[gdal-dev] Fwd: Bounding box change in recent versions of gdal?

[Even Rouault]

Le samedi 03 septembre 2011 12:23:55, Ole Nielsen a écrit :
> Dear all!
> 
> This may be related to my recent posting about SetField behaving
> differently in different gdal versions.
> In any case I find that the bounding box of this test geotif
> file<http://www.keepandshare.com/doc/3116689/population-2010-clip-tif-septe
> mber-3-2011-5-20-pm-162k?da=y> is
> different on the two installations (details below).
> 
> In brief, the bounding box using gdal 1.6 is
> 
> Upper Left  (  99.3641696,  -0.0041806) ( 99d21'51.01"E,  0d 0'15.05"S)
> Lower Left  (  99.3641696,  -2.2031806) ( 99d21'51.01"E,  2d12'11.45"S)
> Upper Right ( 102.2411696,  -0.0041806) (102d14'28.21"E,  0d 0'15.05"S)
> Lower Right ( 102.2411696,  -2.2031806) (102d14'28.21"E,  2d12'11.45"S)
> Center      ( 100.8026696,  -1.1036806) (100d48'9.61"E,  1d 6'13.25"S)
> 
> 
> whereas using gdal 1.8 it is
> 
> Upper Left  (  99.3600000,   0.0000000) ( 99d21'36.00"E,  0d 0' 0.01"N)
> Lower Left  (  99.3600000,  -2.1990000) ( 99d21'36.00"E,  2d11'56.40"S)
> Upper Right ( 102.2370000,   0.0000000) (102d14'13.20"E,  0d 0' 0.01"N)
> Lower Right ( 102.2370000,  -2.1990000) (102d14'13.20"E,  2d11'56.40"S)
> Center      ( 100.7985000,  -1.0995000) (100d47'54.60"E,  1d 5'58.20"S)
> 
> It'd be great if someone can
> 
>    1. Reproduce this using the test file (download using link above)
>    2. Let us know which bounding box is correct
>    3. Raise this as a ticket if it is a genuine bug

Ole,

I've not tried with your file but the output of gdalinfo is sufficient to explain 
the difference you see.

It is due to a fix done in GDAL 1.8.0 that changes the way the 
AREA_OR_POINT=Point metadata is interpreted w.r.t geotransform.

It is mentionned in the GDAL 1.8.0 NEWS :

== Backward compatibility issues ==
[...]
* RFC 33 changes the way PixelIsPoint is handled for GeoTIFF (#3838,#3837)

You will find more information here : 

http://trac.osgeo.org/gdal/wiki/rfc33_gtiff_pixelispoint

Best regards,

Even