[gdal-dev] Problem with gdalsrsinfo on some NOAA bsb/kap files
Chris Barker
chris.barker at noaa.gov
Fri Nov 9 18:22:21 PST 2012
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
NOAA/NOS/OR&R (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception
Chris.Barker at noaa.gov
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