[gdal-dev] RPC transform

[Dmitry Baryshnikov]

Hi Ivan,
Look here: 
http://www.gdal.org/gdal__alg_8h.html#af4c3c0d4c79218995b3a1f0bac3700a0

You can find such options:

  *

    RPC_HEIGHT: a fixed height offset to be applied to all points passed
    in. In this situation the Z passed into the transformation function
    is assumed to be height above ground, and the RPC_HEIGHT is assumed
    to be an average height above sea level for ground in the target scene.

  *

    RPC_HEIGHT_SCALE: a factor used to multiply heights above ground.
    Usefull when elevation offsets of the DEM are not expressed in
    meters. (GDAL >= 1.8.0)

  *

    RPC_DEM: the name of a GDAL dataset (a DEM file typically) used to
    extract elevation offsets from. In this situation the Z passed into
    the transformation function is assumed to be height above ground.
    This option should be used in replacement of RPC_HEIGHT to provide a
    way of defining a non uniform ground for the target scene (GDAL >=
    1.8.0)

  * RPC_DEMINTERPOLATION: the DEM interpolation (near, bilinear or cubic)


Best regards,
     Dmitry

16.01.2013 19:54, Ivan Lucena ?????:
> Yehiyam,
>
> For that kind of issue my advise is to run in debugging mode. The GDAL 
> transformation engine must have an internal pixel geolocation defined. 
> It is probably CENTER of the pixel, as in AREA. I am not sure. In that 
> case the returning pixel/line refers to AREA and you might need to do 
> the adjustment. But again, I would debug it to make sure. We have 
> instructions on how to debug GDAL using VS and NetBeans on wiki. I 
> just can't find it. I can't find anything about the RPC_DEM either. 
> Where did you get it?
>
> Regards,
>
> Ivan
>
> On 1/16/13 7:40 AM, Livneh Yehiyam wrote:
>>
>> Hi
>>
>> I have a question about the RPC transform implemented in gdal_rpc.cpp.
>>
>> If a dem file is specified in the transform options (RPC_DEM) the 
>> file is sampled to retrieve the elevation of the transformed point.
>>
>> In the case where the dem file is a DTED file (which defines 
>> AREA_OR_POINT to POINT), shouldn't the pixel/line values in the dem 
>> file be offset by half a pixel to get the correct height?
>>
>> Thanks
>>
>> Yehiyam
>>
>>
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