Latest Contributions by DavidWampler

Are there any regions where you have to worry about low-elevation basins in your landscape that aren't connected to the ocean (such as Death Valley in the U.S.? Assuming not, the Raster Calculator in Spatial Analyst -> Map Algebra does a fine job with tasks like this. The statement would look something like: "DEM_Raster"<=2 This will test the boolean statement at each cell of your DEM (is the value within the cell less than or equal to 2 meters). If true, then the output cell at that location will have a value of '1'. If false, the output cell will have a value of '0'. Alternatively, if you don't care about retaining raster cells with values of '0' (those that are above your potential inundation from sea-level rise), then you can use a command like" SetNull("DEM_Raster">2, "DEM_Raster") This will give you a new DEM, where only cells below 2 meters in elevation are kept (all other cells are ignored - they become 'no data'). Or, alternatively... SetNull("DEM_Raster">2, 1) Which will do the same thing as the previous statement, only instead of maintaining the elevation value within each cell below 2 meters in elevation, it will just give them a value of 1. If you only care about area of inundation, then this may be simpler than keeping elevation values in your cells you won't use again. What command you use exactly will depend on what data you have and what you plan to do with the data you produce. You should have plenty of options available to you in Raster Calculator though. Read more about the tool here: http://help.arcgis.com/en/arcgisdesktop/10.0/help../index.html#//009z000000z7000000.htm http://help.arcgis.com/en/arcgisdesktop/10.0/help../index.html#//009z000000zn000000.htm ... View more

Thanks for the help - that got me on the right track. A second difficulty is that the projection I am using is not in the default list (MODIS Sinusoidal) - I should have mentioned that to start with. But, adding a custom geographic transformation for that did the trick. In the end, I got the cell sizes to match up perfectly! For reference of anyone else needing to project into the MODIS sinusoidal, this page gave the required extra information: https://code.env.duke.edu/projects/mget/wiki/SinusoidalMODIS Although I only needed to follow a few of the steps there along with what was mentioned in this thread to get it to work. ... View more

Would they hydrology tool set help?  If you find the divided (watershed boundaries) in the dataset wouldn't that be the ridge you are looking for? Otherwise, I have to think longer.  Please also look at my question for today. Please! Thanks Unfortunately, due to the nature of the DEM I have, establishing pour points would be an extensive process. This was actually the first thing I tried to do : ). Sorry, I can't help you with your question. I'll think about it some, but it's not something I have done before. ... View more

Thanks for the response, but this does not particularly help me - the range crest varies by enough that in order to use a color ramp to isolate the ridge crest I would have to be constantly adjusting it every few dozen meters in some cases. Which is exactly the sort of time-consuming, prone-to-error approach I'm trying to avoid. Converting to points also doesn't help - although it may open up some analysis options. I'm looking for a way to automatically extract the highest points in elevation of a DEM orthogonal to an arbitrary line I draw. If I create a massive array of points, the only way I could do this (that I can think of) would be to manually delete points until I am left with a set of points that represent the highest orthogonal value. Which seems extremely time-consuming too. In plain English, the tool I am looking for would do something like this: 1) Take input of a polyline/line 2) Start at one end of the line 3) Look orthogonally to it in both directions - find the highest value from the DEM layer 4) Assign this value to a point/cell on this line 5) Move one cell along the line and repeat This would easily find the elevation of the ridge crest, which is all I really need. I'm not sure if the capacity to do this exists in ArcMAP though. ... View more