Latest Contributions by MarkBoucher

New password for Arc Hydro ftp site - October 1st 2013 ... View more

I tried using the SA Hydrology tools and Raster Calculator to do what you are doing. When I converted the stream polylines to raster I got a single cell pattern for the streams raster. I was not able to get all the tools to give me results I was expecting and then someone else doing "real work" needed the SA license and I had to stop investigating. For your stream raster, you may need a value of greater than 1 to make the burn work. Use the Con() function to create another stream raster where 1 is changed to -1000, then add the two rasters. This will definitely burn the streams deep. ... View more

Sara, I would try the intersect tool. When you intersect a polygon (watershed) feature class and a polyline (streams) feature class the result should be a polyline feature class with an attribute table with fields from both feature classes. From that you could do statistics on the attribute fields to get different information about how many streams are in watersheds. This is a general GIS process and not necessarily an Arc Hydro process. ... View more

Cell statistics compares the value of the cell it is processing with other layers values in the same location. By using and shift function, you can place the surrounding 8 cells "under" the center cell and do some comparisons that you couldn't do otherwise. For example, if you wanted to know if the grid (pixel) were isolated and surrounded by cells that all had the same value, you could use con() to test if the values of the surrounding cells all equaled their average and if the cell had a different value than the average. I'm sure there are other SA functions that could do this or something like it more eloquently. If not, this might be a way to attack the problems. Cheers! ... View more

It says that the input is not in the defined domain and I'm not sure what that means. When I hear "domain" I think coordinate system. My guess is that the raster/layer you are working with does not have a define spatial reference (coordinate system). Go to the layer properties see if it has a defined spatial reference. If not, find out from a colleague what coordinate system you should be working in and set it at that. Also, check the properties of your dataframe and make sure it has a defined spatial reference. Also, sometimes certain functions/tools don't seem to work unless you save the mxd. ... View more

I've used the Shift tool to do things I couldn't find a specific tool for. Here is a similar post I responded to.http://forums.arcgis.com/threads/78067-how-can-I-eliminate-quot-island-quot-raster-cells-from-a-layer.  My post regarding the use of the shift tool is #4. ... View more

I think the processing extent is a rectangle. If you give it a mask with a non-rectangular feature, it will set processing extent  using the extreme North-South-East-West coordinates of the envelope that contains the feature. When I've gotten results where the processing extent was somehow set smaller than I wanted, the results were always withing a rectangular "envelope" with N-S-E-W limits. I think to eliminate the data outside, you actually have to use the mask to clip the data or extract by mask. Depending on what you are doing, you may still need to deal with results outside of the data that is left over after the clip or extract. ... View more

If you use the Stream Link tool you should get a raster with just a stream defined by single grid cells (one cell wide). See example attached. Your image looks like the stream is defined by several cells wide. Your image is not an example of what I would call "parallel streams". In my image, if you look at the confluence to the right of the center of the image, you will see parallel streams defined for a short distance (mine is a 10'x10' grid). They are only one cell apart. If I were to redo this one, I would add agreestream features to burn the DEM so the parallel streams merge (that is if I knew they should not be parallel and should come together sooner). ... View more

happyfjy, I've learned a bit since posting my original frustrations. You can find a link below my signature where I've been posting solutions for a while.  My first gut reaction to your error is that possibly your target locations need to be reset or your file path and file name are too long. Make me wish I had kept a log of the error messages and solutions I found. ... View more

I normally use Arc Hydro that has several handy tools. You can use the Spatial Analyst (SA) tools but the process is not as well set up for someone doing it just once. This is a good link to review if you are using the SA tools. http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Understanding_drainage_systems/009z0000005m000000/ This link http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Deriving_runoff_characteristics/009z0000005p000000/ is a sub-section of the one above and shows a good flow chart of the process. You can force the drainage lines to be at our polylines by "burning" them into the DEM (raster). You can do this by converting the polylines to a raster with a very low number (say -1000). Then add the DEM to the stream raster. The result is a DEM with the streams obviously below the surrounding terrain. Then you can run the fill tool and then the flow direction tool and this will set you up to create the stream features to which you can add the stream order because our flow direction grid will match the streams. Arc Hydro adds a "buffer" the stream burning to ensure that the cells near the burned stream are lowered and you don't get parallel streams right next to the stream defined by your stream polyline based raster. This can happen if the polyline does not line up with the stream in the DEM. I'm sure you could figure out a way to lower the cells around the stream. Possibly you could create a small buffer around your stream polylines and then convert that to a raster with a smaller low number (-100). Then add the buffer based raster to the DEM and THEN the polyline based raster to that resulting DEM. This would take care of some parallel streams. Some of this process will be influenced by the size of your DEM raster cells. If they are large, I don't think you will have many parallel streams. If the grid is small, you could have more. Hope this isn't to confusing. Best, ... View more

Should I be using the lidar data as the raw DEM instead of the flow direction or flow accumulation grids? Do I need to specify file type? The LiDAR data (points, I assume) must be converted to raster data. The rawdem is a raster file not a point file. My experience is most polyline data fails to always follow the creek/river/stream (stream) idenditified via raster DEMs. This is because they are likely created by tracing over old maps that inaccuratly depict the streams or over ariel photos where the stream is hidden by trees.  So, I use the raster with Arc Hydro to determine where the creeks are w/o the streams layer. Then I correct that where there stream is vauge in the DEM and where there are bridges/culverts, etc. that "mask" the creeks. This is where I burn in stream with the DEM reconditioning. I suppose if you wanted to keep your stream polyline layer, you could do the Arc Hydro process create the stream order field inthe drainage layer and then transfer the stream order to your stream polyline layer. ... View more

Sara, In my experience, when I start a new mxd and load the rawdem, agreestream and other layers and then save and start the Arc Hydro processes (DEM Reconditioning, etc.), the target locations are automatically set correctly and things go smoothly. (I believe you must save first before Arc Hydro will work correctly, otherwise I don't think Arc Hydro will know where to put the target locations.) If I do that, I find no need to mess with the target locations. It is only when I'm saving the mxd under a different name and/or directory that the target locations need to be reset. There have been times when I've reset them just to make sure they are correct. Mark ... View more

Sara, Sorry you are having problems. That error look very familiar, but I don't have any specific suggestion on how to get around it. One other step is to start a new mxd and reload the basic layers into that and try again. The other is to make sure you have the right version of Arc Hydro for your version of Arc Map. Sorry I'm not much more help. Mark ... View more

Stein, The graphical location of a stream will not always match the grid of the DEM. There are some "pre-fill sinks" steps that would fix this if you needed to. They are under the Terrain Processing>DEM Manipulation menu. DEM Reconditioning: In this step you choose a layer for the river (streams) and "burn" them into the DEM. Build Walls: In some cases the DEM is so flat it does not adequately define the terrain and will not give you the correct flow direction (the flow direction (fdr) grid is the basis of a good hydrologically correct DEM). You may not need to build walls in every situation. Just like the DEM Reconditioning burns stream (lowers the elevation of the DEM cells), the build walls function raises the elevation of the DEM cells. The rivers in your attachment look like polygons. You would need to create a polyline equivalent and use that. You only need to add polylines for the river locations where the DEM is "confused" about where the stream/river is. After the streams/rivers are burned into the DEM, and therefore the DEM is lowered (could be as much as 1000 feet), the fill sinks function fills them back up to match the elevation of the downstream grid. After the fill sinks step, the river/stream is well defined in the DEM and your stream connections should look right. I always call the polyline layer agreestream since this is the Arc Hydro default and in most cases the Arc Hydro tools will automatically fill in that layer in the tools' dialogue boxes. Hope this helps. See the link below my signature for a forum thread I established just for Arc Hydro problems solving. ... View more