Brenna

Question

Before analyzing a DEM with statistical tools like zonal statistics, I want to make sure the DEM is as accurate as possible. I was told that filling sinks before analysis is just good practice and I want opinions on this with literature attached if possible. I will also be trying to calculate the RMSE of the filled DEM and correct for error if possible. I have never done this before so any help is welcome.

BrennaOlson · Answer

To clarify, I'm working to better delineate the elevation ranges of 12 snakes. I'm not doing any hydrological analysis, I just want to look at how toppgraphy and horizontal point accuracy impact extracted elevation values. I'm using zonal statistics to look at the ranges of elevation values within a variety of buffers around points. For this purpose, is filling depressions good practice? My feeling is that it is but I want to confirm with other profesionals.

JayantaPoddar · Answer

Sinks (and peaks) are often errors due to the resolution of the data or rounding of elevations to the nearest integer value.

Sinks should be filled to ensure proper delineation of basins and streams. If the sinks are not filled, a derived drainage network may be discontinuous.

How Fill works

Planchon, O., and Darboux, F. 2002. "A fast, simple and versatile algorithm to fill the depressions of digital elevation models." Catena 46(2): 159–176.

Tarboton, D. G., R. L. Bras, and I. Rodriguez–Iturbe. 1991. "On the Extraction of Channel Networks from Digital Elevation Data." Hydrological Processes 5: 81–100