Re: [gdal-dev] Re: GCP list projection

2011-02-18 Thread Chaitanya kumar CH 
Vadim,

(0,1,0,0,0,1) is the default transform and will be returned even in case of
an error.

On Fri, Feb 18, 2011 at 2:09 PM, Vadim Shlyakhov vadp.d...@gmail.comwrote:

 Frank Warmerdam warmerdam at pobox.com writes:


  In theory it could make sense to have a dataset with a dataset level SRS
  and geotransform, and also GCPs with a different SRS.  In some cases the
 GCPs
  are in a particular SRS (say lat/long) just because it is a convenient
  coordinate system to collect the GCPs, not because it is representative
 of
  the geometry of the image.

 Thanks Frank, That was actually my understanding. BSB and Ozi have their
 GCPs in
 long/lat, so I thought that a feature for such a case.

 So, if you have GCP SRS, you don't need SRS set at the dataset level, do
 you?

 BTW I've noticed if a dataset doesn't have a geotransform, then
 ds.GetGeoTransform() returns (0.0, 1.0, 0.0, 0.0, 0.0, 1.0). Is that a
 feature
 or a bug?



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Re: [gdal-dev] Re: GCP list projection

2011-02-18 Thread Frank Warmerdam 

On 11-02-18 03:39 AM, Vadim Shlyakhov wrote:

So, if you have GCP SRS, you don't need SRS set at the dataset level, do you?


Vadim,

Correct.


BTW I've noticed if a dataset doesn't have a geotransform, then
ds.GetGeoTransform() returns (0.0, 1.0, 0.0, 0.0, 0.0, 1.0). Is that a feature
or a bug?


As mentioned, this the fallback value when there isn't one.  But the method
should return CE_Failure on failure so you can distinguish whether the
unity transform is real or just a filler value.

So I consider it a feature.

Best regards,
--
---+--
I set the clouds in motion - turn up   | Frank Warmerdam, warmer...@pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush| Geospatial Programmer for Rent

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