[gdal-dev] different results for vector and raster data reprojections

[Markus Neteler]

Nimalika,

On Fri, Feb 27, 2009 at 8:42 PM, nimalika fernando <nimalikaf at gmail.com> wrote:
> Hi,
>
> I have used ogr2ogr to assign projection information(SL99) to some vector
> data which does not contain any projection information.

How did you do that? Please post the details.

> I used the same projection information to reproject a raster in UTM 44N to
> SL99.Both data sets contain data of same location.
>
> When I try to overlay the projected data  ( using QGIS where the SL99 is
> defined using the same projection information) there is a small shift in two
> layers.

This may be an indicator for the datum not being recognized properly.

> When check the projection information using ogrinfo/gdalinfo I found that
> even though the same parameters are used for projection of vector and raster
> data , some parts of the WKT is different. I am not sure whether this is the
> reason for the problem in overlapping.

It might be - the "morphing" of similar names might fail.

> The resulting WKT are as follows
>
> Raster
>
> PROJCS["Transverse_Mercator",
>     GEOGCS["Everest 1830",
>         DATUM["unknown",
>             SPHEROID["unnamed",6377276.345,300.8017000000115]],
>         PRIMEM["Greenwich",0],
>         UNIT["degree",0.0174532925199433]],
>     PROJECTION["Transverse_Mercator"],
>     PARAMETER["latitude_of_origin",7.00047],
>     PARAMETER["central_meridian",80.77171],
>     PARAMETER["scale_factor",1],
>     PARAMETER["false_easting",200000],
>     PARAMETER["false_northing",200000],
>     UNIT["metre",1,
>         AUTHORITY["EPSG","9001"]]]
>
> Vector
>
> PROJCS["Transverse_Mercator",
>     GEOGCS["Everest 1830",
>         DATUM["unknown",
>             SPHEROID["evrst30",6377276.345,300.8017]],
>         PRIMEM["Greenwich",0],
>         UNIT["Degree",0.017453292519943295]],
>     PROJECTION["Transverse_Mercator"],
>     PARAMETER["latitude_of_origin",7.00047],
>     PARAMETER["central_meridian",80.77171],
>     PARAMETER["scale_factor",1],
>     PARAMETER["false_easting",200000],
>     PARAMETER["false_northing",200000],
>     UNIT["Meter",1]]
>
> Can anybody help me to identify what went wrong  ?

please post more details (see above).

Markus