How To: Extract LAS BLOB Attributes into a readable format in ArcGIS 10.0/10.1

October 26, 2012

LAS files can store several attribute values per single Lidar point. These attributes are predefined as part of the LAS specification. Often, a common workflow of working with Lidar data within ArcGIS environment involves LAS to multipoint conversion using the 'LAS To Multipoint (3D Analyst)' tool. The tool allows to preserve one or more LAS attributes during the conversion process. According to the 'LAS To Multipoint' tool help, "…LAS To Multipoint loads attributes into BLOB fields in the output feature class...There are no tools on the user interface to access these values. At present, the values can only be persisted. Custom ArcObjects tools can access the values".

The following is an outline of steps on how to use the "Explode multipoints to points with LAS lidar attributes" ArcScripts sample that allows to convert (extract) the aforementioned BLOB attributes into a readable format. The script download link is provided in the ‘Additional Resources' section below.

Please read the information below carefully before you attempt to use the script.

1. Download the tool and extract the .BAS file from the ZIP archive
2. Since VBA is no longer included in the core ArcGIS Desktop package starting in version 10.0, you will have to install VBA SDK first. It is available from the ArcGIS Desktop 10.0 installation media under “ArcGIS Desktop 10\SDK_VBA\setup.exe". Next, if you haven't done so before, you will need to contact Esri Canada Customer Care department to request an authorization code for the VBA extension (it is free of charge with any active ArcGIS Desktop license. Authorized the VBA extension on your computer using the authorization number provided.NOTE: ArcGIS 10.1 no longer provide support for VBA SDK. Thus, you will need to install the VBACompatibility available under respective directory on the ArcGIS Desktop 10.1 installation media. The authorization process is the same as applies to ArcGIS 10.0.
3. Once you have gotten the VBA Extension installed and authorized, open ArcMap and go to Customize > VBA Macros > Visual Basic Editor:
   
4. Inside the Microsoft Visual Basic Editor window, select File > Import File and browse to the .BAS ('ExplodeLASMultipoint.bas') file containing the script. The script is almost ready to run.
5. Before you do so, ensure that the top (i.e. first) layer in your ArcMap Table of Contents is the Multipoint layer which you retrieved upon running the 'LAS to Multipoint' tool.
6. Once you verified that the multipoint layer is on top, click on the GREEN TRIANGLE button (or hit F5) within the Microsoft Visual Basic Editor window to run the script.
7. You will be prompted to enter the name of the output feature class (it will be created inside the same feature dataset as the input multipoint feature class):
   Since this is a VBA script, you won't see any progress bar showing the completion status as the script runs. Thus, be patient and allow some time for it to finish.
8. Upon completion an advisory message will pop-up, and you will be able to access the output dataset from the original database, inside the same feature dataset as your input multipoint feature class (NOTE: the output will NOT be added to ArcMap automatically). The output feature class will contain attribute field(s) corresponding to the LAS BLOB Attribute values in the readable format.

Additional Resources

1. “Explode multipoints to points with LAS lidar attributes" script download:
   http://arcscripts.esri.com/details.asp?dbid=16285
2. “LAS To Multipoint (3D Analyst)” tool help:
   http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#
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