Stimulus LiDAR


3D VE navigation
Fig 1 – New VE 3D Building – Walk Though Walls

I’ve been thinking about LiDAR recently. I was wondering when it would become a national resource and then this pops up: GSA IDIQ RFP Hits the Street
Services for 3D Laser Scanning and Building Information Modeling (BIM)
Nationwide Laser Scanning Services
Here is the GSA view of BIM: Building Information Modeling (BIM)

And here is the core of the RFP:

1) Exterior & Interior 3D-Laser Scanning
2) Transform 3D laser scanning point cloud data to BIM models
3) Professional BIM Modeling Services based on 3D laser scanning data
    including, but not limited to:
   a. Architectural
   b. Structural
   c. MEP
   d. Civil
4) 3D Laser Scanning-based analysis & applications including,
     but not limited to:
   a. Visualization
   b. Clash Detection
   c. Constructability analysis
5) Integration of multiple 3D Laser Scanning Data, BIMs & analyses
6) Integration between multiple 3D Laser Scanning Data and BIM softwares
7) 3D Laser Scanning Implementation Support, including:
   a. Development of 3D Laser Scanning assessment and project
       implementation plans
   b. Selection of VDC software
   c. Support to project design and construction firms
   d. Review of BIM models & analysis completed by other
       service providers
8  Development of Best Practice Guidance, Case Studies, Procedures
     and Training Manuals
9) Development of long- & short-term 3D Laser Scanning implementation
      strategies,
10) Development of benchmarking and measurement standards and programs
11) 3D Laser Scanning and Modeling Training, including:
   a. Software specific training
   b. Best Practices

This is aimed at creating a national building inventory rather than a terrain model, but still very interesting. The interior/exterior ‘as built’ aspect has some novelty to it. Again virtual and real worlds appear to be on a collision trajectory and may soon overlap in many interesting ways. How to make use of a vast BIM modeling infrastructure is an interesting question. The evolution of GE and VE moves inexorably toward a browser virtual mirror of the real world. Obviously it is useful to first responders such as fire and swat teams, but there may be some additional ramifications. Once this data is available will it be public? If so how could it be adapted to internet use?

Until recently 3D modeling in browsers was fairly limited. Google and Microsoft have both recently provided useful api/sdk libraries embeddable inside a browser. The terrain model in GE and VE is vast but still relatively coarse and buildings were merely box facades in most cases. However, Johannes Kebek’s blog points to a recent VE update which re-enabled building model interiors, allowing cameras to float through interior space. Following a link from Kebek’s blog to Virtual Earth API Release Information, April 2009 reveals these little nuggets:

  • Digital Elevation Model data – The ability to supply custom DEM data, and have it automatically stitched into existing data.
  • Terrain Scaling – This works now.
  • Building Culling Value – Allows control of how many buildings are displayed, based on distance and size of the buildings.
  • Turn on/off street level navigation – Can turn off some of the special effects that occur when right next to the ground.

Both Google and Microsoft are furnishing modeling tools tied to their versions of virtual online worlds. Virtual Earth 3dvia technology preview appears to be Microsoft’s answer to Google Sketchup.
The race is on and shortly both will be views into a virtual world evolving along the lines of the gaming markets. But, outside of the big two, GE and VE, is there much hope of an Open Virtual World, OVM? Supposing this BIM data is available to the public is there likely to be an Open Street Map equivalent?

Fortunately GE and VE equivalent tools are available and evolving in the same direction. X3D is an interesting open standard scene graph schema awaiting better implementation. WPF is a Microsoft standard with some scene building capability which appears to be on track into Silverlight … eventually. NASA World Wind Java API lets developers build applet views and more complex Java Web Start applications which allow 3D visualizing. Lots of demos here: World Wind Demos
Blender.org may be overkill for BIM, but is an amazing modeling tool and all open source.

LiDAR Terrain

Certainly BIM models will find their way into browsers, but there needs to be a corresponding evolution of terrain modeling. BIM modeling is in the sub foot resolution while terrain is still in the multimeter resolution. I am hopeful that there will also be a national resource of LiDAR terrain data in the sub meter resolution, but this announcement has no indication of that possibility.

I’m grappling with how to make use of the higher resolution in a web mapping app. GE doesn’t work well since you are only draping over their coarse terrain. Silverlight has no 3D yet. WPF could work for small areas like architectural site renderings, but it requires an xbap download similar to Java Web Start. X3D is interesting, but has no real browser presence. My ideal would be something like an X3D GeoElevationGrid LOD pyramid, which will not be available to browsers for some years yet. The new VE sdk release with its ability to add custom DEM looks very helpful. Of course 2D contours from LiDAR are a practical use in a web map environment until 3D makes more progress in the browser.

Isenburg’s work on streaming meshes is a fascinating approach to reasonable time triangulation and contouring of LiDAR points. Here is an interesting kml of Mt St Helen’s contours built from LAS using Isenburg’s streaming methods outlined in this paper: Streaming Computation of Delaunay Triangulations.

Mt St Helen's Contours
Fig 2 – Mt St Helen’s Contours generated from streaming mesh algorithm

A national scale resource coming out of the “Stimulus” package for the US will obviously be absorbed into GE and VE terrain pyramids. But neither offers download access to the backing data, which is what the engineering world currently needs. What would be nice is a national coverage at some submeter resolution with the online tools to build selective areas with choice of projection, contour interval, tin, or raw point data. Besides, Architectural Engineering documents carry a legal burden that probably excludes them from online connectivity.

A bit of calculation (storage only) for a national DEM resource :
1m pixel resolution
AWS S3 $0.150 per GB – first 50 TB / month of storage used = $150 tb/month
US = 9,161,923,000,000 sq m @ 4bytes per pixel => 36.648 terabytes = $5497.2/month

0.5m pixel resolution
$0.140 per GB next 50 TB / month of storage used = $140 tb/month
US = 146.592 terabytes = $20,522/month

Not small figures for an Open Source community resource. Perhaps OVM wouldn’t have to actually host the data at community expense, if the government is kind enough to provide WCS exposure, OVM would only need to be another node in the process chain.

Further into the future, online virtual models of the real world appear helpful for robotic navigation. Having a mirrored model available short circuits the need to build a real time model in each autonomous robot. At some point a simple wireless connection provides all the information required for robot navigation in the real world with consequent simplification. This of course adds an unnerving twist to some of the old philosophical questions regarding perception. Does robotic perception based on a virtual model but disconnected from “the real” have something to say to the human experience?

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