Latest Contributions by DarleneWilcox

‎03-01-2019

I tried this, and did indeed get individual point features, but not all the attributes associated with each feature in the LAS dataset -- the PointSrcID, the GPSTime, the Return, etc. Is there a way to do this? Thanks, Darlene

‎09-08-2016

Neil Ayres ... you rock! That worked -- yeah! Do you know where (other than right here!) this is documented? -- no joke when I say I spent all day yesterday trying every thing I could think of and searching all over the forums and stack exchange and so on. Again -- THANK YOU!!!!!

‎09-08-2016

Dan, I know I need to use the extent -- I just can't get the arcpy.Clip_management command to accept the extent in the rectangle argument! Of course I can enter it manually -- I need to do it within a script. It is a formatting thing -- how to format the XMin YMin XMax YMax so as not to either crash ArcGIS completely, as occurs when I tried using arcpy.env.extent = ...clip.tif theExtent = arcpy.env.extent or theExtent = clip.tif And if I try building the string of coordinates after using Describe to access the information, i.e.: theExtentRaster = clip.tif theDesc = arcpy.Describe(theExtentRaster) theExtent = theDesc.extent theExtentString = str(theExtent.XMin) + ' ' + str(theExtent.YMin) + ' ' + str(theExtent.XMax) + ' ' + str(theExtent.YMax) I get this error: ExecuteError: ERROR 000622: Failed to execute (Clip). Parameters are not valid. ERROR 000628: Cannot set input into parameter rectangle. I also tried adding single quotes or double quotes to theExtentString. So, again, it isn't accessing the information, (I even tried the code snippet in the Extent page you referenced), it is FORMATTING the four coordinates in a way the arcpy.Clip_management command will accept. Any ideas? Thanks, Darlene

‎09-07-2016

I have a raster that I want to clip to a county boundary (no data outside county). It is a stretched NDVI tif, so the values of the raster are 0-255. I tried using the Con function, but it produced an output raster with values from 6 to 66500-ish. I determined that what would work is the raster Clip tool and checking the 'Use Input Features for Clipping Geometry' box. The results are fine -- no data outside the county, correct values inside the county -- EXCEPT that the extent of the output raster is the extent of the county polygon, and I want it to be a different, larger extent (so as to be the same size as other raster datasets). The Python Snippet comes out like this: # Replace a layer/table view name with a path to a dataset (which can be a layer file) or create the # layer/table view within the script. # The following inputs are layers or table views: "...a.tif", "...b.shp" arcpy.Clip_management(in_raster="...a.tif", rectangle="677439.999999999 3721040 678360.000000007 3722960", out_raster="...c.tif", in_template_dataset="b.shp", nodata_value="256", clipping_geometry="ClippingGeometry", maintain_clipping_extent="NO_MAINTAIN_EXTENT") I can replace all the dataset arguments with variables: theInRaster = ...a.tif theCntyShp = ...b.shp theOutRaster = ...c.tif arcpy.Clip_management(in_raster= theInRaster", rectangle="677439.999999999 3721040 678360.000000007 3722960", out_raster=theOutRaster, in_template_dataset=theCntyShp, nodata_value="256", clipping_geometry="ClippingGeometry", maintain_clipping_extent="NO_MAINTAIN_EXTENT") Now, I want the rectangle argument to be equal to the extent of clip.tif. I tried setting the arcpy.env.extent to clip.tif and leaving the rectangle argument blank (""), but it went to the smaller extent of the polygon. So, I need to actually put 'something' in the rectangle coordinates. I tried setting theExtent to several things: theExtent = arcpy.env.extent and then rectangle = theExtent #crashed ArcGIS completely theExtentRaster = ...clip.tif and then rectangle = theExtentRaster #crashed ArcGIS completely theDesc = arcpy.Describe(theExtentRaster) theExtent = theDesc.extent and then rectangle = theExtent or theDesc = arcpy.Describe(theExtentRaster) theExtent = theDesc.extent and then rectangle = theExtent theExtentString = str(theExtent.XMin) + ' ' + str(theExtent.YMin) + ' ' + str(theExtent.XMax) + ' ' + str(theExtent.YMax) and then rectangle = theExtentString and also trying adding either single quotes or double quotes to theExtentString all result in this error: ExecuteError: ERROR 000622: Failed to execute (Clip). Parameters are not valid. ERROR 000628: Cannot set input into parameter rectangle. So, clearly, there is SOME OTHER WAY to define the rectangle. I'm hoping someone out there can help.... Thanks.

‎10-16-2014

Hi Tom, If you have the elevations at the endpoints you can create a TIN -- the elevations would be wildly inaccurate overall, but EXACTLY what you need between the points. In short: Create a TIN using your endpoint elevations (not knowing exactly how your data is organized you'll have to figure out how to assign the correct elevation to each endpoint). Then, do a TIN to Raster, being sure to match the extent and cell size of your DEM. This raster will be garbage everywhere except along the path of the sewer lines, where it will be perfect. You can Polyline to Raster to get a raster version of the sewer lines, use that to extract just the along-the-sewer-lines values from the raster you created -- it will get rid of all the inaccurate elevation numbers everywhere else (that is, not along the sewer lines). Hope this helps! Cheers, Darlene

‎10-30-2013

I have a 1m DEM derived from LiDAR. I go through the usual process -- Fill, FlowDirection, Watershed. The result is that sometimes I'm getting only part of the catchment (see the attached screen shots. The blue outline is from a survey of the catchment area -- which may not be perfect, but it will be close). It appears that there may be too much detail in the DEM? Small rises and ridges that are stopping the flow when in reality it is not a barrier. Is there a threshold setting I'm missing? Or repeat the Fill (will this result in good data being smoothed out as well as the bad?) I'm sure there is more artistry to be applied -- I just don't know what it is! Any help would be appreciated.

‎02-27-2013

Darlene, Just to clarify what happened a bit for anyone else who visits this thread. You made use of the Snap Pour Point tool. The raster that is derived from this tool will have the extent of the input points if you leave the extent settings default when you run the tool. Usually the point layer's extent is smaller than the DEM extent. When you move forward in the hydro workflow (watershed tool) and you use the smaller extent raster as input, the tool's default behavior is to use the smallest extent of any of the inputs. In other words, just the area of overlap between the inputs. You can avoid this by setting the extent to the DEM when you run the Snap Pour Point tool, or like Curtis suggested, when you run Watershed. If you create an envelope of the points using the Minimum Bounding Geometry tool and overlay it with your original watershed result it should be quite clear why your catchments got 'cut' off. Best, Eric You're exactly right about the cause of the problem, though one point needs clarification. The SnapPourPoint raster has the same extent as the original DEM. My particular problem arose in that I used the point shapefile, not the raster, and you are spot on about the extent being redefined. It doesn't seem intuitive that the raster extent would be redefined to a shapefile extent -- though I guess, technically, the 'smallest extent of any of the inputs' would include shapefiles as well as the rasters. THIS is the real point to be made. So, either use the SnapPourPoint raster or define the Extent and the Snap Raster in the Environments! Thanks for explaining why this problem occurred! Darlene

‎02-27-2013

Something to try: Make sure your environment extent and snap raster are set to the flow direction grid for your run of the watershed tool. Holy cow, you nailed it! I NEVER would have thought to try that, as I (obviously wrongly) assumed that if the only raster was the original DEM then the environment settings would default to the appropriate values. Lesson learned -- THANKS!

‎02-27-2013

You are performing the flow direction on the filled DEM, right? Yes I am, but it was a good question to ask!

‎02-22-2013

I have a 1m DEM derived from LiDAR. I wish to determine the watershed catchment above a specific pour point. The Pour Point is in a shapefile. I am working with the tools in Spatial Analyst Tools > Hydrology. I did a FlowDirection, then I did a Sink, and yes, there were some, so I did a Fill. I then repeated the FlowDirection. I also did FlowAccumulation and FlowLength, as well as a SnapPourPoint to make sure my Pour Points were appropriately located. I selected a search of 3 cells, and the point moved down three cells, so I moved it UP three cells from my original location, and my original location was selected, so I know it is an acceptable pour point. With the Flow Length (using the Upstream option and making high values dark) I can see a beautiful representation of the flow. I want to capture the entire extent of the flow into that point. The FlowAccumulation at that point is over 65000, and the upward FlowLength is nearly 600. However, when I try to define the Watershed using the Pour Point, I get just this small catchment immediately above the Pour Point, about 100 grid cell count, NOT the entire catchment. Using the FlowDirection I moved one cell downstream, and got a smaller adjacent catchment of only 40 cells -- so it didn't even include the original try's extent, let alone ALL the upstream extent! How does one set thresholds to say give me the whole thing, not just the immediate little bit. Thanks. I'm attaching a graphic to show what I mean.

‎05-21-2012

I have a binary raster -- 1, 0, and No Data. What I want is 1 and No Data. How do I get rid of the 0 values? Specifically, how do I recalculate the the 0 values to no data/nil/null or whatever the correct term for it is? Thanks, Darlene

‎02-27-2012

Darlene - interesting...I'm assuming your rasters are in the same projection, correct? If you're interested, you can send me your rasters to rleclair at esri dot com. I can work with the scenario and attempt to resolve it. Please advise. Robert, Yes, both are NAD83 UTM16N. I'll be glad to zip them up and email them to you, because I have to embrace ArcGIS (I'm an old, old dog, who still fumbles a bit -- make that more than a bit -- with the new tricks). Because I actually have to advance through the project, though, I reverted back to the old ways: In ArcView3.3, this produced the correct results: ( [Culvert_1].IsNull.Con([Cksw_03m_v0],[Culvert_1])) Thanks so much. Darlene

‎02-27-2012

Robert, Well, that gave me completely inexplicable results. Original_DEM: 3251 rows x 4618 columns, 3m cellsize. Min elevation, 262.03m. Max elevation 305.78m, Mean elevation 280.69m (values rounded). Corrected_DEM: 3251 rows x 4618 columns, 3m cellsize. Min elevation, 265.31m. Max elevation 299.39m, Mean elevation 283.40m (values rounded). The Corrected_DEM was created this way: Line segments were digitized where culverts needed to be "burned in" to the elevation model. Through a number of moves the line segments became the Corrected_DEM, which is NODATA off the line segments and interpolated elevation values along the line segments (now @ 10 gridcells long, each). Also, I set the environment to be the same extent and cell size as, and had the line segments snap to, the Original_DEM. When I did my attempts at the CON, I got ... exactly the same as my Corrected_DEM. When I did YOUR version, I got this oddball result. The properties indicate the same number of rows and columns, the same cell size, but the Min, Max, and Mean elevation values are all 264.57m (rounded) and all the values are null except for one cluster of gridcells in the far upper left of the DEM measuring about 383m x 383m. This is no where near any of the corrections. I did this twice -- once just putting in your suggestions, one using your suggestions AND setting the environment to match the Original_DEM. Same results both times. This should NOT be so difficult! Any further ideas? Thanks, Darlene

‎02-27-2012

I have two rasters -- one is an ORIGINAL_DEM, the second has some CORRECTED_DEM elevation values and otherwise is NODATA. What I want is to create a new raster, where the values are the CORRECTED elevation values where there are corrected elevation values, and otherwise are the original DEM values. In the Tool, I use the following: Input conditional raster: CORRECTED_DEM Expression: I tried leaving this blank, I tried "VALUE" > 0, and I tried "VALUE" <> NULL Input true raster: CORRECTED_DEM Input false raster: ORIGINAL_DEM In each of these cases, I get the corrected DEM values ONLY -- the rest of the values are NODATA -- that is, I'm not getting the original DEM values at all! Thanks for any help....

‎11-16-2011

You will find the Clean tool in: ArcToolbox->Coverage Tools->Data Management->Topology If you don't see the Coverage Tools toolbox, make sure you start ArcMap/Catalog with an ArcInfo license. If you still can't see it, right click ArcToolbox (at the top level or on a blank area) and select "Add Toolbox..." and browse to Catalog->Toolboxes->System Toolboxes and add the Coverage Tools toolbox. OK, clearly not the case with rev10 -- I **do** have an ArcInfo license, and I followed your instructions, but there doesn't seem to be a Coverage Tools toolbox any more?

Online Status	Offline
Date Last Visited	‎03-17-2023 08:39 AM

My Ideas

Latest Contributions by DarleneWilcox

Re: Convert LAS Points to Single Point Shapefile

Re: how to enter 'rectangle' argument in raster Clip

Re: how to enter 'rectangle' argument in raster Clip

how to enter 'rectangle' argument in raster Clip

Re: Elevation interpolation along a (sewer) line

LiDAR DEM is too detailed, catchments are too small

Re: Watershed tool returns only immediate catchment, not entire upstream catchment ex

Re: Watershed tool returns only immediate catchment, not entire upstream catchment ex

Re: Watershed tool returns only immediate catchment, not entire upstream catchment ex

Watershed tool returns only immediate catchment, not entire upstream catchment extent

how to set values to no data/null/nil/whatever!

Re: How to use CON function

Re: How to use CON function

How to use CON function

Re: Cannot locate Clean coverage processing tool

Re: Watershed tool returns only immediate catchmen...

Re: Convert LAS Points to Single Point Shapefile

Re: Watershed tool returns only immediate catchmen...