Latest Contributions by MarkBoucher

Also, check your processing extents. Go to Geoprocessing>Environments>Processing Extent and set the extents. ... View more

If you put the data in a geodatabase you can create a topology and use topology rules and tools to clean up these problems with much less effort and much more accuracy than manually editing them. That would be worth looking into. Topology rules such as "must not overlap" and "must not have gaps" will identify the gaps and overlaps and topology tools allow you to remove the overlaps (choose which feature they really belong to) and fill in the gaps (again, choose which feature they belong to). ... View more

New password for Arc Hydro ftp site http://forums.arcgis.com/threads/82087-New-password-for-Arc-Hydro-ftp-site ... View more

Use the Intersect Tool with Shapefile 1 and Shapefile 2. You will get a new shapefile that includes shapes only where they intersect and the fields of both in the table. Then find the field that represents Shapefile 1 and use the Dissolve  tool (Data Management Tools.tbx\Generalization\Dissolve) with that field. This will result in polygons that are dissolved to represent the Shapefile 1 areas only where they overlapped Shapefile 2. If these are outside of a geodatabase, you will have to recalculate the Shape_Area field or create an Area field and calculate the area. You might get the same results using the Analysis Tools.tbx\Extract\Clip tool. ... View more

Try the batch points and do a watershed delineation. It should create watersheds that overlap  and just one per point. Don't forget to change the BatchDone field in the Batchpoints to zero. If you don't, Arc Hydro or GeoHMS will see them as done and won't use them. ... View more

I did finish the tool I was working on. The tool is faster than the individual polygon solution.  Originally I produced 3 different solutions for breaking up the polygons and ended up using two of those methods.  I have uploaded the tool and documented it. The tool uses Spatial Join and also breaks up the feature class into smaller pieces. http://www.arcgis.com/home/item.html?id=b859b33c616a47d2b99b5e133942db02 Every one of my polygons overlap at least one other polygon. Will this tool work for me? Basically, every polygon would have to be process separately, correct? The grouping technique would not work. ... View more

I recall from my past work, that the surveyors doing aerial stereographic topography had specific limits on the precision (minimum vertical interval of contours) they could create in topographic maps that were paper/mylar and later CAD. These were used by Civil Engineers doing land development. If the engineer needed better accuracy, s/he would send a survey crew out to shots with a rod. The question might be better posed to surveyors on http://forums.arcgis.com/forums/105-Survey-Analyst (though I'm not sure you would be asking about that extention). You could also look for articles like this one that I found: http://www.csc.noaa.gov/digitalcoast/geozone/lidar-accuracy-versus-resolution ... View more

You may want to increase the raster size Arc Map will deal with. See here including the link in the post. http://forums.arcgis.com/threads/23888-Problem-with-DEM-and-Path-Distance?p=247771&viewfull=1#post247771 ... View more

Sorry to hear you are having problems. One other thing I've done that seem to have greatly reduced the crashed (and tears) is to copy the project to my local PC and not have it on the network. My suspicion is that using Spatial Analysis and geoprocessing over a network takes a lot more time and introduces more chances of errors as the data goes back and forth through the routers. I can't verify this since my understanding of networks and routers is limited. So, if you are trying to work on rasters and datasets over a network, copy them all to a folder on your PC and try to make it work then. I can guarantee things will go much faster and can almost guarantee you'll have fewer processing crashes. An easy want to do this, if the files are all in one folder on the network, is to choose the option under the "File" menu for the mxd properties and make the references to layers "relative" (I think. I can't check now b/c my Arc Map is busy). Then after you copy it all to your PC you don't have to remap the layer sources. ... View more

I tried my suggested method and am having problems with step 4. To get there I let the thing run past work hours. As I was cleaning up the bazillion temp files/folders, I noticed on folder was time stamped near midnight. There was over 700,000 MB of temp files to delete. The GeoHMS "Parameters from Raster" function for step 4 only calculated the aggregate value for 1 or 2 out of 5 of the watersheds. Same problem with Zonal Statistic trials. However, I just found this recent post and downloaded the script (the one posted at 08-09-2011 08:59 AM by Jaimie - I edited the script to look for the OID instead of the FID since my feature class did not have an FID): http://forums.arcgis.com/threads/36799-Zonal-Statistics-as-Table-Overlapping-Polygons-Solution-Required?p=124309&viewfull=1#post124309.  It seems to be working as it is supposed to, but I suspect it will take a while since I had nearly 6000 grid points on the stm layer => nearly 6000 polygons in the watershed layer. Will report back when it finishes (or not). ... View more

As far as I know, Arc Hydro has always been free. It does require Spatial Analyst. ... View more

Using existing Arc Map/Arc Hydro/HEC-GeoHMS tools, I can see how to do it, but it seems it would take an immense amount of processing time. I can't quite picture is how to limit the aggregation to the nearest upstream 5000 cells. I think maybe some python script would be needed to make that happen. Maybe some special third party tool has already been created to do this. Here's what process I can envision for doing this without the 5000 upstream cell limit: Convert str (stream) raster to points. This results in one point per cell of the str raster. Import the created points to BatchPoint layer (for Arc Hydro processing). You need to have processed the terrain and created all the Arc Hydro layers/rasters. (a tool in GeoHMS will import points to the BatchPoint layer by creating the layer with all the required fields) Process the watershed delineation using the batch points. This makes one watershed polygon per point and they will overlap. This would take a very long time and may tax the memory limits of the processing. Processing this on the local machine and not over a network would be a must. Use GeoHMS tools to aggregate the watershed parameters to the polygons. Use relate tools to bring aggregated parameters back to the points. Convert the points back to a raster using the parameter. To get to the "nearest upstream 5000 cells" you might be able to perform the above steps and then find a way to select a watershed and then find a watershed upstream that you could extract that would provide a value base on limited upstream proximity. Again, python or other programming might in order to do this. ... View more

Tomasz, Have you had trouble making the Arc Hydro functions work with the floating point DEM? As for the Sink functions: Sink Evaluation help says the input DEM being evaluated for sinks should have linear and z units explicitly set. If the z unit is not set, the tool will assumes that the z-unit is the same as the linear unit. It does not seem to me that it would require any changes to the DEM if the DEM raster has the same units in horizontal and vertical directions. Basically, the assumption is the z-unit has the same units as the x, y unless the data indicates otherwise. Sink Pre Screening help does not mention anything about the z-unit Sink Selection does not require the DEM. Sink Watershed Delineation does not require the DEM. If you can explain what you are trying to do with the sinks and the sink functions or share your data, maybe I can help you more. If I were you, I'd try to run the processes with the DEM you have. The problems you have, if nay, may not be related to the z-unit or the integer/floating point issues. ... View more

You may want to consider further defining what you want. You need to decide if you want the accumulation to be at every cell in the raster (not likely what you want), every cell on the stream, at regular intervals along the stream, specific points of your choosing, or at confluences. If you want to do the latter, you could use the number of cells variable in the Stream Definition step to "granularize" the number of points/confluence you get along the streams. You could use the stream order function to eliminate minor streams if you don't want points on every little tributary. If you come up with a way to do this from a point, then you can convert your stream raster to points and geoprocess this for every point on the stream. ... View more

I wanted to try and change the pixel values to make my raster act like there wasn't a road crossing the river. This is exactly what Arc Hydro does when it "burns in" streams. You can do this manually. Its a bit of work if you just need to lower a few pixels... Basically, to mimic Arc Hydro, you could make a stream polyline feature class and draw a line segment along the stream through the crossing. In a field for that line, put in a number for adjusting the DEM elevation. Then convert the line to a raster using the adjustment value. Then add or subtract the two rasters and you will lower the DEM elevation. (I think you could do the same thing for a point.) In Arc Hydro the next steps include filling sinks. If the line elevation was too low to match the lower end flow line, filling the sinks in the DEM will raise the elevation to match the downstream DEM grid elevation. A fill sinks function will also fill other sinks in your DEM, so if you just want to make a local change, you would have to play around with the processing extents for the fill function and then mosaic the result back into the original DEM. Running fill sinks and then subtracting the original DEM from the filled DEM is a good way to find other places where you might have road crossings "blocking" your streams. ... View more