What is TileHintX or TileHintY metadata provided by OTB

OTB Usage
1

Hello,

Geotiff written by OTB included a metadata info which is TileHintX and TileHintY: I did not find anything explaining what are these metadata (also search on gdal).

Metadata:
  AREA_OR_POINT=Area
  DataType=4
  METADATATYPE=OTB
  OTB_VERSION=8.0.1
  TileHintX=*
  TileHintY=1

The main problerm is that when using gdalwarp on two chuncks written by OTB, it leads to strange value (e.g. TileHintX=*) and then it is not possible anymore to process the geotiff using BandMath for instance. We need to rewritte the metadata using gdal_edit.py to continue the processing.

Also, when using gdal_merge, these metadata (TileHintX) is not propagated. I am wondering to what kind of information these values are related, and if it is possible to tell otb to not write these.

2

I found in the OTB source code (otb/Modules/Core/Common/include/otbImageRegionAdaptativeSplitter.h) that TileHintX is related to some data compression (jpg2000).

For my situation, the problem can be solved by using -cvmd option in gdalwarp to manage metadata conflict between merged data set and prevent having * as metadata.

However, OTB does not seem to be able to open geotiff with metadata TileHintX=*, while gdal is.

3

Hello @MathieuF ,

Do you know which OTB application has written this metadata? it really doesn’t look regular.
AFAIK tile hints are just convenience processing metadata (e.g. hinting that JP2000 tile is NxN).

4

Hi @remi.cresson

Sorry if I was not clear: the* in ThileHintX=* was written by gdalwarp. It is the default behavior when conflictig metadata.

The ThileHintX metadata is written by several otb app (ImageClassifier and BandMath) with python wrapper.

With iota2 (iota2-project / iota2 · GitLab) tile chuncks are processed in parallel: for some processing, we use otb app as final task, and use internal otb writter to save the chuncks : in that case we have the TileHintX metadata, and then when merging gdalwarp leads to * issue. In other case, rasterio is used, and we don’t have TileHintX metadata, and thus no problem with gdalwarp.

For now, the problem is solved by specifiying option in gdalwarp.

But more generally, OTB does not seem to be able to open geotiff with metadata TileHintX=*. (for OTB version 8.0.1).

I hope it is more clear now.

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