[gdal-dev] Problem saving/reading inf GCPs values in VRT

[Even Rouault]

Le mardi 26 mai 2015 11:00:21, Calogero Mauceri a écrit :
> Hi all,
> 
> we are having problems saving/reading GCPs values in a VRT file when
> those values are inf or nan. This problem is happening on Window
> platform while it is working as expected in unix systems.
> 
> We are setting the GCP values in a VRT dataset using the library
> function GDALSetGCPs. The inf values get saved into the VRT XML as
> "*1.#INF00000000E+000*" string
> 
> <GCPList Projection="PROJCS["unnamed",
>      GEOGCS["WGS 84",
>          DATUM["WGS_1984",
>              SPHEROID["WGS 84",6378137,298.257223563],
>              TOWGS84[0,0,0,0,0,0,0]],
>          PRIMEM["Greenwich",0],
> UNIT["degree",0.0174532925199433]],
>      PROJECTION["Orthographic"],
> PARAMETER["latitude_of_origin",71.331088221],
> PARAMETER["central_meridian",-156.63420306],
>      PARAMETER["false_easting",0],
>      PARAMETER["false_northing",0]]">
>      <GCP Id="0" Pixel="0.0000" Line="0.0000" X="*1.#INF00000000E+000*"
> Y="*1.#INF00000000E+000*" />
>      <GCP Id="1" Pixel="363.0000" Line="0.0000" X="-3.463981152302E+004"
> Y="3.246591123662E+004" />
>      <GCP Id="2" Pixel="725.0000" Line="0.0000" X="-1.070555064325E+004"
> Y="1.097994383230E+004" />
>      <GCP Id="3" Pixel="1088.0000" Line="0.0000"
> X="-5.461709489401E+003" Y="6.277974169290E+003" />
>      <GCP Id="4" Pixel="1450.0000" Line="0.0000"
> X="-3.134437286904E+003" Y="4.191819043427E+003" />
>    </GCPList>
> 
> when those values are read through the GDALGetGCPs library function,
> then the inf values are set to 1.0.
> Is this a bug in GDAL or are we setting the inf GCP values in the wrong
> way?
> 
> Note that on unix everything works fine, the inf values are saved as
> "INF" strings in the VRT XML and they are properly converted when they
> are read back.

Calogero,

Dealing with Inf or NaN serialized number on Windows require special cases. 
But I fail to see why you need to set GCPs at infinity or nan, and I'd bet the 
behaviour of the TPS or polynomial transforms will be pretty much undefined 
with such as value.

Even

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