topic Re: Cut Fill Error Margin in ArcGIS Spatial Analyst Questions

Cut Fill Error Margin

KaraLamantia — Thu, 15 Feb 2018 21:59:40 GMT

I'm using the Cut and Fill tool in the 3D analyst toolbox to find the difference in volume between two sets of raster files.

I'm wondering if there is some sort of error margin that is possible each time I run the tool? For instance, does it round values so there might be an error of 0.5 meters in each pixel?

Very familiar with the tool and the 3D toolbox, but I have yet to find anything beyond the basic description of how the tool works

Re: Cut Fill Error Margin

DanPatterson_Retired — Thu, 15 Feb 2018 22:53:59 GMT

Not sure I follow, but since you are working with rasters and raster representation of geometry, then there is an inherent approximation. What sort of cell size are you working with?

Re: Cut Fill Error Margin

KaraLamantia — Thu, 15 Feb 2018 23:13:54 GMT

The entire area is a few square kilometers. I was assuming there is some sort of approximation, but I was hoping to quantify that for research publishing purposes

Re: Cut Fill Error Margin

DanPatterson_Retired — Fri, 16 Feb 2018 00:03:44 GMT

Kara... I meant the size of each raster cell. If the cell size is 1 meter (aka cell width), then area is 1m^2 and volume 1m^3. If you are delineating an area, then the boundary 'replication' is going to better the smaller the cell size, hence area and volume would be better 'estimates'. If people don't specify the cell size when using any tool in ArcToolbox's Spatial Analyst extension, then the cell size is determined as 1/250th the width/height. So for a 1 km boundary edge, that would be 4 metres in length, 16m^2 in area etc. Is that good enough? If not, you use a finer cell size and weigh the benefits of that versus data processing issues. Of course, the totally leaves out how well any process is an actual representation of what it is purporting to measure.

Re: Cut Fill Error Margin

KaraLamantia — Fri, 16 Feb 2018 14:36:50 GMT

Dan,

My cell size is about 5m, the raster themselves are derived from a series of mass point measurements across the surface of a glacier. We're looking at volume loss over time.

Re: Cut Fill Error Margin

DanPatterson_Retired — Fri, 16 Feb 2018 14:51:30 GMT

Kara, if you are looking for some volume change +/- some margin of error, then the error would lie in the accuracy of those measures from the mass points. The precision (fineness) of the raster is simply how it represents those measures.

Re: Cut Fill Error Margin

KaraLamantia — Fri, 16 Feb 2018 14:53:31 GMT

Okay, that is what I originally thought, but I just wanted to make sure I wasn't missing something. Thank you for your help!

Re: Cut Fill Error Margin

DanPatterson_Retired — Fri, 16 Feb 2018 15:29:49 GMT

No problem Kara