Hello. Let me start by saying I'm not in the geo / topo / map etc field so I've been flying by the seat of my pants learning as I go to get what I need for the project I'm working on.
That said, I've obtained what I'm told are some 10 meter DEM (.ddf) files from which I've been outputting rasterized images. Problem is every format - JPG, PNG, TIF etc.. - are 8 bit in resolution, so even if I crank up the number of greyscale 'steps' (graduated color) in SAGA GIS those steps aren't rendered out. I've even been trying "Shade / Dark-Bright" for output and get the same results.
My ultimate goal is bringing the heightmap data into a 3D application to generate terrain geometry - the only problem is that once my geometry grid resolution matches the X,Y resolution of the raster image from SAGA GIS the "terracing" steppyness of the 8 bit export file format is revealed.
Any way I can tell SAGA GIS to spit out say, a TIFF in 16 bit? I know TIFFs are capable of handling up to floating bit values - I just can't wrap my head around this one.
Thank you,
Marc
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you can use the Import/Export - GDAL/OGR / "GDAL: Export Raster" module for this task. In order to export 16bit, you must first convert the SAGA grid to the appropriate data storage format. Use the Grid - Tools / "Convert Data Storage Type" module and convert your grid to "unsigned 2 byte integer". Then switch to the "GDAL: Export Raster" module and select "GeoTIFF" with the Format parameter and provide the following option with the Creation Options parameter:
NBITS=16
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Thank you so much for taking the time to walk me through that step by step. I had a brief moment to follow along and it looks like it's working. I do get a 16 bit image that is noticeably better in value grading. Excellent.
One thing I was doing when I was exporting 8bit images was setting something called "Classification" to "Set Range to Minimum / Maximum" to normalize the greyscale ramp - if I didn't, many of the quads had their maximum values / whites clipped. Setting Min Max restored the clipped areas. Min Max doesn't seem to want to behave the same way with the converted Grid now though - I can't take the dark 16 bit image and normalize it 'up' to white with this technique. I'm sure I can use Levels in Photoshop to do something similar (even 'crushed' the values exceed the old 8bit files) but I feel having it done in SAGA GIS would be the optimal thing to do.
What would you suggest?
Thank you again,
Marc
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The "Classification" settings are only altering the color palette, i.e. how the grid is displayed in saga_gui, not the values of your grid. I.e., these settings are not respected once you export your grid. Have a look at the Grid Calculus / "Grid Normalisation" and "Grid Standardisation" modules - these allow you to actually stretch the grid values.
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I just wanted to write and say thank you. This worked out great - your instructions / directions were really helpful for a noob like myself. I was super successful in the end.
Marc
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hello. Let me start by saying I'm not in the geo / topo / map etc field so I've been flying by the seat of my pants learning as I go to get what I need for the project I'm working on.
That said, I've obtained what I'm told are some 10 meter DEM (.ddf) files from which I've been outputting rasterized images. Problem is every format - JPG, PNG, TIF etc.. - are 8 bit in resolution, so even if I crank up the number of greyscale 'steps' (graduated color) in SAGA GIS those steps aren't rendered out. I've even been trying "Shade / Dark-Bright" for output and get the same results.
My ultimate goal is bringing the heightmap data into a 3D application to generate terrain geometry - the only problem is that once my geometry grid resolution matches the X,Y resolution of the raster image from SAGA GIS the "terracing" steppyness of the 8 bit export file format is revealed.
Any way I can tell SAGA GIS to spit out say, a TIFF in 16 bit? I know TIFFs are capable of handling up to floating bit values - I just can't wrap my head around this one.
Thank you,
Marc
Hi,
you can use the Import/Export - GDAL/OGR / "GDAL: Export Raster" module for this task. In order to export 16bit, you must first convert the SAGA grid to the appropriate data storage format. Use the Grid - Tools / "Convert Data Storage Type" module and convert your grid to "unsigned 2 byte integer". Then switch to the "GDAL: Export Raster" module and select "GeoTIFF" with the Format parameter and provide the following option with the Creation Options parameter:
Volker,
Thank you so much for taking the time to walk me through that step by step. I had a brief moment to follow along and it looks like it's working. I do get a 16 bit image that is noticeably better in value grading. Excellent.
One thing I was doing when I was exporting 8bit images was setting something called "Classification" to "Set Range to Minimum / Maximum" to normalize the greyscale ramp - if I didn't, many of the quads had their maximum values / whites clipped. Setting Min Max restored the clipped areas. Min Max doesn't seem to want to behave the same way with the converted Grid now though - I can't take the dark 16 bit image and normalize it 'up' to white with this technique. I'm sure I can use Levels in Photoshop to do something similar (even 'crushed' the values exceed the old 8bit files) but I feel having it done in SAGA GIS would be the optimal thing to do.
What would you suggest?
Thank you again,
Marc
The "Classification" settings are only altering the color palette, i.e. how the grid is displayed in saga_gui, not the values of your grid. I.e., these settings are not respected once you export your grid. Have a look at the Grid Calculus / "Grid Normalisation" and "Grid Standardisation" modules - these allow you to actually stretch the grid values.
Volker,
I just wanted to write and say thank you. This worked out great - your instructions / directions were really helpful for a noob like myself. I was super successful in the end.
Marc