Lighting Up the Battlespace
NEW TECHNOLOGIES ENABLE THE MILITARY TO MAKE GROWING USE OF LIDAR, ESPECIALLY TO MAP URBAN TERRAINS.
Ongoing improvements in computing power and software are increasing the value of Light Detection and Ranging (LIDAR) technology for battlespace awareness.
U.S. forces in Iraq and Afghanistan seeking information on field elevations, obstructions and lines of sight have had access to geospatial data provided by LIDAR since 2005. The military has been using the same technology for several years to identify and map training grounds and to create flight training simulators for airborne missions.
LIDAR is not exactly new, with the first LIDAR sensors being developed in the early 1990s. But advances in computing are new, allowing for the processing of LIDAR’s large data sets, as are software tools that facilitate the visualization and exploitation of that data by military commanders and planners. Experts predict LIDAR technology will grow in use by the military, especially to map the urban terrains that have become more common sites of operations.
LIDAR uses 1.064 nanometer wavelength laser light pulses to gauge distances by measuring the time delay between transmission of the pulse and detection of the reflected signal. A range finder mounted in an aircraft flying at an altitude of 1,500 meters to 2,000 meters in the United States—or 3,000 meters in Iraq— swings back and forth collecting data on up to 150,000 points per second, providing resolutions of one point per meter on the ground and up to 15 centimeter vertical accuracy. An on-board GPS unit keeps track of the aircraft’s attitude, roll, pitch and yaw to correct how the laser is affected by the position of the aircraft. LIDAR can also be used at ground level to collect even more detailed information about terrain topology.
In Iraq, forces are using BuckEye, a system developed under the auspices of the Army Corps of Engineers Topographic Engineering Center. BuckEye combines airborne LIDAR technology with digital color camera imagery to provide pictures to commanders and planners on the lay of the land. LIDAR elevation data supports improved battlefield visualization, line-of-sight analysis and urban warfare planning. The BuckEye system has collected over 12,000 square kilometers of data, primarily over urban areas, in Iraq.
HIDDEN OBJECTS
LIDAR has the advantage over some other geospatial technologies in that it provides accurate elevation data. Better than that, it can also detect hidden objects.
“One laser pulse outbound could result in multiple returns,” explained Chris Parker of Applied Imagery. The laser pulse might hit tree branches before passing to a vehicle hiding beneath them and then bouncing off the ground. Each of these hits would be reflected back to the LIDAR sensor and recorded. For this reason, LIDAR is valuable in penetrating foliage.
“LIDAR used to be considered an expert tool,” Parker said. “Now it has migrated to a wide variety of end users.” The reason for the spread is the development of software that is used to process, visualize and extract LIDAR data. “Before, LIDAR was used by remote sensing experts for specialized applications in areas such as hydrology, geology and seismology,” said Parker. “Now it is a workhorse technology.” LIDAR data can be combined with other data, such as from mapping technologies, to create a variety of visualizations.
The data returned by the LIDAR sensor provides location data on an x-y-z axis, referred to as a point cloud, which can then be visualized in three dimensions. “A point cloud is a return of a series of data points in space, which effectively gives you a location in 3-D,” explained Arlan Pool, technical director for defense business at Mercury Computer Systems, a software developer that creates visualization tools.
“Typically, once you get that data what you want to do is exploit it to understand what structures you are looking at. Exploiting LIDAR data sets is processing-intensive,” Pool added.
Alternatives to LIDAR in the past included oldfashioned surveying. “That was the baseline approach in the collection of elevation information,” noted Stuart Blundell, vice president of Overwatch Geospatial-VLS. Photographic imaging was also used, in a method that requires an expert analyst to derive elevation values.
The Shuttle Radar Topography Mission (SRTM), a survey taken from a space shuttle craft in the late 1990s, which covered 80 percent of the earth’s surface in 10 days, has also been used for topographic data. “While SRTM is a fabulous resource with very broad coverage, LIDAR resolution will be much higher where available,” said Parker.
LIDAR is best thought of as one method in an analyst’s toolbox, according to Parker. Each mission needs to be evaluated to determine its suitability for LIDAR, added Raquel Charrois, a senior project manager at Fugro EarthData.
“It depends completely on the destination area and the desired output,” she said. “A number of variables need to be considered, including the project area, the kind of aircraft, the acquisition altitude and what kind of surface will be modeled.”
LIDAR is not ideal over water because of that surface’s high reflecting properties. “It takes time for the instrument to recalibrate and regain its logic as it interfaces again with land,” Charrois explained. “It is a complicated consideration. You can’t just say, ‘Use LIDAR every time.’”
An advantage of LIDAR is that it can be used well in conjunction with other spectral imaging methodologies, noted Bill Emison, a product manager at Merrick & Company, an engineering firm and provider of geospatial solutions. “You can collect LIDAR data and simultaneously add other sensors on top of that such as hyperspectral, short wave, infrared, and near infra detectors,” he said.
Those kinds of sensors can, for example, detect mineral deposits and hydrocarbons, and can identify plant species. When used at ground level, it can also be used to detect the placement of explosives, such as the IEDs being used in Iraq.
MILITARY APPLICATIONS
The military is employing LIDAR technology in a number of divergent applications. Fugro EarthData, for example, has provided the military with a LIDAR application that provides integrated training range and land management.
“Land forces always want a good terrain model in order to properly choose training ranges,” noted Charrois. At the same time, LIDAR imagery is being used to detect changes in training terrains so that the armed forces can properly maintain those grounds. “We work with the military in this area at over 150 installations in the United States.”
Naval Air Systems Command has used software tools from Overwatch Geospatial to translate LIDAR data into realistic simulations for fighter pilots, according to Blundell. “This allows fighter pilots to train by flying through and above a 3-D representation of where they will actually be working,” he said. “It can also be used to portray different scenarios the warfighter may encounter on the ground.”
Software developed for LIDAR visualizations can portray different aspects of the terrain. For example, software tools marketed by Merrick & Company depict elevations by color coding the image. Users can access a visualization of intensity data—measuring the reflective properties of ground objects—by accessing a separate black-and-white image.
“Software classification, also called data filtering, is a function that is able to look at a point cloud and determine which shots hit ground and what is above,” said Emison. These ground and above-grounds hits can be automatically coded brown by the software when presenting a visualization.
Data extraction, also known as feature extraction, gives the software the ability to recognize certain specific objects returned by the data. Programming the software to be on the lookout for topographical features such as hills or man-made “cultural” objects such as buildings, vehicles or power transmission lines allows those features to be separately and distinctly portrayed in the LIDAR image.
“Manual techniques”—in this case, human brain power—are also applied to the LIDAR data to create these more complex images, Emison noted. “No automated process is as intelligent as human intelligence.”
Feature extraction moves “beyond visualization to the exploitation of LIDAR data to solve problems through mapping,” according to Blundell.
“The software extracts out threedimensional objects such as buildings and stores them in a database for use with mapping software within a geographic information system,” Emison explained. “The extraction process is one where the software receives a set of points in a LIDAR data cloud and is able to automatically classify them as belonging to a particular feature.”
This software functionality translates raw LIDAR data into useful information. The captured feature is stored in a database that accurately describes its geometry in terms of height and its footprint on the ground.
“This gives more power to geographic information systems to do spatial analysis and mapping,” said Blundell. “Over the last five years, there has been a growing recognition that having a standard set of formats for LIDAR data allows organizations to share geospatial information.”
Overwatch Geospatial’s tools include a high degree of automation and can extract over 500 objects per minute, Blundell said. “This can be used by the military to timely and accurately support mission planning.”
The software also includes a semiautomatic feature that allows users to edit images for clarity and contrast. This is a particularly important tool to solve the problem of urban feature extraction for LIDAR systems deployed at the terrestrial level, Blundell pointed out.
Applied Imagery has created a number of tools that use LIDAR data to perform visual analyses of a piece of terrain. For example, a line-of-site tool allows users to plan a motorcade or convoy route with reference to elevations that have line-of-sight access to that route.
FUTURE SYNERGY
As for the future of LIDAR, Charrois expects industry to develop evermore robust computing capabilities in order to handle the growing level of data captured by LIDAR sensors. “As capabilities mature with time,” she said, “sensors are able to collect more information faster which means larger data sets. These are harder to handle and we are always looking to improve and expedite the processing of that data and to find different things that we can extract.”
Blundell foresees a greater future synergy between LIDAR and optical imagery technology. LIDAR data points can be fused with photographic images to create sharp pictures of terrain that also incorporate elevation information.
Mercury’s Pool believes data extraction and feature identification tools will continue to improve and make the process more automated. “Automatic target recognition capabilities will be developed,” he said. “Software will use templates and multiple matching techniques to identify what the vehicle or other object is.”
Further, as LIDAR becomes more prevalent, processing requirements will increase, challenging companies that work on expanding processing power and making it more efficient. Success in that area, in turn, will lead to a push to locate more of the data processing horsepower on board the aircraft or vehicle carrying the LIDAR sensors, Pool predicted.
“You will want to do more of the processing closer to the sensor,” he said. “Instead of sending a host of raw data down for further processing, it will be possible to process that data on board the aircraft and to deploy the LIDAR exploitation tools on the spot. This will increase the value of the LIDAR data because it will create a greater understanding of changes to specific geolocations, and will also facilitate automatic target classification and recognition.”
Related to that development is the continuing quest in the area of military technology to make everything faster, better, cheaper and lighter. In addition, Parker foresees continued and expanded use of ground mobile LIDAR data to be married up with airborne data. ♦
