Latest Contributions by EricRice

ArcGIS does this out of the box.  In ArcToolbox, navigate to Analysis > Proximity > Near.   This tool determines the distance from each feature in the input features to the nearest feature in the near features, within the search radius. http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00080000001q000000.htm Regards, Eric ... View more

Hi Gregg, You can try increasing the number of unique records  to render by going to ArcMap Main Menu > Tools > Options > Raster > Raster Attribute Table (subtab) and increase the value from 65,536.  If you using ArcGIS go to ArcMap Main Menu > Customize > ArcMap Options > Raster > Raster Dataset (subtab) and at the bottom you'll find the same parameter.  Set it to something very high like 1 billion. If your still interested in clipping out a smaller portion you can go to ArcToolbox > Data Management Tools > Raster > Raster Processing > Clip. Regards, Eric ... View more

Hi Jim, I think I can get you most of the way there. Let me know what you think of these workflows. Do the Viewshed, and use the visible area as a mask in Extract by Mask to get the DEM that is visible.  Convert the visible DEM to points.  Make those points 3d. Make your observer 3d also (by attribute or by surface value).  Go to 3D Analyst tools > 3d Features > Near 3D. Input 3d observer and 3d visible points. Near 3D (only in ArcGIS 10) http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00q900000005000000.htm If you really need a raster output, calculate the 3d distance of every cell (3d points) to the observer point, then convert the points back into a raster using the 3d distance field.  Then clip it to just the visible portions. If you don't have 10 I could see you doing a combo of Euclidean Distance and creating a difference raster (height difference) between your surface and a constant raster where the observer is.  This would give you sides A and B of a triangle.  Then take the sqr root of A squared + B squared to get C (the 3d distance). ... View more

Check out the Path Distance tool in Spatial Analyst.  Based on my understanding of your desired output, do not input a cost raster, and only input the surface raster (your DEM).  The values in the surface raster are used to calculate the actual surface distance that will be covered when passing between cells. http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//009z0000001q000000.htm Regards, Eric ... View more

The Options from the pulldown were intentionally removed, along with the limited set of functions available on the toolbar. The dropdown list of analytic functions in the Spatial Analyst and 3D Analyst toolbars were a legacy UI that was causing confusion for users. We considered removing them at 9.0 with the introduction of Geoprocessing tools and all this functionality also being available in the ArcToolbox. We decided to provide a transition period to allow people to move away from this functionality, which most have done. Questions about different environments, different appearance of dialogs that appear to do the same thing, bugs related to different behavior, and sometimes different terminology and parameters were causing confusion. We had two options, replace all the functionality on these pulldown menus with the equivalent geoprocessing tools, or remove the functionality and allow users to put what they want on the menus. We chose the latter since we feel most people only used a small subset of tools on the pulldown menu and it is now easy to customize it. If you have specific functionality missing by the removal of toolbar tools and options, please let us know as soon as possible.  Everything, plus more than what was on the toolbar is available in the Spatial Analyst Geoprocessing Toolbox. Note, no matter how much you customize the toolbar in 10 with geoprocessing tools, you won't get the Options dialog back.  Since everything is GP, the Environment Settings will be honored, making the former Options dialog moot.  To ensure pixel alignment, set the Snap Raster parameter in the Environment Settings. Regards, Eric ... View more

Hi Matt, The FocalMean command you're familiar with is not available in the new raster calculator.  The documentation you pointed to is wrong and I will submit a defect to have it changed.  To accomplish this task you need to use FocalStatistics with the mean statistic type within your Con statement. It should look like this: **unspecified**= Con(IsNull("point2ras"),FocalStatistics("point2ras",NbrRectangle(3,3),"MEAN"),"point2ras") Where **unspecified** is my output name and i'm using a 3 x 3 rectangular neighborhood. You may find this link helpful as it discusses differences between 9.x and 10. http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Comparing_Map_Algebra_between_9_x_and_10/00p600000018000000/ What is Map Algebra (in 10) http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/What_is_Map_Algebra/00p600000002000000/ Let me know if this helps. Regards, Eric ... View more

I have a set of arcs that I've converted to 3d.  I now need to recalculate the lengths of these lines, since the 2d length will vary from the 3d length.  I cannot find a way to do this, any help would be greatly appreciated. Technically you didn't need to convert your arcs into 3d.  The Surface Length tool densifies the line at a user defined interval, or by default, the sampling distance is the natural densification of a TIN or the cell size of a raster.  This tool only applies to 9.3.1 and prior.  The input line features should be 2d. In ArcGIS 10 there is an enhanced tool, Add Surface Information, which is the replacement for Surface Length. Surface Length http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00q90000000z000000.htm How Surface Length works (detailed) http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=How Surface Length (3D Analyst) works Add Surface Information http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00q900000016000000.htm Also in ArcGIS 10 is a new 3d length option in the Calculate Geometry tool. e.g. Right click on field > Calculate Geometry. ... View more

Clayton's original suggestion is how you calculate the volume of a multipatch.  Check out the Add Z Information tool. http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00q90000005z000000.htm Under Usage, you can see the properties that are available for each geometry type.  Volume is present for multipatches.  I just tested it and got the volume for my records. If it isn't working for you, check to see if you have closed multipatches by running the Is Closed 3D tool. Regards, ... View more

Hi there gentlemen. I have some information regarding ArcGIS 10 and an explanation for you regarding the problem described in this post.  If you are trying to run Sample on raster datasets in GRID format, the resulting fields will have the names you expect. i.e.  the name of the raster.  However, if you use non-ESRI GRID, then you get the weird names like G_G_G7 or similar.  Prior to ArcGIS 10, all input rasters are converted to GRID for Spatial Analyst functions.  So, for example, one of your inputs was "my_really_long_name_dataset.img"; we will convert that to a GRID, but GRID's have a name length limitation.  While in the background it is named G_G_G7 and that becomes the resulting field name in my example.  Now, in ArcGIS 10, we natively process that IMG (and all other formats) limiting the conversions and scratch files that would normally be created.  A byproduct of this, and in fact an influence on the design was that Sample now returns the field names users are expecting.  There are some caveats, such as output to .dbf which has field name length limitations (not created by ESRI).  If you're migrating to ArcGIS 10, I would also like to inform you about a new tool.  It is called Extract Multi Values to Points.  This new tool is further enhanced by giving the user the option to specifically name the output field.  So if you have "my_really_long_name_dataset.img" and don't want that to be the output field name (in a geodatabase of course), you can name it something more meaningful to you. ArcGIS 10 will be available this week.  I hope this information is helpful! Best Regards, ... View more

Hi Mark, JT7747 is correct in that Viewshed is raster-based only.  However, if you want to perform Line of Sight analysis you can use rasters, TIN's, or terrains for your input surface.  The LOS tool requires the 3D Analyst extension. Viewshed is available with both 3D and Spatial Analyst licenses. Links to review for LOS: http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?id=1223&pid=1221&topicname=Line_of_Sight_(3D_Analyst) http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=How_Line_of_Sight_(3D Analyst)_works Links to review for Viewshed: http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?id=6518&pid=6505&topicname=Viewshed http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=How_Viewshed_works The way Viewshed is implemented enables the user to have full control over the visibility analysis down to the observer level.  If the offset fields, azimuth fields, vertical fields, etc... were exposed in the tool interface then they would apply to all points (or lines).  Our implementation allows the user to have varying parameters for each observer which makes the tool quite robust and capable of doing complex viewshed studies. If you are interested in studying only 1 point, you do have to create a feature class, but you do not have to add all the fields that would be used to control the visibility.  The tool uses the defaults if the fields aren't present. For example, The AZIMUTH1 and AZIMUTH2 items specify horizontal angle limits to the scan.  Values are given in degrees from 0 to 360, with 0 oriented to north. If the AZIMUTH1 and AZIMUTH2 items do not exist in the feature attribute table, AZIMUTH1 defaults to 0 and AZIMUTH2 defaults to 360, implementing a full 360-degree sweep. The default behaviors are discussed in the section, How Viewshed Works, which I have linked to above. ... View more

World Equidistant Cylindrical/Conic should be just fine.  The message here is that you want an equidistant projection.  Since your data is global you should avoid the polor projections. ... View more

Please feel free to check the Cell Tool sample out. http://edndoc.esri.com/arcobjects/9.0/Samples/SpatialAnalyst/CellTool/CELLTOOL.htm The Cell Tool toolbar provide tools to draw cell boundary, cell value, aspect and flow direction arrow as graphics. Best Regards, ... View more

Hi Cedric, Hopefully I understand this correctly.  It sounds like the raster with the smaller extent doesn't even have NoData pixels that would make it have a global extent which is why you are seeing a minimized extent returned on your computations.  To create these NoData pixels, set the analysis extent (SA toolbar > Options > Extent tab) to be one of your global rasters.  In the raster calculator simply evaluate your non global extent raster.  The result should look identical to the original but have lots of NoData pixels now and a global extent.  You can confirm by displaying NoData pixels as a particular color on the symbology tab. From here you can do a few things.  One, continue your computations but embed a Con(IsNull)) type statement in your expression.  Essentially what I'm saying is, where your formerly non global extent raster contains NoData (null), do one calculation, where it is not null, do some other calculation. If you don't like that approach, you can reclassify NoData to be 0 like you suggested in your initial post.  This is assuming values of 0 won't impact your computations.  We wouldn't want you to multiply or divide by 0 probably. 🙂 If you�??re not comfortable with the raster calculator you can use the Copy Raster GP tool and set the output extent in the environments equal to one of your global rasters. ... View more

Its just a shot in the dark without seeing the data, but it sounds like your original data didn't have statistics and when you mosaic the tiles the software generates stats.  Try taking your mosaic in ArcMap and go to Symbology tab.  The stretch type probably says 'Standard Deviations'.  Switch the type to 'None'.  Does your mosaic now look more like you expect? ... View more

Hi Darren, If I'm understanding your question correctly it seems akin to asking how to incorporate tree canopy heights into a surface to have a more realistic Viewshed analysis in a non urban environment. Would you agree? If the goal is to incorporate the building heights (basic obstructions to visibility) I would use the polygon you have with the height field. I'm assuming this is the footprint of said building... Convert your polygon to a raster using the height field in the Value field parameter. When you do this make sure you set the output extent to that of your DEM. This is a critical step. Next you will have to add the DEM and this new raster together. Its not as simple as just adding them together though. You're on the right track with using Map Algebra. Basically you want to say where my building raster is null, replace it with the value of the DEM, and where it is not null, add the two rasters together. It looks like this. [newsurf] = CON(ISNULL([polygrid]),[dem],[dem] + [polygrid]) If you're using ArcGIS 10, the syntax is somewhat different so please reference the Help. Also, if you're using ArcGIS 10 you may want to look at 3D Analyst Line of Sight tools. They now accept multipatch features as obstructions in the analysis. Hope this was helpful. ... View more