GIS toolkit.

I've check again and again with the GDALWARP, but things are not going in
the right way. I am trying to translate the TIF images from the coordinate
system CH1903 (Swiss National System) to ETRS89 / UTM ZONE 32N, and there
are always  some displacement with the base maps, I am sure that the base
map and the original coordinate info for the TIF is correct. and here is an
example:

(the transforming process is : CH1903 -> WGS84 -> ETRS89 / UTM ZONE 32N)

the TIF image coordinate Info (*.tif): (Swiss National System)
 0.500000
 0.000000
 0.000000
 -0.500000
 598125.250000
199999.750000

If I transform the coordinate to WGS84 with GDAL, the value is:

0.0000059839
0.0000000000
0.0000000000
-0.0000059839
7.4149523128
46.9529994915

but the lon/lat of the upper left corner should be:

7.41401039348263
46.9510762167473

I would say that this is already big difference, because If I use this
lon/lat to get the UTM coordinate, this small difference will be propagated,
and will cause a displacement about hundreds meters.

I am trying to find the source code, which does this coordinate
transformation, so that I can check if the transformation parameters are
correct, but unfortunately I can not find the source for this.


If someone has done something similar, please point me out how to fix this
problem, especially the GIS people in Switzerland. I would really appreciate
it.

zhonghai

On 7/14/06, Andrew Williams <awilliams at rapidmap.com.au> wrote:
>
> zhonghai,
> I've litterally translated hundereds of TIF's from all over the world from
> multiple projections to multiple projections. I have also had "failures".
> However, in every case, it was either my fault in specifying the -s_srs or
> -t_srs. In some cases the fault lay in the original image. The TIFF itself
> was supplied with incorrect georefernceing information and so it was never
> going to work.
>
> Have you got a dump from GDALINFO that we can see and the GDALwarp command
> line you've used?
>
> regards
> Andrew
>
>        -----Original Message-----
>        From: Zhonghai Wang [mailto:zhonghaiw at gmail.com]
>        Sent: Fri 7/14/2006 12:14 AM
>        To: gdal-dev at lists.maptools.org
>        Cc:
>        Subject: [Gdal-dev] need tools for TIF image reprojection
>
>
>        Hi guys,
>
>        I need a tool to reproject my TIF images, either free or non-free
> software.
>        I've tried with the GDAL utilities, sure I can do the reprojection,
> but the coordinates seems not correct, there are serveral hundert meters
> displacement according to the my base maps.
>
>        thanks for your info.
>
>        zhonghai
>
>
>
>
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