Global Mapper Grid Elevation Reclassification

AxelG

Hi,

Does anyone know the correct procedure for reclassifying values for a GMG?

I’m working with a change-detection raster created by subtracting two DEMs. My goal is to calculate cut-and-fill volumes along line segments to analyze erosion and deposition. I’m using the volume calculation tool with a 10 m corridor around the line and a sample spacing of 0.30 m × 0.30 m in the X and Y directions. All vertices have a base height of 0 m.

The issue is that the raster has a lot of noise within the –0.30 m to +0.30 m range. I assumed these values would be excluded because I applied a custom shader that hides values within that range, but the shader settings don’t seem to affect the volume calculation—the tool still uses the full range of values. The volume tool allows setting X and Y sample spacing, but not Z.

What is the proper way to reclassify or filter out small elevation changes before running the volume calculation? Raster reclassification?

My goal is to calculate volumes at a sample spacing of 0.30m in the x, y, and z axis .

Thanks GM forum.