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Same in Germany, changing the decimal symbol helped... thanks.
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02-21-2015
01:47 PM
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Your interpretation of the Con statement is incorrect. A conditional statement takes the form: IF, THEN, ELSE. Using ArcToolbox > Spatial Analyst Tools > Map Algebra > Raster Calculator, it should look like this: Con("arroyo_h" == 0, "vcf_tree", (("vcf_tree" / 100) * 0.6) * "arroyo_h") Translation: IF: "arroyo_h" == 0 THEN: assign value from "vcf_tree" ELSE: (("vcf_tree" / 100) * 0.6) * "arroyo_h" It looks like your rasters are floating point. The default resampling method, performed on the fly, is nearest neighbor. This is not appropriate for floating point rasters and will yield undesirable results. I would recommend resampling your rasters to a consistent resolution prior to analysis. You can find the Resample tool under: Data Management Tools > Raster > Raster Processing > Resample. Under the "Resampling Technique" drop-down select "BILINEAR". Thanks, this works now, but i use: Con("vcf_tree" == 0, "arroyo_h", (("vcf_tree" / 100) * 0.6) * "arroyo_h") since arroyo_h contains the values that should be changed by vcf_tree or stay unchanged if vcf_tree == 0. But my first results show me that i have to change some things.. 🙂 Of course i tried to build my equation considering the syntax from the help @Stevelynch, but i think this is quite confusing. I did some programming in university, so i know how conditional statements work. The problem is that i still don't understand what the {where clause} is for? And the example from the help (OutRas = Con(InRas1, 40, 30, "Value >= 2")) kind of represents what i tried in my second post, or am i wrong? Actually the arroyo_h raster is floating point, the vcf_tree is 8bit unsigned (i think nearest neighbor was the right choice when i reprojected this?), where 0-100 is the percentage of tree coverage, 253 is water (which i still have to filter out of this). Anyways, THANK YOU!
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10-09-2012
11:46 PM
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Thanks for your help! I had to change a few things (i think?) because no expression was allowed for the first parameter.. and i think you have to put the condition into the {where clause}? But it still doesn't work, i even put the vcf_tree raster into my .gdb (which was even weirder.. better don't use "." >8 characters as filename..grr) and now i use this expression: Con("vcf_tree",(("vcf_tree" / 100) * 0.6) * "arroyo_h","arroyo_h","Value" > 0) also tried Con("vcf_tree",(("vcf_tree" / 100) * 0.6) * "arroyo_h","arroyo_h","vcf_tree" > 0) But i get this everytime: ERROR 000539: Error running expression: rcexec() <class 'arcgisscripting.ExecuteError'>: ERROR 010416: Error in setting raster table filter for E:\Documents\ArcGIS\Analyse\analyse.gdb\vcf_tree. Failed to execute (Con). Failed to execute (RasterCalculator). Also both rasters are in different resolution, and i want to use "Minimum of inputs" as cell size. PS.: Further explanation: i try to change a cost-raster (which contains walking time in hours per cell) by the vegetation index (MODIS VCF).
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10-09-2012
01:11 PM
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Hi, this is a little embarassing but i have the following problem, and i'm sure there's a very simple solution: I want to multiply the values of 2 rasters, using one of them as a factor to reduce the values of the first raster. The problem is, the cells of the second raster contains 0, which, of course, results in 0 in the output-raster, which is wrong. 🙂 I want the Raster Calculator to do just nothing if this case occurs. I hope someone can help me! My calculation looks something like that: (("second_raster.tif") * 0.6) * "first_raster"
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10-09-2012
10:32 AM
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I've been trying to run the Path Allocation tool with a custom VRMA-VF table to model energy expenditure for travel on foot. The tool will run if I use the built-in vertical factor functions, but hangs indefinitely (most common in ArcGIS 10) or fails with a meaningless error message (most common in ArcGIS 9.3.1) when I use a custom table. I assume I have made an error in formatting the table. The online help (http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//009z000000z9000000.htm) gives an example for building the table, but it is just a copy of the sample table for the horizontal factor. Does vertical factor also need to run from 0 to 180 degrees? If so, to what slope do 0, 90, and 180 correspond? Concerning this i just experimented with the table until ArcGis stopped crashing... I think it doesn't matter if there are Tabs or Spaces between the VRMA and the VF. What worked was, leaving the smaller intervals below/above -70 and 70 away.. so Doesn't work: ... -73 13.11118151 -72 6.668357861 -71 3.633583399 -70 2.099401323 -69 1.275442246 ... Works: -90 -1 -80 -1 -70 2.099401323 -69 1.275442246 I also tried to change the VFs higher than 3 to -1 without leaving the other VRMAs away.. didn't help either. 😉
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07-12-2012
02:40 AM
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Hmm, well i was a little imprecise there, by extent i of course "meant" the cell-count, i think something around 200.000 pixels may be the threshold. You even see it if the tool starts, when it works, you can see the numbers "counting" in the processing-window. I assume you used elevation-models bigger than that?! i also tested with a esri-grid 8bit signed int file, no differences and i resampled the raster to a lower resolution with the solution that the working extent grows.. 🙂 the only idea i have right now is to test this on another windows, maybe a non-x64 one.. but i think i should continue this in the other thread, i hope this will get a bit more attention. 🙂
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07-11-2012
10:19 AM
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Hmm okay did you actually get it to work on a really huge raster? Mine has a cell size of 10m and is about.. well.. more than 20x30km.
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07-11-2012
01:17 AM
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Hi, i'm experimenting with this myself.. the whole day again.. i also have crashes with both "versions" of the tobler.txt (with spaces or tabs). the other thing is that the path distance tool seems to be very picky in regards of the elevation raster (and i couldn't really find anything about that in the documentation) I have a 10m DEM, i tried .tif or converted it to ESRI GRID (32bit floating point i think), most of the times i get results mentioned in this thread http://forums.arcgis.com/threads/23888-Problem-with-DEM-and-Path-Distance or it crashes. It only seems to work if i use a very small extent. That's all quite bad, since i think it would be the perfect tool for my diploma-thesis. 😞
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07-10-2012
09:25 AM
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I think this thread can be closed, i now know better how Path Distance works (if it does.. :)) and somehow can't edit or delete it myself?
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07-05-2012
01:59 AM
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Ohh.. same problem here. I work on my geography diploma thesis which is about, well.. prehistoric sites and distance/site catchment analysis around caves (and i have to work with arcgis). Now i discovered the toblerAway-table and was very happy that this could be a nice solution, but it only works if i zoom in to a very small extent (while using processing-extent: same as display). In other cases i also get the Euclidean Distance pattern in the resulting cost raster. 😞
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07-05-2012
01:55 AM
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Hi, i'm just at the beginning of my diploma-thesis which has to do with walking-routes in hilly terrain based on dem-analysis and other data.. i stumbled over the cost-path tool. Since i still can't really get my head around the whole topic (i think i kind of have to implement Naismith/Langmuir or Tobler's rules for walking costs with arcmap/spatial analyst by weighted distance analysis..) i'd like to know if it's legitimate to use the outcome of the path distance tool for a cost path analysis? Maybe this is the completely wrong way.. so i'd appreciate it if someone tells me that before i waste many hours with trying. 🙂 Thanks in advance and i think i will post more often in the next time, while working on the thesis. 😉 Daniel EDIT: Oh and, maybe a hint to a little tutorial/workflow for the Path Distance tool would be nice. The Esri-Course for Distance Analysis helped me a lot with the Cost Distance tool, but i couldn't find any equivalent for the Path Distance tool.
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06-22-2012
05:56 AM
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