/* EDIT HANGING GLACIERS template script: mmm210_edit_hanging_v3.txt template script last modified 8/14/02 by Bill 1) save this script with a new name: yyy210_edit_hanging_v3.txt. This script modified and run xx/xx/xx by xxxxx. You just edited the glacier coverage for one type of artifact, glacier fragments. Now you'll edit the glacier coverage, focusing on "hanging glaciers", those small ice masses near the headwalls or steep sidewalls, perched above main trunk glaciers, onto which they shed ice. Though physically separate from the trunk glaciers, the hanging glaciers contribute mass to the trunk glacier. Without associating hanging glaciers to the trunk glaciers, using the same "ID" number, they would provide spurious ELA estimates. BTW, if we ever want to keep track of the hanging glaciers and other glaciers separately, we can use the "pound" number for the glacier polygons. So, with this script, and some judgement, you'll associate hanging glaciers with corresponding trunk glaciers. NEEDED: t_gl_ed01, the glacier coverage previously corrected for fragments yyy_dem CREATED: t_gl_ed02, a glacier coverage with hanging glaciers associated with trunk glaciers through a common "-ID" value. t_glcr_m1 t_glcr_id_all t_glcr_id t_glcr_median t_glcr_id_ed t_glcr_id2 t_glcr_med2 t_gl_ed88, the edited glacier coverage CREATE A FRESH COPY TO WORK ON 2) Start Arc, and: w ../modern/yyy &watch yyy_yymmdd.txt &append &format 6 precision double highest lc lg 3) At the arc prompt, type: copy t_gl_ed01 t_gl_ed02 CREATE A MEDIAN ELEVATION GRID In the next several steps, we'll create a grid depicting the median elevation for each glacier. This will help to identify hanging glaciers. The median elevation is a very rough measure of ELA. Though somewhat circular, it does a better job of anything else at suggesting which glaciers are hanging. 4) start grid 5) this step converts the glacier polygon coverage to a grid, with grid cells coded to minor1. At the grid prompt, type (or copy and paste): t_glcr_m1 = polygrid(t_gl_ed02, minor1, #, #, 60) 6) next we'll create a grid coded to "-ID" value. At the grid prompt, type (or copy and paste): t_glcr_id_all = polygrid(t_gl_ed02, t_gl_ed02-id, #, #, 60) 7) now we need to isolate glacier grid cells, using a conditional statement. At the grid prompt, type (or copy and paste): t_glcr_id = con(t_glcr_m1 == 103, t_glcr_id_all) This says: If the grid cell has a minor1 value of 103, assign it the value in the id_all grid, otherwise make it NODATA. 8) Now we'll calculate the median elevation for each glacier. At the grid prompt, type (or copy and paste): t_glcr_median = zonalmedian(t_glcr_id, yyy_dem, data) START ARC MAP 9) Start ArcMap, add t_glcr_median, and change it's symbology: switch color ramp to red-to-blue invert ok Wow. This is our first glimpse, roughly, of ELA patterns in the area. Blue is low (closer to ppt source, sheltered), red is high (in rain shadow, maybe south facing, ...). Is there a trend? Is there signal? 10) Add t_gl_ed02, and change it's symbology: categories unique values minor1 add all uncheck "all other values" remove 0 make 103 hollow, with a black border with width of 2 ok Now you should be able to see the median elevation colors underneath and within the polygon outlines. 11) add yyy_shaded, and move it to the bottom of the stack. 12) change the transparency for all of the layers to something like 30% IDENTIFYING HANGING GLACIERS Next you'll zoom in, and find a hanging glacier. Some guidelines: look for red or dark orange glaciers lying above but close to green or blue glaciers ... if it's a hanging glacier, the span between it and the trunk glacier should be short and steep in questionable cases, you might want to view the DRG underneath view the example image of a hanging glacier, mmm210_edit_hanging.jpg. The small red glacier in upper center is clearly hanging -- anomalously high median elevation, at top of a steep cirque wall, a short distance from the trunk glacier. while editing hanging glaciers, we want to be conservative -- if any are questionable, leave them the way they are. you might want to make a slope grid using the Spatial Analyst toolbar to highlight areas that are steep if uncertain, ask Bill. EDIT HANGING GLACIERS 13) Open the attribute table for t_gl_ed02, and: show selected make it wide but skinny from top to bottom move it so it's always handy 14) Start editing, and: make sure the target is t_gl_ed02 15) Once you've found a hanging: use the "select feature" tool and click once on the TRUNK glacier click once in the table on "T_GL_ED02-ID", the "-ID" value mentally take quick note of the number right click, copy click once on the hanging glacier click once on it's "-ID" value right click, paste make a mental quick check that it is now the same number VOILA! You have just associated the hanging glacier with it's trunk glacier. Please take your time and be careful when copying and pasting values. 16) Continue to systematically move about the map, editing hanging glaciers. 17) Remember to periodically save edits. 18) When done: clear selected features stop editing save edits close the attribute table UPDATE THE MEDIAN ELEVATION Now we'll create a new median elevation grid. 19) At the grid prompt, type (or copy and paste): t_glcr_id_ed = polygrid(t_gl_ed02, t_gl_ed02-id, #, #, 60) 20) At the grid prompt, type (or copy and paste): t_glcr_id2 = con(t_glcr_m1 == 103, t_glcr_id_ed) 21) At the grid prompt, type (or copy and paste): t_glcr_med2 = zonalmedian(t_glcr_id2, yyy_dem, data) DOUBLE CHECKING 22) In ArcMap: remove the t_glcr_median grid add the t_glcr_med2 grid change it's symbology: switch color ramp to red-to-blue invert ok 23) Systematically navigate through the map again, carefully, and: double check for hanging glaciers if need be start editing again, etc. click on the trunk glacier, copy it's "-ID" value, and paste that into the hanging glacier's "-ID" value. stop editing save edits SAVING THE FINAL GLACIERS 24) Quit out of grid 25) Quit ArcMap 26) At the arc prompt, type: copy t_gl_ed02 t_gl_ed88 WHEN ALL DONE 27) Quit out of arc. 28) Backup (ask Bill) 29) In ArcCatalog, select and delete the following: (*** But don't delete t_gl_ed88 ***) t_gl_ed02 t_glcr_id t_glcr_id2 t_glcr_id_all t_glcr_id_ed t_glcr_m1 t_glcr_med2 t_glcr_median Done. /* ----------- NOTES ------------- Write below any comments you have on unusual or unexpected steps, errors, etc. Include any questions that you might have for Bill. */