[gdal-dev] TOC sub-dataset retrieving when frame with same coverage share the same boundary rectangle.

[Andreas Oxenstierna]

Hi

A RPF structure (CADRG, CIB, ECRG etc) may include any combination of 
scalelevels and/or geographic zones as referenced in the A.TOC file. So 
there may be both scale-overlaps and zone-overlaps.
There is also a frame-based update concept but this is seldom used.
An example from a CADRG dataset containing 14 subdatasets:
SUBDATASET_6_NAME=NITF_TOC_ENTRY:CADRG_TFC_250K_6_5:A.TOC
SUBDATASET_6_DESC=CADRG:TFC:Transit Flying Chart (UK):250K:6:5
SUBDATASET_7_NAME=NITF_TOC_ENTRY:CADRG_LFC-FR_(Day)_500K_1_6:A.TOC
SUBDATASET_7_DESC=CADRG:LFC-FR (Day):Low Flying Chart (Day) - Host 
Nation:500K:1:6

This means that you must analyze the individual subdatasets to 
extract/combine info for each scalelevel individually. To my knowledge, 
there is no consistent naming principle in the standard - so the 
scalelevels are just logical names in the A.TOC file.
There should be overlaps between the zones but this data content "shall 
be identical".

Best Regards

Andreas Oxenstierna

> Selon Nicolas G <nicolas.g-dev at outlook.fr>:
>
> hi
>
> yes you have well described the behaviour of the driver. The
> subdatasets match the boundary rectangles
> And it is very odd to have two frames with same col row
> coordinates for the same boundary rectangle.
> in your case you have to directly open the nitf tile instead
> of the a.toc
>
>> Hi,
>>
>>
>>
>> I?m using GDAL to get the CADRG database sub-dataset list.
>>
>>
>> As an example (TOC file content):
>>
>> - Only one boundary rectangle defined in ?boundary rectangle section?,
>>
>> - In ?frame file index section?, I have two frames covering the same
>> area (same resolution, ?, but different functional content),
>>
>> - These two frames are stored in different path but all referring to the
>> same boundary rectangle.
>>
>>
>> Then in that case, the message "Frame entry(%d,%d) for frame file index
>> %d was already found." is raised by GDAL when loading the TOC file, and
>> finally
>> only one sub-dataset is given back to me(the first one of the TOC file) ->
>> method ?RPFTOCReadFromBuffer()? of Rpftocfile.cpp.
>>
>>
>> It seems that GDAL uses boundary rectangles and frame files to build the
>> sub-dataset list and if, for a same boundary rectangle, two or more frames
>> with
>> the same coverage belong to different path
>> then only one GDAL sub-dataset is created.
>>
>>
>> Does someone can help me and explain me how to access the data of these
>> two frames files (same coverage, same boundary rectangle but different path)
>> through GDAL API?
>>
>>
>> Or is there any development on this subject?
>>
>>
>>
>> Thanks,
>>
>>
>>
>> Nicolas
>>
>>
>>
>>
>>
>>
>
>
>
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