[Gdal-dev] Dealing with RPC offsets and parameters in GDAL

[Ozy Sjahputera]

Frank,

my colleagues and I were given a set of NITF images.  We found that the
pan and multispectral image of the same scene do not always
co-registered correctly.  When this happens, we found that some of the
RPC parameters in the two images, such as RPC_LONG_OFF, RPC_LONG_SCALE,
RPC_LAT_OFF, RPC_LAT_SCALE, RPC_HEIGHT_OFF, and RPC_HEIGHT_SCALE, hold
different values. 

We thought that we can correct the co-registration problem by *somehow*
matching the values of these RPC parameters in both pan and MS. 
Changing these parameters would be done by applying some RPC-based
transformation, correct?

Do you have any information or examples on how to deal with RPC-based
transformation in GDAL?

I have found some RPC related functions in GDAL, such as
GDALCreateRPCTransformer().  I am still tracing how to get the
GDALRPCInfo object needed by GDALCreateRPCTransformer().  I have found a
function called GDALExtractRPCInfo() in gdal_misc.cpp that takes a char
** , extracts the RPC parameters from the string array, and saves them
in a GDALRPCInfo object.  But I am still unclear how to obtain the
string array containing the RPC parameters from the image metadata of an
NITF image.

Any info on RPC related functions in GDAL you can share with me will be
very helpful.

Thank you.

Ozy