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README FILE FOR "ISOLATE GLACIERS" ALGORITHM
William Manley, University of Colorado, 3 October, 2002
This file describes several "scripts" or semi-automated algorithms submitted to the GLIMS program for identification of ice divides and creation of "glacier" polygons separate from "ice polygons" (vector layers of large, inter-connected ice masses). The scripts inherently establish a quantitative, objective definition for the term "glacier". Hopefully a common and widely accepted approach such as this could be established for uniform comparison of glacier properties.
Please note: these algorithms are contributed to the GLIMS effort, but were developed for an NSF-funded study on spatial analysis of glacier-climate relationships across Alaska. The scripts were written for use in ArcInfo and ArcMap, v. 8x on Windows 2000 and XP. I have not edited the scripts to tailor the processing to GLIMS objectives. Use the scripts at your own risk. They are commented thoroughly, and hopefully will be self-explanatory. Modify as need be for your own purposes. The scripts appear to work well for 1:63,360-scale ice polygon coverages and co-registered 60 m DEM's for Alaska. For further information about this and other projects, see: http://instaar.colorado.edu/QGISL.
Inside this folder, you will find several files:
mmm185_hyd_sound_dem_v2.txt mmm190_ice_grids_v4.txt mmm195_isolate_glcrs_v4.txt mmm200_delete_items_v1.txt mmm205_edit_glcr_frags_1.jpg mmm205_edit_glcr_frags_2.jpg mmm205_edit_glcr_frags_v1.txt mmm210_edit_hanging.jpg mmm210_edit_hanging_v3.txt
yyy_dem, the DEM for the area of interest
yyy_ice, a polygon coverage of inter-connected ice masses (each userID attribute should be unique)
yyy_dem_hs, a depressionless DEM
yyy_flowdir, a flow direction grid
yyy_gl_uned, glacier polygons prior to minor editing for "fragments" and hanging glaciers
t_gl_ed88, the edited glacier coverage prior to final review for quality control various other intermediate polygon coverages and grids
Move sequentially through the scripts. If you find them helpful, or if you have suggested improvements, I'd appreciate hearing from you.
There are no publications yet on the processing or related research results. The scripts can be informally cited as: Manley, W.F., 2002, GIS algorithms for identification of ice divides and glacier boundaries from complex ice masses: INSTAAR, University of Colorado, unpublished.