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lutraconsulting / serval

QGIS plugin for setting raster pixel values
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Unable to change values #28

Closed tedrigby closed 3 years ago

tedrigby commented 3 years ago

Hi

I am running W10 and QGIS 3.16.4 and recently installed serval to modify some cells in my ascii grid topography file. I have tried all of the recommended selection and reset approaches mentioned in the manual but although the blue circle appears as if it is changing the elevation value - applying the probe to check afterward shows no change. Is there a problem or have I just not approached selection/adjustment in the right order? It is as if the ascii grid file is not available for writing.

Many thanks

Ted Rigby

erpas commented 3 years ago

Hi Tom,

yep, the ASCII grid is a read-only format: https://gdal.org/drivers/raster/aaigrid.html#raster-aaigrid Try to convert it to another format, for example TIF, and you should be able to modify it.

Kind Regards,

Radek Pasiok

tedrigby commented 3 years ago

Thanks Radek

I tried converting to geotiff and yes serval then worked fine. Thanks for your speedy response.

Is there some reason why QGIS/Serval does not support writing to an ascii grid – seems odd given the wide use of ascii grid formats in civil engineering as an elevation layer. I am a split Global Mapper – QGIS user and can easily export a non ascii raster to ascii grid format in Global Mapper so was not expecting problems writing to a grid in QGIS/Serval?

Ted

From: Radek Pasiok @.> Sent: 16 March, 2021 7:40 PM To: lutraconsulting/serval @.> Cc: Ted @.>; Author @.> Subject: Re: [lutraconsulting/serval] Unable to change values (#28)

Hi Tom,

yep, the ASCII grid is a read-only format: https://gdal.org/drivers/raster/aaigrid.html#raster-aaigrid Try to convert it to another format, for example TIF, and you should be able to modify it.

Kind Regards,

Radek Pasiok

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erpas commented 3 years ago

QGIS depends on GDAL in it, so it would be question for its developers.