OpenTopography Blog

Information and discussion related to high-resolution LiDAR topography for the Earth sciences

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Posts from January 2010

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A quick look at NGA LiDAR from Haiti

Posted on Wed, January 27, 2010 by ccrosby in Data • Haiti EQ • News

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:

(UPDATE 02/04/10 - NGA has apparently removed this file so this link is no longer valid) You can download the actual LAS file from NGA here: ALIRT_LIDAR_HTI_NationalPalace_20100120_0218_L3L.las

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:

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:

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.

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Haiti LiDAR

Posted on Fri, January 22, 2010 by ccrosby in Data • Haiti EQ • News

Recent reports indicate that there is LiDAR data being collected by a number of groups over Haiti in the wake of the 12 January magnitude 7.0 earthquake.  These data will potentially be powerful for earthquake relief workers and the scientific community, and should be an important geospatial resource in the recovery and rebuilding of Haiti.

This news article describes the work being done by the Naval Meteorology and Oceanography Command out of Stennis Space Center in Mississippi to acquire LiDAR around Haiti.  These collections are apparently hydrographic surveys of ports and other areas in Haiti using the CHARTS (Compact Hydrographic Airborne Rapid Total Survey) system.  More information about the CHARTS system and the National Coastal Mapping program is available here.

Today, a press release entitled, Rochester Institute of Technology Captures Haiti Disaster With High-Tech Imaging System; World Bank Funds Five-Day Mission, was issued that describes the data collection being conducted by a team out of RIT who are acquiring LiDAR, high-resolution color imagery, and thermal infrared data using a platform called WASP (Wildfire Airborne Sensor Program) designed to detect wildfires.  The press release provides quite a bit of information about the acquisition, data products, and logistics of the collection.  Specifically on the topic of the LiDAR data, the press release states:

The LIDAR capability detects and measures collapsed buildings and standing structures damaged by the earthquake. At the request of the U.S. Geological Survey, Faulring is using LIDAR to map the fault line to estimate how much the earth moved. This information is critical to refinement of earthquake-risk prediction models.

Application of these data to investigations of co-seismic ground rupture is logical and given the tropical vegetation in Haiti I would expect that the data may prove quite useful for locating and documenting surface rupture associated with the earthquake.  This is also a potentially interesting test case for application of LiDAR to post-earthquake scientific investigations, but is not the first time that airborne LiDAR has been collected immediately following an earthquake.  That honor goes to the LiDAR data collected following the 16 October 1999 Hector Mine, CA Earthquake and available for download here.

My understanding is that the RIT WASP data will made publicly available as soon as it has been processed.  At this time I don’t have specific information on how they intend to distribute the data products, but we’ve offered OpenTopography as a potential access point for the data if there is a need to host it someplace.  When we know more about how to access these data we’ll provide an update.

Finally, I understand that the scientific community has deployed at least one terrestrial laser scanner (TLS) instrument to Haiti for post-earthquake investigations.

UPDATE (January 24): Wired Science has a nice article with more information and preliminary images of the RIT LiDAR data discussed above:  New 3-D Aerial Images of Haiti Will Aid Recovery and Research

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Geomorphology: Understanding earth surface processes from remotely sensed digital terrain models

Posted on Tue, January 19, 2010 by ccrosby in Publications • Resources

I’m a bit late on this, but the December 1, 2009, Geomorphology special volume: Understanding earth surface processes from remotely sensed digital terrain models, edited by Paolo Tarolli, J Ramon Arrowsmith and Enrique Vivoni is an excellent collection of papers related to the study of geomorphic processes with terrestrial laser scanning, airborne lidar, and satellite-based topographic remote sensing. 

Ramon kindly provides a link to the volume’s preface for those who are interested.

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AAPG Rocky Mountain Section Meeting Lidar Session

Posted on Mon, January 11, 2010 by ccrosby in Meetings

An interesting Lidar-oriented session at the AAPG Rocky Mountain Section Meeting in Durango Colorado June 13-16, 2010.  Announcement via the GEOMOD-LIDAR-L and ASU LIDAR listservs:

Greetings all,

The AAPG Rocky Mountain Section Meeting will be held in Durango Colorado June 13-16, 2010. In addition to a broad range of technical sessions, the meeting features a session “Multi-scale Observations and the Application of Remoting Sensing and Lidar to Rocky Mountain Petroleum Exploration”.  This technical session is being co-chaired by Tim F. Wawrzyniec (tfw@unm.edu) and Gary Weissmann (weissman@unm.edu).

We invite contributions from all geologic and geophysics disciplines centered around the principle theme of field-based studies that are combined with digital geospatial characterization as applied to geologic problems.  Although lidar technology is of specific interest, we encourage the submission of talks that include studies where seismic, ground-pentrating radar, or other remote sensing approaches that have been deployed to build imagery to enhance our understanding of geologic process.

If you are interested in contributing, please contact either of the technical chairs if you have any questions.  Otherwise, follow either of the following links:

http://www.fourcornersgeologicalsociety.org/meeting_2010/index.asp

or

http://www.aapg.org/meetings/rms/

The deadline for submission is February 1, 2010.

On behalf of the technical committee thanks for your attention and hopefully we will see you in Durango!

Cheers
Tim & Gary

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LAS Conversion Tools:  LAStools and LASUtility

Posted on Wed, January 06, 2010 by ccrosby in Software

The ASPRS LAS format has become the standard for delivery of lidar point cloud data.  However, because LAS is a binary format, a reader of some kind is necessary to ingest the data, visualize it, or perform additional analysis.  Many of the major GIS software packages now support LAS (e.g. ArcGIS) and all of the commercial lidar specific software read and write LAS data.  Some users however lack access to software that will read the LAS format and thus would like to view lidar point cloud data in ascii format.  In these situations I typically recommend the excellent and free LAStools (or LAStools’ Open Source Geospatial foundation relative libLAS), a package of utilities for reading and writing LAS files.  The downside to LAStools is that the utilities are command line-based, which tends to scare away some users.  If you are interested in LAStools, take a look at the short LAStools tutorial that we’ve used in past OpenTopography short courses.

Today I learned about an alternative to LAStools, called LASUtility from an Indian company called GeoKno.  Like LAStools, LASUtility offers the ability to view LAS headers, convert LAS data to ascii and vice versa, merge or subset LAS files, etc.  However, LASUtility is a Java application that includes a graphical user interface (gui) to the commands unlike LAStools.  The fact that it is a Java app also means that in theory LASUtility will run on platforms other than windows (the readme says Windows, Linnux, Solaris), but the download only includes a Windows executable.  LASUtility is a free download, and a free 5 day license is available (read the “Readme.txt” file in the downloaded directory for info on obtaining a license).  It is unclear to me if longer term licenses are free or require payment.

A quick test drive of LASUtility using a sample LAS file (~220 MB .las) indicated that it generally works as promised but is quite a bit slower than the command line LAStools.  There also seems to to be less control over how file conversions are done - for example, the “LAS to XYZ” and “LAS to text” commands don’t allow you to define the delimiter in the ascii file (files are written as tab delimited).  On the plus side, LASUtility provides a simple (but slow) 3D viewer for the LAS file and claims to offer graphical sub-setting of files (allowing users to draw a bounding box), but I couldn’t get the interface to launch.

LASUtility:

If you are working with lidar point cloud data in LAS format, LAStools is a set of utilities that should definitely be part of your tool kit.  If you are command line averse, LASUtility may also be worth a look.

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