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Hello All,

I have a group of many TIF tiles with associated TABs which I open via a seamless table in MapInfo. I can open the TIFs directly in QGIS and they are correctly registered. However, I want to be able to create the equivalent of a MapInfo seamless table that can be used in QGIS. Would this be a Virtual Raster Catalog? And do you know how to create this in FME? I've tried the RasterMosaicker to produce an ECW but I get a warning (and this just creates a whole new (big) file anyway so not ideal):

TIFF reader: TIFFFetchNormalTag:ASCII value for tag "ImageDescription" contains null byte in value; value incorrectly truncated during reading due to implementation limitations

And error:

ECW writer: This format cannot support palettes. Consider removing or resolving palettes that are attached to the raster

When I try to build a Virtual Raster Catalog in QGIS I get the following error for each tile:

Warning 1: TIFFFetchNormalTag:ASCII value for tag "ImageDescription" contains null byte in value; value incorrectly truncated during reading due to implementation limitations

 

Warning 6: gdalbuildvrt does not support rotated geo transforms. Skipping C:\\Users\\Temp\\04027131.TIF

Sorry, but I'm not that knowledgeable about rasters - does this mean there's no geographical information attached to the tile ie they are not geotiffs? How does QGIS register them if this is the case? And how can I use FME to get around this?

Many thanks,

Jane

Hi @janem thanks for your question!

 

I think you're right that TIFF > RasterMosaicker > ECW is not the way to go if you're looking for a virtual raster. I can't speak too much to the QGIS errors, but take a look at the GDAL Documentation (QGIS docs are pretty lacking, but I think the Virtual Raster Catalog tool just uses the GDAL tool) and this very old question for some insights. Maybe posting a new question to the GIS Stack Exchange might would get some more current answers.

 

 

One thing that might be worth a try is testing a few of your TIFFs in a TIFF > geoTIFF conversion in FME, then trying those geoTIFFS with the Virtual Raster Catalog tool. If you run into palette or rotation/transformation errors when converting to geoTIFF we can help with those - we have dedicated raster transformers for working with palettes and transformations.

 

 

While we do read GDAL VRT files (likely the same or similar to what the QGIS tool makes), we don't write them. I'd suggest contributing to this idea or creating a new one if you think it's a feature we should add.

 

 

Hope this helps!

 

Nathan

Many thanks for your reply Nathan. There's a lot to think about here - the link to the old question was interesting as the problem is very similar to my own. When I next find time I will try a

TIFF > geoTIFF conversion in FME followed by the Virtual Raster Catalog tool in QGIS. I'll try GIS Stack Exchange too.

Thanks again! Jane

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