Latest Contributions by MarkBoucher

Luis, How to process your data to analyze drainage patterns is a bit more complex than can be "taught" through a forum. The best I can do for you is to again direct you to the forum at http://forums.arcgis.com/threads/48100-ArcHydro-Problem-Solvers where there are several posts and links about Arc Hydro. Arc Hydro is the ESRI created/supported tool set that uses Spatial Analyst functions to analyze watersheds. It is free to download. The link above contains the information on the ESRI ftp site where you can get the latest version. For the LiDAR data, you will need to convert that to a DEM raster format. The contours could be used to verify the DEM, or if you have locations with contours and not LiDAR or DEM you can use the contours to create rasters. You may have to research each of these conversions. In my understanding, you only need the DEM to run Arc Hydro. You may need a polyline layer for areas where the DEM does not define the flow paths (streams) well. Again, the posts at http://forums.arcgis.com/threads/48100-ArcHydro-Problem-Solvers cover a lot of this though not the LiDAR to DEM conversion or the contour to DEM conversion. ... View more

The answer depends on what kinds of patterns you are looking for. Check out posts in the link in my signature for some posts about Arc Hydro. Arc Hydro uses DEMs. If you have LiDAR or contours, you will need to convert them to DEM format to use Arc Hydro. ... View more

Eric, Understood. It is just that sometimes, when the geoprocessing is not working the way I thought it would, instead of resetting the processing extent and trying the process again, it would help to simply display the processing extent to understand better where I was when the processing didn't work. It would help in the iterative learning I end up doing. Also, I have had some functions in Arc Hydro change the extent without my wanting it to. Then, I'd run in to strange behaviors that I can only explain by blaming some function. This one I could not repeat on that project, but it happened on another one. It might be a handy debug tool also. ... View more

You can limit the area the geoprocessing works on by changing the processing extents. Menu: Geoprocessing>Environments>Processing Extents  and select the layer that defines the area you want to process. This set a rectangular area that fits extents of the features in that layer. The Spatial Analyst tools will only do there work in this extent. There are times when I've experienced the results coming out not not covering my study area. It is often because the extent was defined by some process and was not reset to the extent you want. I use this command to reset the processing extent. You can "clip" the raster you are working on. I use Spatial Analyst Tools.tbx\Extraction\Extract by Mask. This lets you use a polygon as a mask to extract just a portion of a raster you want to analyze. You may need to set the extent as described above anyway. Link to topic:http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Output_Extent/001w00000009000000/ Idea: It would be nice if ESRI created a way to view the processing extent graphically. Right now, I think one can only look at the coordinates in the Processing Extents dialogue box and maybe somewhere else. You'd have to be pretty experienced with your NSEW coordinates or Lat/Long to just look at that and know it is right. (I posted this idea on http://ideas.arcgis.com/) ... View more

I've used the Shift command for this type of thing. In model builder you can automate and trial and error your process. Tool location: Toolboxes\System Toolboxes\Data Management Tools.tbx\Projections and Transformations\Raster\Shift Related post for using Shift: http://forums.arcgis.com/threads/75804-surface-angle-in-each-cardinal-direction?p=265962&viewfull=1#post265962 ... View more

Welcome to the forum! Can we assume that the DEMs cover the same area and that the difference between the two DEMs is the depth of the snow? If so, with Spatial Analyst, 1. You can do raster math subtracting the earth DEM from the snow DEM.[INDENT]Toolboxes\System Toolboxes\Spatial Analyst Tools.tbx\Math\Minus This will give you a depth raster. If the DEM grid cells where there is no snow is the same in both DEMs then the result of the subtraction will be zero. (side note: With the depth raster you can modify the symbology so the zero values have no color and the rest of the values are in a color ramp. You can then visualize the depth) [/INDENT] 2. You may need to run a Con() function to make all the non-zero values one  value such as 1. (Otherwise skip this and go to step 3). You use the Con() function in Raster Calculator or you can use the conditional tool Con.[INDENT]Toolboxes\System Toolboxes\Spatial Analyst Tools.tbx\Map Algebra\Raster Calculator You could alternately use the Conditional tool in Spatial Analyst. Toolboxes\System Toolboxes\Spatial Analyst Tools.tbx\Conditional\Con [/INDENT] 3.  With the raster with zero values where the snow depth is zero and 1 where the snow depth is greater than one, you should be able to convert the raster to polygon or polyline.[INDENT]Toolboxes\System Toolboxes\Conversion Tools.tbx\From Raster\Raster to Polygon or Toolboxes\System Toolboxes\Conversion Tools.tbx\From Raster\Raster to Polyline [/INDENT] ... View more

The Union tool might be what you are looking for. Look under Toolboxes\System Toolboxes\Analysis Tools.tbx\Overlay\Union ... View more

Have you tried the Con() function in the raster calculator? http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Building_expressions_in_Raster_Calculator/009z000000zn000000/ ... View more

I know the installation file for HEC-GeoHMS from the HEC website includes the ApFramework installation for the ArcMap 10.0. I don't know if their installation file for 9.3 includes ApFramework for 9.3. So, if you haven't done so, download the 9.3 version of GeoRAS from the HEC website (http://www.hec.usace.army.mil/software/hec-georas/downloads.aspx) and try to install that. You will likely have to uninstall ApFramework and others before you install the HEC site version. If that doesn't work, you might try the ESRI River Hydrauilics FTP site. This Forum has the web address, username and password. http://forums.arcgis.com/threads/82087-New-password-for-Arc-Hydro-ftp-site?p=289075&viewfull=1#post289075.  Open the folders until you see ApFramework. In there I see a folder named "Setup9.3_9.3.1". That might be what you need. ... View more

Working with rasters over the network is slow. If you can work on them on your local machine, the processing time is greatly improved. This goes for goeprocessing in spatial analyst; where I've experienced it. ... View more

Using Arc Hydro, there is a point in the process where you put in the  number of cells at which streams should start. This is the stream  definition step. Maybe this is the process you need to go through. See  link below my signature for several posts on Arc Hydro. ... View more

Using Arc Hydro, there is a point in the process where you put in the number of cells at which streams should start. This is the stream definition step. Maybe this is the process you need to go through. See link below my signature for several posts on Arc Hydro. ... View more

An attached image instead of an imbedded one. ... View more

I looked closely at Ajay's image. In the upper right portion, there is a stream that goes outside of the watershed boundary. This is likely the problem.  See the attached close up of the spot the creek leaves the boundary. If you modify your boundary to include the stream, things should get better. All your grid data (fdr, rawdem, str, strlnk, etc...) need to be inside the boundary also. I once had a creek that went right up to the edge of a watershed. In the processing creek would end right near the boundary. I think it is because the burning streams lowered the DEM at the boundary and then the flow direction grid naturally choose that as the outlet. The solution was to use an "outer wall". This is likely what is needed here. One problem could be with the "polygon file of [your] actual watershed" (1) .  In the hydrology geoprocessing, nothing is the "actual watershed". The DEM is a discrete grid. If you look close at the streams generated, they go from grid center to grid center. The watershed boundary's do the same. This does not follow the "actual" feature (stream or ridge). So, if you try to superimpose an "actual watershed" on the grid, you need to consider that the polygon you bring in may not line up just right with the DEM. [ATTACH=CONFIG]26070[/ATTACH] (1) This assumes that I understand what your doing with the "actual watershed". Did you load your "actual watershed" just for comparisons, or did you load it to use it in the processing (Batch Watershed Delineation for Watersheds)? ... View more

I would have tried Union. However, reverse-buffer seems more direct. ... View more