CALC_VOLUME_BETWEEN_SURFACES producing different results than CALC_VOLUMES of subtracted elevations

luiender

I wish to measure the volume difference between two elevation models of the same area. I can either a) measure the volume between the two surfaces or b) subtract the surfaces from each other to create an elevation model of the differences, and then measure the volume change from z=0 plane.

Unfortunately when using Global Mapper scripting the results are wildly different. The two scripting files for each method are:

a)
```

GLOBAL_MAPPER_SCRIPT VERSION=1.00 SHOW_WARNINGS=YES LOG_TO_COMMAND_PROMPT=YES

LOG_MESSAGE Starting...

IMPORT FILENAME=%DEM% TYPE="GEOTIFF"

DEFINE_VAR NAME="MINE_SHAPE" VALUE=%SHAPEFILE%

IMPORT FILENAME="%MINE_SHAPE%"

CALC_VOLUMES FILENAME=%MINE_SHAPE% OUTPUT_FILENAME="%CSV%"
```

```

GLOBAL_MAPPER_SCRIPT VERSION=1.00 SHOW_WARNINGS=YES LOG_TO_COMMAND_PROMPT=YES

LOG_MESSAGE Starting...

IMPORT FILENAME=%DEM1% TYPE="GEOTIFF"

IMPORT FILENAME=%DEM2% TYPE="GEOTIFF"

IMPORT FILENAME=%SHAPEFILE% "

CALC_VOLUME_BETWEEN_SURFACES LAYER1_FILENAME=%DEM1% \

LAYER2_FILENAME=%DEM2% \

AREA_FILENAME=%SHAPEFILE% \

OUTPUT_FILENAME="%CSV%" \
```

luiender

Method A results: https://pastebin.com/raw/5wwS4y9p

Method B results: https://pastebin.com/raw/0G4Pc4wY

Method B produces the results I am looking for. However Method A is the better process. Can someone please let me now what I'm missing for the data to be so different?

Cheers

Mark Gale

Hi luiender, I believe your question is similar to one I posed on here a few years ago. This thread may help: https://www.globalmapperforum.com/discussion/11974/cut-and-fill-volumes#latest Cheers