Raster Calculator Error between V23.1 and V26.0

burt46

Hi,

We have been trying to find why two different users were obtaining different outputs using the Raster Calculator even when using the input and output settings. The issue appears to be a variation in the version of the software which indicates a bug if the input conditions are the same. The multi-band image is generating the issue, even is 16 bit is selected for "Create Multi-Band Image with Vales of Bit Depth" and 16 bit is selected for "Bit Depth at Which to Sample Input Layers". As per the screenshots, the V26.0 has a slightly different menu where 32 bit is possible in the menu option, but even if 16 bit is selected it does not give the same output. V23.1 produces a very pixulated product and the V26.0 provides the as expected output for the band maths. This is a simple Band + Band equation, so nothing complicated.

Is there a workaround for this with V23?

V23.1.png

V26.0.png

burt46

Hi, any feedback on this one please? Is there a workaround with using the scripting function?

bmg_mike

Is it possible for you to provide the input data that is resulting in this issue, either here or to geohelp@bluemarblegeo.com ?

There must be some change between v23.1 and v26.0 that is resulting in the difference. It looks like most of the significant changes to the Raster Calculator between those versions were made in the v24.0 release back in Sept 2022.

Of course, the simplest solution if possible is to upgrade the v23.1 installation to the latest (26.1) version.

Thanks,

Mike

Global Mapper Guru

burt46

Hi Mike, i cant share the data as i signed a NDA. I am quite confident that if you used any B3 and B4 data set and processed the data as a simple B3 + B4 calculation you would get a similar error. Attached is an area to show the visual variations. The pixel values are completely different. V23.1 does not appear to generate the multiband, even when selected.

Paying to upgrade to solve a bug is not really ideal.

V23.1 Output - Copy.png

V26.0 Output - Copy.png

bmg_mike

Hi Burt,

I was able to reproduce the issue in v23.1, and found that it was fixed in v24.0 and later.

As a workaround in v23.1, I used the settings below to create a 16-bit integer shaded layer and that had the correct values. You could then export that 'elevation grid' to something like a GeoTIFF with 16-bit samples or maybe a BIL, then load that back in. Or you could set the shader to a Gradient Shader to get a grayscale display of the values.

Thanks,

Mike

Global Mapper Guru