Latest Contributions by EricRice

There are multiple Clip tools in ArcToolbox.  You want the Clip tool located in Data Management Tools > Raster > Raster Processing > Clip.  It will clip to the geometry of the shapefile/feature class just the same as Extract by Mask. You might also want to check out Zonal Histogram. You won't need to clip the data before hand to calculate the distribution of landuse within each designated area. Eric ... View more

Eric, Split Raster is a viable tool but you would have to fill out the parameters so the output rasters aligned with your polygon records. If you prefer not to use this tool, you can make a very simple model using the Clip tool.  In the model, add an iterator for Feature Selection.  The iterator will loop through each polygon record and use its geometry to clip the raster. Attached is a graphic of the model to do this.  Here are examples of using iterators in ModelBuilder . Note, Iterators are only available in ArcGIS 10.0. Regards, Eric ... View more

Steve, If the data is already in the wrong location, re-projecting the data to the correct coordinate system will do nothing to resolve the issue.  It will still be in the wrong place.  You need to define the coordinate system to be what the data was collected in. Most raster data out there doens't need to be imported since we support so many formats.  What did your data start as?  i.e. an ASCII file perhaps?  How did you import your data?  What coordinate system is the data supposed to be in? How is the cellsize defined in whatever format it was in prior to importing? A few more details from you and I'm sure we can sort it out. What version are you using? Regards, Eric ... View more

Hi Cat, I think you should check out the Raster to ASCII tool for this.  An example of the resulting raster is below.  You can open the ascii file in any text editor.     NCOLS 480     NROWS 450     XLLCORNER 378922     YLLCORNER 4072345     CELLSIZE 30     NODATA_VALUE -32768     43 2 45 7 3 56 2 5 23 65 34 6 32 54 57 34     35 45 65 34 2 6 78 4 2 6 89 3 2 7 45 23 5 ... Regards, Eric ... View more

Bojana, There are many options for you. Given your description of the data you can only create points from it for now.  Once you have the points you can directly convert those points to raster, or interpolate a new surface from the points. Please read the documentation for each method below.  You will have to have 3 columns in your file if you want a PointZ feature class. e.g. X, Y, Z.  The first two  methods only require an X and a Y field though. 1. In ArcMap, Click File > Add Data > Add XY Data.  (Adding x,y coordinate data as a layer) 2. Run the Make XY Event Layer geoprocessing tool. 3. Potentially, you can use the ASCII 3D to Feature Class tool available in 3D Analyst. Regards, Eric ... View more

Greetings, I would definitely suggest using ArcGIS 10.0 for this so you can take advantage of Iterators in Model Builder.  You will want to create one point feature class containing all of your points.  Then use the Iterate Feature iterator to loop through each point.  To clip the resulting viewshed to the Radius2 distance, you will want to use Get Field Value and pass that into the Buffer tool as the distance value.  With the polygon created by Buffer, you can extract the resulting viewsheds according to the polygon geometry.  Attached is a screenshot of the model I used to test this. I recommend checking these out since the model makes use of both. A quick tour of using iterators for iteration�??(Looping) A quick tour of using inline variable substitution Regards, Eric ... View more

HI Kevin, I recommend signing up for ArcGIS 10.1 beta program.  Beta will be in a few weeks.  You will want to check out the Stack Profile geoprocessing tool.  It creates an output table and optional graph recording the profile obtained by draping line features over one or more surface types and multipatch datasets.  We'd love to get feedback during beta from you. The current profile tools are only surface aware so they won't include multipatches in the resulting profile. Regards, Eric ... View more

Jim, I can reproduce that.  Please submit through normal technical support channels. Regards, Eric ... View more

Let me try to get to these questions individually from most recent post to earlier ones. Q: I've already set the NoData values to zero. How do I "specify a spatial extent to match the larger raster"? What tool am I supposed to use to do this? A:  The tool is called Copy Raster.  In the tool dialog you need to click on the Environments button.  Set the Output Extent to your largest raster, or your study area boundary, or whatever you used to define the extent of the project.  For this isolated case make sure you set the snap raster to be the largest raster (the same as the one used for output extent).  Once you have increased the number of NoData pixels in the data (by increasing its extent) you will have to set those to zero as well, so please repeat whatever method you used to set NoData to zero. Syntax: Con(IsNull("raster"),0, "raster") Comment:  It's not a requirement to convert NoData to a value of 0.  Thats what we have Con(IsNull() for. Q:   When creating the rasters from features, the resulting raster extent is only as big as the selected features extent, hence the size difference.  Is there a way to manage the raster extent when converting from feature to raster in this way? A: Yes.  When converting the features to raster go into the Environment Settings and set the Output Extent, Snap Raster, and Cell Size parameters .  This will ensure each resulting raster has the same extent, cell size, and that the pixels exactly align with one another (see Snap Raster).  Doing this step during the conversion process will make summing the rasters later a lot easier. Q:  If I'm just doing a simple raster operation like "[RasterBIG] + [RasterSMALL]" where does the Con(IsNull) statement go? A:  Con(IsNull() is used for specific scenarios, like when someone doesn't want to convert NoData to 0 (zero) before doing some arithmetic.  To be specific about where to put the statement let me outline my assumptions: 1. RasterBIG and RasterSMALL have the same extent, cellsize, and have exact pixel alignment. 2. RasterSMALL has fewer 'real' data pixels when compared with RasterBIG. 3. NoData has not been converted to zero. The statement would go like this:  Where RasterSMALL is null, give it the value of RasterBIG; where RasterSMALL is not null, add RasterSMALL to RasterBIG. Con(IsNull("RasterSMALL"),"RasterBIG, ("RasterSMALL" + "RasterBIG")) Good luck and let us know if you have any follow up questions! Regards, Eric ... View more

Eric, When using the Cost Path tool to derive the path of least resistance, its my understanding that it requires two input points, A and B. It then traces the shortest path from point A to point B. However in Arc 9.x the shortest path tool only required one input point, A, and it then traced the shortest path from point A to the edge of the DEM, which effectively becomes point B. Therefore the shortest path tool and cost path tool are slightly different. I have a similar problem to Claire as regards tracing a surface water run-off path into the river/sea and it would be great if you could advise of a similar tool in Arc 10. Kind regards, Tony Hi Tony, The Shortest Path tool and the Cost Path GP tool are the same tool with different names. I don't have 9.x installed to take the screenshots necessary to highlight this so I'll just point you to some documentation. Under Analysis Concepts > Distance Analysis > Least Cost Path and Least Cost Corridor you'll find  generic information regarding what cost path/corridor analysis is and how to perform it in ArcGIS.  On this page you will find instructions (Links) to Learn how to calculate least cost path using the Spatial Analyst toolbar and to Learn how to calculate least cost path using the Cost Path tool In the Usage Tips section (for the GP tool documentation) it states the following: "Cost Path can also be used to derive the path of least resistance down a digital elevation model (DEM). In this case, the DEM will be the input cost distance raster and the flow direction raster will be the input cost backlink raster. Valid flow direction raster values are 1, 2, 4, 8, 16, 32, 64, and 128; valid values in the backlink raster are 1, 2, 3, 4, 5, 6, 7, and 8. Both of these rasters are acceptable." Attached are screenshots of a simple model I made and the results overlaid on a hillshade to give you some perspective. ... View more

Oliver, When summing rasters with different extents, the normal behavior is to output just an area where the two can actually be summed together.  Hence, you see the output has the extent derived from the smaller of the two inputs.  How you manage this situation depends on what your desired output is.  For example, if you want the output to sum where they overlap, but return the original value from the larger dataset (non overlap area), then you have to use a Con(IsNull) statement.  Ideally, your data should have the same cell size, same extent, and be snapped to the same underlying grid via setting a snap raster somewhere prior in your workflow. Something to think about. Pixel value + NoData Pixel = NoData Pixel Pixel value + 0 = Pixel value Pixel value + Nothing (because your extents are different) = Nothing. What would you like the output values to be for the non overlapping areas? Regards, Eric ... View more

Greetings, Please go to ArcToolbox > 3D Analyst Tools > TIN Management Toolset > Create TIN tool.  If you need to update the TIN later, there is the Edit TIN tool in the same toolset. Regards, Eric ... View more

Is there a way to clip a raster with a polygon but keep the outer portion? (ie, to create a donut?) Andrea, You can use the Mask button on the Image Analysis Window in ArcGIS 10.  Image Analysis window: Processing section Regards, Eric ... View more

Greetings, In many cases you have to tell the software what to do if the statement is true.  You can consider using a conditional statement in this case if you want the output raster to have the same values as the input, but just be a subset of the full data range.  The statement below worked well for me. output =Con(("Raster.tif" >= 500) & ("Raster.tif" <= 2000),"Raster.tif") If you want the true statement to be 1 and false to be 0, and not worry about maintaining the real input values you can just use this: output = ("Raster.tif" >= 500) & ("Raster.tif" <= 2000) Regards, Eric ... View more

Agnar, You need Spatial Analyst.  Here is a good starting point. An overview of the Hydrology toolset Regards, Eric ... View more