A quick look at NGA LiDAR from Haiti    

Posted on Wed, January 27, 2010 by Chris Crosby in 2010 Haiti EQDataNews

As I pointed out in my last post, there has been a concerted effort by a number of groups to acquire LiDAR data over Haiti in the wake of the January 12th earthquake.  In addition to the Rochester Institute of Technology and Navy groups operating in Haiti, the National Geospatial-Intelligence Agency (NGA) is also collecting data using the ALIRT instrument (described here I think).  Some NGA LiDAR data products are available via the NGA Haiti Earthquake Crisis Relief site.  The LiDAR data products are available in a somewhat haphazard form via the Haiti Filtered LiDAR subpage.  Most of the “data” on this page are actually PDFs and PowerPoint files showing images of the data.  However, there are a few actual data files - one LAS point cloud file and a few DEMs in 32-bit GeoTIFF format.

Since this is the first post-earthquake data I’ve seen available to the public, I pulled a few of these files and have been looking at them.  Below is a screen capture of the LAS file (320,900 pts), which is described as the National Palace, but appears to actually be data from a neighborhood just NW of the Palace:

image
(UPDATE 02/04/10 - NGA has apparently removed the actual LAS file)

I gridded the point cloud data above at 25 centimeter resolution and exported it along with the data set footprint to Google Earth.  Shown here:

image
Download the Google Earth image overlay shown above.

These data are pretty impressive, especially when viewed in tandem with the post-earthquake Google Earth images.  There appears to be misalignment between the lidar and the imagery, but that may have been introduced when I gridded and exported the data to Google Earth (there is no metadata associated with these file, only the coordinate info in the LAS header (UTM z18N)).

The GeoTIFF DEMs produced by NGA and available on the site are also interesting to look at.  Here is a 40 cm DEM overlain in Google Earth:

image
Download the KMZ file shown above.

Comparison of the LiDAR data above, acquired January 25th, with the Google Earth imagery which was presumably acquired in the days immediately after the earthquake, shows that there is now a set of large tents (field hospital?) in the middle of the athletic fields that isn’t present in the imagery.

It is unclear at this point how much of the data that NGA is collecting over Haiti will be made available to the public.  I hope that they intend release the full data set in an easy to access manner (e.g. all the DEMs, the las files, or both).  OpenTopography has been in contact with NGA and we’ve offered to host whatever portion of this data set they are willing to share with the scientific community and the general public.  Stay tuned.




very interesting! Excellent example of the power and need for high resolution topography. I hope they share with the rest of us.

By: Ramon Arrowsmith on 01/27/2010


For more of the ALIRT data, look at
https://jtf-haiti-alirt-lidar.box.net/shared/8kxylga1ig

We may soon move this to a better server, but there is quite a bit there for now.  One application so far has been inferring how many mouths there are to feed at various Internally Displaced Persons (IDP) camps.

By: Dale Fried on 02/02/2010


Thanks Dale.  I was recently forwarded that same link by another individual.  What is the pathway by which these data are being loaded onto box.net?  Is this the sole distribution location for these data or are they also available via the NGA site (the NGA LiDAR page is down at the moment...)?  Are there plans to distribute actual point cloud data or just the mix of pdfs, ppts, and tifs currently available?

By: ccrosby on 02/02/2010


The distribution plan is evolving.  I can post updates as we go along.  I believe DEMs should be appearing sometime soon, if they are not out already.

By: Dale Fried on 02/02/2010


I’m sure the community would appreciate the updates.  Through our NGA contacts we’ve offered OpenTopography as a place to host these data if a good alternative is not available.  That offer still stands.

By: ccrosby on 02/02/2010


Very interesting.  It looks like the LAS file has been removed--your link is broken, and I cannot find any LAS files on the NGA site.

Any chance you could post the one file that was released?

The ALIRT Geotiffs are very nice, but I would like to compare with the raw point clouds.

By: Peter Guth on 02/04/2010


Hmmm, that link used to be valid - looks like NGA took the las file down.  My understanding is that the point cloud data from this collection may remain classified, but that the DEM data is likely to be distributed.  I may have more to report on that effort soon.

By: ccrosby on 02/04/2010


The NGA site is
https://www.geoint-online.net/community/ALIRT/default.aspx

They’re still working on making the data files world viewable.

By: Dale Fried on 02/05/2010


ALIRT data is available at
https://www.geoint-online.net/community/ALIRT/default.aspx

By: Dale Fried on 02/07/2010


The ALIRT DSMs are avaialable via FTP at ftp.nga-earth.org.  User ID is anonymous, Password is blank.

As updated DSMs are received they are being posted to that location.

As previously mentioned the ALIRT community is at ALIRT data is available at
https://www.geoint-online.net/community/ALIRT/default.aspx

By: Todd Ham on 02/12/2010




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