Australian Army Planning Sydney Olympic Security with LIDAR DEM
By Kevin P. Corbley

Thousands of athletes from around the world are gathering this month in Sydney, Australia, to compete in the 2000 Summer Olympic Games, culminating years of training and preparation. Watching the events from the stands will be multitudes of spectators, many of whom began planning their travels to Australia months ago.
      Much of the responsibility for maintaining the safety of both the competitors and fans resides with the Australian Army. Like the people it will protect, the Army has spent countless hours preparing for these games, scrutinizing every inch and angle of the Sydney Olympic Park and considering hundreds of what-if security scenarios.
      Just as today's athletes rely on the most sophisticated conditioning and sports medicine technologies to hone skills and maximize performance in the Olympics, the Australian Army has turned to advanced spatial information technologies to support its preparation for the Games.
      Last year, the Australian Army requested EnerQuest Systems JV of Robina, Queensland, Australia, to acquire highly accurate elevation data of the Olympic Park using the EnerQuest Remote Airborne Mapping System (RAMSª), a unique combination of LIDAR and digital imaging technologies that creates visually detailed three- dimensional views of terrain.
      In Sydney, the result of the RAMS acquisition was a digital elevation model with three-meter ground sample distance which the Australian Army used to generate a 3D perspective of the entire Olympic Park. It details the precise location and configuration of each sports venue, pedestrian corridor, and light post.
      For security reasons, the Australian Army prefers not to reveal exactly how the 3D scene is being used, but experts familiar with similar applications say the Australians are simulating flight paths between venues in case helicopters are needed to handle an emergency. And during such an event, the military can manipulate the scene in an image-processing system to establish sight lines to and from a problem location, anywhere in the park.
      Within minutes, say experts, the Australian military will be able to put a response force into the park, contain a problem site, and quickly work to defuse a situation-all with the help of the 3D perspective.

Combining LIDAR with Imagery
EnerQuest Systems JV is a subsidiary of EnerQuest Systems LLC, headquartered in Denver, Colo. The U.S. company was formed in 1997, specifically to develop a complete airborne mapping system that leveraged the latest in LIDAR and digital imaging capabilities.
      As a result, EnerQuest has deployed three RAMS systems-one in the United States, another in Japan and the third in Australia. A fourth, an enhanced version of RAMS, will be rolled out in the United States later this year.
      "What differentiates RAMS from the other LIDAR systems operating today is the digital stereo imaging sensor," said EnerQuest President Don Wicks. "No other LIDAR that we know of integrates a digital sensor capable of stereo imaging with the laser."
      Each RAMS unit contains a scanning laser altimeter which measures terrain directly by emitting laser pulses from the aircraft to the ground at a frequency of 15 kHz. The laser can collect terrain elevation data over a maximum 7250-foot swath width. Ground sample distance (GSD), which is a function of frequency and aircraft speed, typically averages three-meters for RAMS.
      The new enhanced RAMS will operate at a higher frequency, 30 kHz, enabling EnerQuest to provide one-meter GSD.
      "The push in LIDAR right now is toward a closer GSD," said Wicks.
      The LIDAR collects 250,000 points per square mile. Contour spacing in the generated DEMs ranges from one to five feet, although less than a foot is possible. The absolute elevation accuracy is six inches, and the relative accuracy of points is one inch.
      The EnerQuest digital camera was custom-built for RAMS. It is a large-format panchromatic sensor with a 4096x4096 pixel array. Nominal pixel size is six to twelve inches but can go as low as 3 inches. The camera is capable of collecting stereo-imagery simultaneously with LIDAR acquisition.
      The LIDAR and sensor are both linked to an inertial measurement unit and GPS in the aircraft. This integration performs a dual function. First, it synchronizes the imagery with the elevation collection so they can easily be merged later. Second, these systems calculate the exact location and position of the sensors during operation, eliminating the need for placing and surveying ground control panels.
      "We designed RAMS to remove many of the costly and time- consuming steps often involved in photogrammetric data collection, such as film processing, triangulation, ground surveying," said Wicks. "In large projects, RAMS cuts months off turn-around time and reduces costs between 20 and 50 percent."
      The combination of imagery and elevation measurements offers benefits to both the customer and the operator. The end user, of course, can extract much more spatial information relating to ground features and terrain when the image is draped over the DEM than is possible from the DEM alone. And for EnerQuest, the integrated data set improves overall product quality.
      "Auto-filtering routines can remove about 85 percent of bad points in a LIDAR data set," said Wicks. "In our quality control, we review the stereo imagery to account for the remaining 15 percent. We've found that cars and even cows can throw off measurements."

Protecting the Games
To introduce the RAMS system in Australia, EnerQuest Systems JV held several seminars around the country. At one of these gatherings in Canberra, representatives from the Australian Army were in attendance. They were intrigued with the system for several potential applications, including security for the upcoming Olympic Games in Sydney.
      As a demonstration project, the Australian firm agreed to fly over Olympic Park, which lies just west of downtown Sydney on Homebush Bay. Unlike most RAMS clients, the Australian Army asked EnerQuest to collect only the LIDAR data. The Army already had plenty of its own imagery to drape over the DEMs.
      EnerQuest collected the data while flying its Cessna 402 at an altitude of 6000 feet in early December 1999. The GSD was three meters, and acquisition took less than a day. The DEMs were delivered to the Australian Army as TIFF files. Military personnel there were said to be extremely pleased with the sharpness and accuracy of the data.
      "The DEM is a visually stunning data set because of the interesting shapes of the various athletic venues and the unusual features on their roofs-flagpoles, antennas and solar panels," said Wicks. "You can even see the aisles between the seats in the stadium."
      The U.S. Army Corps of Engineers heard about the LIDAR data set and its uses in Sydney and asked to review the data. The Corps' Terrain Data Representation Branch at the Topographic Engineering Center in Alexandria, Va., was looking for 3D scenes that it might use in security preparation for the 2002 Winter Olympics in Salt Lake City, Utah.
      The Terrain Data Representation Branch provides the U.S. Army and Department of Defense with advanced techniques for visualizing, merging and analyzing terrain and environmental information.
      The Branch was interested in the combination of LIDAR with imagery, and EnerQuest had purchased a commercially available color aerial image of the Sydney Olympic Park from another vendor which it sent along with the LIDAR data to the Corps as an example of the dual collection capability.
      (The Terrain Data Representation Branch used this data to create the two color images of the park shown in this article.)
      "Having imagery acquired at the same time [as the elevation data] is so valuable for security and many other applications," said Tom Jorgensen, chief of the Terrain Data Representation Branch.
      He explained that 3D imagery can play several key roles in planning security for a large event like the Olympics. Recent imagery serves as an up-to-date map showing the precise locations of venues. And military planners can use it to measure distances between those features.
      The elevation data is critical for establishing line-of-sight between various points in the park, he said. This determines where military observers might be placed to maximize their fields of view and take control of an emergency situation. Jorgensen predicted the Australian Army probably also uses the line-of-sight capability in the image to lay out its own radio communications system in the Olympic Park.
      Another favorite military application of 3D imagery is in flight simulators for mission rehearsal. Australian Army helicopter pilots have probably already determined which pathways and roads in the park offer the best clearance for their Black Hawk helicopters to squeeze through, and they have likely practiced flying into those tight spaces in their simulators.
      "In our planning, we also typically examine the layout of terrain to model how the release of an atmospheric dispersal, such as a gas, might roll through an area," said Jorgensen. "It helps us plan our response in advance."
      Although the Australian military is maintaining tight lips concerning its uses of RAMS data in Sydney, it has already notified EnerQuest that it will need to have additional data acquired for other military applications.
      RAMS has been applied extensively throughout Australia in civilian projects, especially those related to the mining industry. Elsewhere around the world, the applications of RAMS run the full spectrum of typical photogrammetric projects such as telecommunications corridor mapping, urban planning, tax assessment, parcel management, and emergency 911 routing.

About the Author:
Kevin Corbley is the principal in Corbley Communications Inc. He may be reached at 303-979-3232, or at [email protected].

Back