[gdal-dev] Problem with gdalsrsinfo on some NOAA bsb/kap files

[Chris Barker]

On Fri, Nov 9, 2012 at 2:48 PM, Even Rouault
<even.rouault at mines-paris.org> wrote:

> ok, I see what happens. In _3 and _4 cases, the BSB driver manages to compute
> a geotransform from the GCPs and then assigns a projection, in addition to the
> GCP projection.
> In the _1 and _2 cases, the BSB driver doesn't manage to compute the
> geotranform from the GCPs (which is a known issue sometimes with this driver,
> presumably because it has a too strict tolerance in the computation of the
> geotransform from the GCPs), so the projection is only reported by the
> GetGCPProjection() method, which the gdalsrsinfo never queries.
>
> In all cases, gdalinfo does show the projection and/or GCP projection.
>
> Perhaps gdalsrsinfo should also query the GCP projection if no regular
> projection is reported.

I've wondered for ages about this driver -- the *.kap files have
redundant info -- the projection definition and related info is enough
(always? or only north-up?) to provide a complete projection and
geotransform, but there are also the set of GCPs.

I've never checked to see if they always match to a good tolerance,
and I don't know what  GDAL does with the redundant info.

>From your note, it sounds like GDAL prefers the GCP transform -- is
that so? and I'm not sure that's the best option -- presumably the
info in the header is exact? Why not prefer that?

-Chris




-- 

Christopher Barker, Ph.D.
Oceanographer

Emergency Response Division
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Chris.Barker at noaa.gov