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Lidar data is become increasingly available and there are likewise new tools to analyze and display the data. LAS is the public file format for the interchange of three dimensional point cloud data between data users. LAS information can be downloaded and has a file extension of *.las. The LAS Dataset was created in order to grant the ability to utilize LAS data quickly in ArcMap. However, with the advent of the new format, new questions are raised, including what types of analysis, geoprocessing tools and toolbar buttons can be used on a LAS dataset. The ArcGIS 10.1 help documentation lists all of the tools that can be used on a LAS dataset within ArcToolbox and on the 3D Analyst toolbar, all with only a few small steps to enable them. What small steps am I referring to?

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Full Extent of the LAS Dataset with the Tools greyed out.



The ArcGIS 10.1 help on interactive toolbar tools for LAS datasets identifies one such step:

However, the tools are not always active when working with LAS datasets and the 3D Analyst toolbar tools. The 3D Analyst toolbar tools are only available when a LAS dataset is displayed as a full resolution triangulated surface. A full resolution surface is indicated in the table of contents when 100% of points are being used to construct the triangulated surface. When the LAS dataset is displayed as a point set the tools will be disabled.


What does 'full resolution' mean? According to the ArcGIS help on the topic, the definition is, "the scale threshold used to control when the LAS dataset will render itself without thinning, using 100% of the LAS points." So once you have modified the settings or zoomed in far enough to see 100% of the LAS points, you can use all the tools in the 3D Analyst toolbar, right? Almost.
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The final step is to choose the Elevation option from the Display As TIN options on the LAS dataset. Once you make that selection, you should see the LAS dataset appear in the drop-down for the 3D Analyst toolbar and the tools should become active.
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Now you can create the profile graph or generate a 3d feature just as you would with a normally recognized surface in ArcMap.


With the release of ArcGIS 10, new tools were made available, allowing you to use 3D objects in geoprocessing tools, and opening up new possibilities for proximity analysis.  One of the new tools is the Near 3D tool, which calculates the three-dimensional distance from each input feature to the nearest feature residing in or more nearby feature classes. However, when using the new 3D analysis tools, it's always important to consider the geometry of the features being used.

Suppose you have a 3D polygon and would like to determine whether 3D points are above versus below the surface of the polygon. Near 3D is a logical geoprocessing tool to determine which points are above and which are below, right?
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3D Points with 3D Polygon

In this particular case, the answer is no.  The results from the Delta Z created in the Near 3D analysis cannot be used because the geometry of the polygon is only maintained at the edge of the polygon.  Therefore, the results will be based on the distance from the point to the edge of the polygon, not the distance from the point to the polygon surface directly above or below the point.

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Points considered negative when only considering the Delta near Z



To  determine whether the point is above and below the polygon surface, follow this workflow instead.
1. Convert the 3d Polygon to a TIN via the Create TIN tool.
2. Use the Add Surface Information tool to add the TIN values to the point.
3. Use the Add XY Coordinate tool if you do not have z-values for your 3D point data.
4. Add a field to calculate the difference.
5. Subtract the field with the TIN Elevation from the z-value of the point.
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Correct output with the field showing the difference field



With this workflow, if the result is positive, the point is above the surface.

So, when using the new 3D Analysis toolsets, be sure to consider the geometry of the features being used.

References

Editing polygons in 3DJeff S. -- Raster Support Analyst
Bitdepth1-300x220.pngThere are many different kinds of rasters that can be used in ArcMap. To better describe and explain these different kinds  of rasters, Esri has created help documentation on technical specifications and supported raster formats.  Included in the documentation is the ESRI GRID format. This is a very flexible format that many users are comfortable using to process and display data. There is a unique aspect to this format that many users are unaware of that is mentioned in the help documentation.

A section in the help documentation on bit depth capacity reads,
A grid dataset is always stored as 32 bit (either signed, unsigned, or floating point), but ArcGIS shows it above as being the most appropriate bit depth with regard to the cell values it contains.

So while the bit depth of the ESRI GRID may say 8 bit unsigned or 16 bit signed, the storage is still 32 bit.  However, the properties in the source tab of the particular ESRI GRID raster may say something different.  This is important when considering the behavior of the GRID compared to other formats like .imgs or .tifs.

This does not affect the average user of ESRI GRIDs, but just something to keep in mind and understand about the format.  So fear not if you create a new ESRI GRID and the bit depth does not match your defined bit depth; it is still okay. Once the data is added,it should report the most appropriate bit depth.  ESRI GRIDs are always 32 bit rasters regardless of what the source properties report.Jeff S. - Raster Support Analyst
Background processing is a new feature that was added at ArcGIS 10. Background processing provides the ability to run a geoprocessing tool and not lose the ability to work within ArcMap.  Instead, the tool progress dialog message has been replaced by a scrolling bar in the lower right corner of the map document.

You can now stack up multiple geoprocessing tools to run in order.  The intermediate progress messages can still be seen when background processing is enabled, by expanding the Results Window.  This can be the best of both worlds, as you can continue to work within ArcMap, but still see information about what step the current geoprocessing tool is on.

 

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Results Tab

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Background Processing Completion

When the background processing completes, a less obtrusive message will appear in the lower right corner of the map document, indicating it has completed.  You can control the time this message is visible under the Geoprocessing Options and adjusting the slider.


I know what you are thinking,  "but where did my captivating progress dialog message go that is usually center stage on the map document?"
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Foreground Processing Message



Well fear not fellow users! You too can return the progress dialog message to its former glory with these steps:

1. In ArcMap, open up Geoprocessing tab.

2. Select the Geoprocessing Options.

3. Uncheck the 'Enable Background Processing' radio button.geoprocessing-options1-240x300.png

Now the next time you run a geoprocessing tool, you will see the familiar message and be captivated again.

There is more information about the background processing here.Jeff S. - Raster Support Analyst
Questions on georeferencing are some of the most common questions that we get in Support. These conversations range from basic how to questions all the way to questions like “Why are the buttons grayed out?”

There are many places you can find georeferencing help. A few of these places are the ArcGIS Desktop Help documentation, the multiple Support Blogs (linked at the bottom), and the technical articles at Esri Support.

Recently, we have been getting a lot of long-time customers using the georeferencing tool calling in because their toolbar is grayed out. If you are having trouble with an inactive toolbar – have no fear! There is a great article that details some of the known issues that can cause problems when georeferencing rasters in ArcMap.

Of the issues described in the article, one of the most common has to do with datum transformations within a map document. When there are layers or rasters in the map document with different datums, the georeferencing toolbar will be grayed out or inactive. To activate the georeferencing toolbar, open a new map document and only add the raster that you desire to georeference.
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Georeferencing Toolbar at ArcGIS 9.3.1

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Georeferencing Toolbar at ArcGIS 10



Always be mindful of which raster you are georeferencing, and always remember to save your solution by rectifying or updating the georeferencing. Otherwise the solution will only be applied to that raster in that map document.Support Blog Posts on GeoreferencingWorking with Rasters: GeoreferencingHaving problems georeferencing your raster image?Jeff S. - Raster Support Analyst
As a raster analyst, there are a lot times I try to "fix" many types of raster data from various online sources. If you're going to get data from elsewhere, there are many reliable sources available for GIS data, some websites that charge a fee, and some that are really well-done free clearing houses and data centers.



A few of my favorite national and state/regional sources for GIS raster data are:

Geo.Data.gov - http://geo.data.gov/geoportal/catalog/main/home.page

USDA Geospatial Data Gateway- http://datagateway.nrcs.usda.gov/

USGS Seamless - http://seamless.usgs.gov/

GeoCommunity - http://data.geocomm.com/

EPA - http://www.epa.gov/geospatial/data.html

Great Lakes Coastal Planning - http://aqua.wisc.edu/cpr/Default.aspx?tabid=85

TNRIS - http://www.tnris.state.tx.us/DataCatalog/Index.aspx

North Carolina One Map - http://www.nconemap.com/

Minnesota - http://deli.dnr.state.mn.us/data_search.html

California - http://atlas.ca.gov/download.html

ArcGIS Online - http://www.arcgis.com/home/

National Hydrography Dataset - http://www.horizon-systems.com/nhdplus/data.php


Thanks for all of the contributions in the comments!

Check out the Resources for Raster Data page on Wiki.GIS.com for additional links and an updated list.Jeff S. - Raster Support Analyst

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