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Line Density Tool output cell size not equal to specified parameter

LaurieKurilla1

I have created numerous line density maps of geologic faults with ArcGIS Pro Line Density tool. I specify a cell size and a search size. e.g. 5 and 25; 25 and 50 respectively and always specify output "area units" as 'square kilometers' . The resulting raster never has a unit cell size (5 or 25) that I specified. It is always considerably larger. The fault layer is WGS 1984 geographic coordinate.

Also, shouldn't the resulting unit output value (km/sq km) always be the same regardless of the cell size or search area size? I am getting different results for each run with different parameters.

Thank you
Laurie

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Accepted answers

danretired

Laurie .... consider km per sq km to be a convenience expression. If your x, y and z values are in meters, then you expect the numeric expression to be proportional to converting area from m^2 to km^2 etcetera.

When you start mixing geographic coordinates and/or imperial/US units, I prefer to do the proper prep step and convert everything myself rather than rely on assumptions of conversion (unless you test yourself.)

All comments

LaurieKurilla1

Dan,
Thank you for your prompt response. My question related to using different
cell and search sizes. For example, on one run I used 5 km output cell
size and 25 km search size. On another run I used 5 km cell size and 50 km
search size. Shouldn't both of these return the same unit density of x km
per sq km ?

Thanks
Laurie

danretired

LaurieKurilla1

Thank you Dan. I will review that documentation again and follow your
recommendations. Am I wrong in expecting the resulting unit density (km
per sq km) to be the same regardless of the cell and search size used?

Thank you
Laurie

danretired

A lot can go wrong if you don't use projected data in the first place or forget to specify the projected output coordinate system in lieu of that. I would also have a look at the cell size projection method mentioned in the help topic since it will have an impact on the resultant raster.

Line Density (Spatial Analyst)—ArcGIS Pro | Documentation

My suggestion... project the raster first ensuring that you get cell sizes in meters squared, then run the line density tool

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