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Upslope area functions

03 Aug 2007 (Updated 17 Sep 2009)

Code covered by the BSD License

Functions for computing and visualizing upslope area, influence map, dependence map

File Information
Description	A collection of functions for calculating the upslope area and related measurements for a digital elevation model (DEM). Based on the method of Tarboton. See also the upslope area postings on my image processing blog, March-August 2007, http://blogs.mathworks.com/steve. Requires Image Processing Toolbox. Functions include dem_flow, dependence_map, facet_flow, fill_sinks, flow_matrix, influence_map, pixel_flow, postprocess_plateaus, upslope_area, vis_dem_flow, and vis_map. Includes a sample DEM data set.
Required Products	Image Processing Toolbox
MATLAB release	MATLAB 7.4 (R2007a)
Zip File Content
Other Files	license.txt, upslope/border_nans.m, upslope/Contents.m, upslope/dem_flow.m, upslope/dependence_map.m, upslope/facet_flow.m, upslope/fill_sinks.m, upslope/flow_matrix.m, upslope/influence_map.m, upslope/milford_ma_dem.mat, upslope/pixel_flow.m, upslope/postprocess_plateaus.m, upslope/Readme.txt, upslope/screenshot.jpg, upslope/tests/Readme.txt, upslope/tests/test_border_nans.m, upslope/tests/test_dem_flow.m, upslope/tests/test_dependence_map.m, upslope/tests/test_facet_flow.m, upslope/tests/test_fill_sinks.m, upslope/tests/test_flow_matrix.m, upslope/tests/test_influence_map.m, upslope/tests/test_pixel_flow.m, upslope/tests/test_postprocess_plateaus.m, upslope/tests/test_upslope_area.m, upslope/tests/test_vis_dem_flow.m, upslope/tests/test_vis_map.m, upslope/upslope_area.m, upslope/vis_dem_flow.m, upslope/vis_map.m

Tags for This File
Everyone's Tags	dem, earth sciences, flow direction, hi, hydrology, upslope area, very nice work i tried to make one myself but it didnt work
Tags I've Applied
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Comments and Ratings (5)
19 Aug 2007	Wolfgang Schwanghart	Hi Steve, great contribution! Users of older Matlab versions (R14) need to replace the function hypot(s1,s2) by s = sqrt(abs(s1).^2 + abs(s2).^2) One critique: The functions don't handle NaNs. Best regards, Wolfgang
20 Aug 2007	Steve Eddins	Hi Wolfgang, Do you have opinion about should be done with NaNs? Thanks, Steve
20 Aug 2007	Wolfgang Schwanghart	Hi Steve, areas of interest to geographers often are catchments which commonly have irregular shape. Beyond the watersheds there is often a lack of data. Hence, these values outside the catchment are NaNs. While NaNs inside the catchment may be interpolated the NaNs outside can merely be extrapolated. Hence, I tried following. I replaced the NaNs in the DEM by -Inf. That works except that it produces an erroneous flow direction on the watershed pixels. Best regards, Wolfgang
18 Jul 2008	Felix Hebeler	After implementing Tarbotons Dinf algorithm for calculating flow directions I finally stumpled upon your toolbox, which is a lot faster. Thanks for the implementation, maybe if you add a keyword 'flow direction' it could save some other users some work ;-)
23 Oct 2009	Charlie seviour seviour	How do you combine this script with flow data? If the flow was the same for each pixel I could simply multiple the upslope area by a constant. Since this is not the case I need to find a way of inputting my flow data as it calculates the up slope area. Can anyone enlighten me, Charlie

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Updates
07 Aug 2007	Based on feedback I've received, I removed the "plateau flattening" step from the upslope area computation. This step is now provided as a separate function.
02 Oct 2007	Version 1.2. Alter handling of border-connected NaN pixels based on feedback from Wolfgang and others.
18 Mar 2008	Version 1.3. Corrected border NaN computation for dependence_map and influence_map.
25 Sep 2008	Version 1.4 - modified fill_sinks.m to fill using 8-connectivity instead of 4-connectivity.
02 Oct 2008	Added flow direction keywords as suggested by reviewer Felix. Thanks!
10 Mar 2009	Version 1.4.1 ============= 10-Mar-2009 * Fixed M-file help typo in dependence_map.m. * Allowed input matrix E to contain NaNs in postprocess_plateaus.m. * Added unit test directory.
26 May 2009	Version 1.4.2 - Added sample DEM data source information to Contents.m. No functional changes in this version.
17 Sep 2009	Use assertElementsAlmostEqual in unit tests.

Tag Activity for this File
Tag	Applied By	Date/Time
upslope area	Steve Eddins	22 Oct 2008 09:21:55
hydrology	Steve Eddins	22 Oct 2008 09:21:55
dem	Steve Eddins	22 Oct 2008 09:21:55
earth sciences	Steve Eddins	22 Oct 2008 09:21:55
flow direction	Steve Eddins	23 Oct 2008 10:33:17
hi	Charlie seviour seviour	23 Oct 2009 09:23:03
very nice work i tried to make one myself but it didnt work	Charlie seviour seviour	23 Oct 2009 09:23:03

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