[Gdal-dev] Newbie question

Frank Warmerdam warmerdam at pobox.com
Fri Mar 21 11:35:54 EST 2003

s duclos wrote:
> If the BSB chart is a mercator then the convention
> is north up.
> I'm not mutch into BSB so maybe when you say
> "don't desribe a perfect north up" 
> you mean that in a mathematical sens.
> But if you mean that the error is greater then
> what should be expected then a think there is
> problem.
> I think that CHS paper chart are printed from NTX
> data format. Don't know how this data is translated
> to BSB thought.


The BSB files contain a set of control points, normally referencing
locations on the chart to WGS84 lat/long locations as far as I can tell.
I am unable to derive an low error (less than one pixel) affine geotransform
from these control points.

Perhaps the problem is that I am ignoring the projection information.  Perhaps
if I can parse the projections properly, I could reproject the control points
into the projection in question and generate an affine transformation.

I don't know when I will get to this. Despite the considerable interest I
have received from people about BSB format, no paying customer of mine has
ever expressed any interest in the format!  Tha means work on it mostly
comes after paid work.

Best regards,

I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at 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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