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Hi Curtis, thanks for the advice. I've tried to construct a cost surface based on slope, but I haven't been able to figure out how to do it so it takes into account the direction of travel. I need it to do so because there are different costs to going up and to going down a particular slope degree.Is there any way to calculate slope relative to a starting point other than the path distance tool? Thanks again Michal
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04-04-2013
01:57 AM
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Hi all, I've been trying to use the path distance tool (ArcGIS 10) in order to delineate a 2 hour walking distance around archaeological sites. I'm trying to model the calculation in a way that will take into account the changing slope in the area. After consulting the forums and past posts, I'm using the following inputs: 1. a shapefile with the site's location 2. a DEM (floating, 32 bit) of topography, cell size=25m, as a surface raster 3. the same DEM as the vertical factor surface 4. a vertical factor table (created by Nico Tripcevich based on Tobler's hiking function, discussed here http://forums.esri.com/Thread.asp?c=93&f=995&t=138683, among other places). the results I'm getting do not seem to be reasonable; it seems that the DEM has no effect, as I'm getting a very much circular pattern even when a site is located within a steep valley (in such a case I would expect a more elongated radius, following the valley route). I've tried running the tool without the vertical factor, and indeed I'm getting a spider-web-like result, with the cost just increasing with distance in straight lines... this again makes me think that for some reason the tool isn't taking the DEM into account. I've been going almost crazy trying to solve this... any ideas?? I don't know if there's something I'm not doing properly, or if there's a problem with the tool itself... Thanks Michal
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04-03-2013
12:57 PM
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Well, you got it - the problem must have been the extent. It took forever to run (apparently my computer is even slower than yours), but with a restricted extent I did get better results. Now I just have to think how I can double-check the validity of my results... It seems to give a bit too small of a radius. Thank you very much for your help! I appreciate it very much! Michal
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10-31-2012
12:59 AM
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Hallo, Did I get you right ? regards, PS: extent gives a problem I think Hi! Thank you for taking the time to help! You got it exactly right... I don't get what I've done wrong. Are you using ArcMap 10.0? The only thing I can think of is the table - how is yours built? is it saved as a .txt file? everything else is exactly spot-on... Thanks again Michal
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10-28-2012
12:00 AM
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I'm using an ASCII table that includes the slope (in degrees) and a factor (calculated according to hill walking reconstructions), which adds x amount of time cost for up hill walking or for descending down a very steep slope, and subtracts x amount for walking down a moderate slope. It basically has two columns. one with the slope degrees starting with -90 and up to 90 and the other with the appropriate cost. And yes - I am going slowly crazy over this 🙂 I've tried every idea that appeared on the older thread, including transforming the rasters to integers, the source file into a raster and back, etc. everything except magic 🙂 Thanks again Michal
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10-24-2012
11:05 PM
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Hi, I suggest you work with Aspect map (spatial analyst). Hi Srirama, Thank you for your reply! That works well, especially when working with a specific path/direction. I am trying to model catchment areas, or exploitation areas around archaeological sites, so my main interest is in defining walking time parameters (for example, what area is controlled from the site, within 1 hour walking distance). I think path distance tools are perfect for that, as they calculate the cost of moving through the terrain, while taking slope and direction into account. Unfortunately, I've encountered a major problem with the tool, which, according to the thread I found in the forum, has been driving people crazy for over a year now... The tool is basically calculating the cost according to distance, with no regards to the vertical factors I've put in. I'm working with a 5m cell size DEM as the surface raster and an ASCII table for the vertical factor. Here is the thread on the issue http://forums.arcgis.com/threads/23888-Problem-with-DEM-and-Path-Distance?highlight=path+distance any suggestions? Thanks! Michal
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10-24-2012
06:55 AM
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You were right! Path distance is the way to go, and I've finally figured out how my data needs to be stored to use as input... However, I've encountered a new issue - I keep getting a "spider-web" type raster, where the cost just increases with distance, with no regards to the other factors. I'm using a 5m cell size DEM as the surface raster, and a ASCII table with the vertical factor. I found a very long thread, dealing with the exact same problem: http://forums.arcgis.com/threads/23888-Problem-with-DEM-and-Path-Distance?highlight=path+distance I'm not sure whether this makes me feel better or worse, but I was wondering if you had any ideas?? Thanks Michal
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10-24-2012
03:03 AM
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Hi everyone! I'm not sure if seeing such a long thread about the same problem I'm having makes me feel better or worse... I'm trying to calculate path distance travel time, using a 5m cell size DEM as the surface raster, and a ASCII table with the vertical factor. I keep getting this Eucledean "spider web" type raster... Any suggestions? Has anyone been able to solve this issue? It is driving me INSANE... Thanks Michal
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10-24-2012
02:57 AM
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Hi Dan, thanks for the quick reply... I've tried using these, however, the "path distance" requires an existing cost surface. As for the path distance allocation tool, I couldn't find where the actual factors should be entered (i.e. the conditions that transform a certain slope to time costs). Any suggestions? Michal
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10-22-2012
09:09 AM
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Hi, I'm trying to create a cost surface for hill walking time expenditure, based on slope and distance. To do so, I need to know whether at a specific cell the slope is positive (= walking uphill) or negative (= walking downhill). Any ideas? Thanks Michal
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10-22-2012
06:12 AM
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