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University of Houston Cullen College of Engineering

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College Adds National Center Focused on Airborne Laser Swath Mapping

By: 

Erin D. McKenzie
Shrestha
Shrestha

The National Center for Airborne Laser Mapping (NCALM) and the groundbreaking researcher leading it, in January, moved operations to the University of Houston.

Ramesh Shrestha, Hugh Roy and Lillie Cranz Cullen Distinguished Professor of Civil and Environmental Engineering, brought NCALM to UH from the University of Florida. He’s been director of the center, focused on ground-based scanning laser technology and airborne laser swath mapping (ALSM) research, since it was established in 2003.

The addition of the national center, funded by the National Science Foundation, fulfills a major aim of the Cullen College’s Strategic Plan, which guides in building a national reputation for the university and eventually redefining the college as a top 50 program.

“In addition to the prestige of this nationally-funded center, NCALM’s relocation to the University of Houston is extremely significant because of our focus on high-impact research,” said Joseph Tedesco, Elizabeth D. Rockwell Chair and dean. “Sustainability is one of our core areas of research. The addition of Ramesh and his team to the Cullen College will enhance our ability to conduct pioneering research in areas such as environmental studies, homeland security, disaster recovery, oil and gas exploration, and wind farm site planning."

Shrestha brought much of his Florida team with him to Houston where they now operate NCALM jointly with the University of California-Berkley.

“With the center we have brought laser mapping’s uses to the forefront,” said Shrestha. “We expect to continue to have that impact at our new home in Houston.”

At UH, the group plans to work to establish curriculum catered to the specialty and eventually add a graduate degree in geosensing systems engineering. This is in addition to carrying out research far surpassing what’s capable in laser mapping to date.

While NCALM has existed for close to seven years, Shrestha’s work with laser mapping goes back much earlier—to the 1990s when the niche research area was just making its debut. It’s when he met Bill Carter, who later helped Shrestha establish NCALM and now works as a research professor at UH. Together they saw its potential to far exceed what was possible with many traditional methods, including airborne photogrammetric mapping, which uses cameras to detail terrain.

“Laser mapping had the ability to work day or night, and generally map areas even though they were covered by forests and other vegetation where photogrammetric methods couldn’t,” said Carter.

It wasn’t long before other scientists would see its same benefits. Even more so as the two developed techniques to remove and minimize some of the errors seen in the early years. Their equipment, also, was fine-tuned to collect even more data.

Their system now maps as many as 167,000 points per second compared to the 3,000 they were able to achieve when they first started.

Since then, their work has been featured in publications including Physics TodayScientific American and Laser Focus World and has even changed the way the state of Florida monitors erosion on its coastline. It’s produced the highest resolution 3D images of the San Andreas Fault in existence and taken them across the country to map Mayan Ruins in Belize, volcanoes in Hawaii and the swollen Cedar River in Iowa that poured over its banks and nearby levees at 500-year flood levels causing the evacuation of thousands in 2008.

Though the impact of their work is already far reaching—their plan for the coming years ensures they are not close to done.

Aided by the National Science Foundation, NCALM researchers are exploring the possibility of using Light Detection and Ranging (LiDAR) to map everything from glacial movements to the migration of penguin colonies in Antarctica.

Using LiDAR, researchers take measurements of the ground’s surface from their Cessna 337 Skymaster airplane.

From roughly 2,000 feet, this remote technology measures properties of scattered light through the use of laser pulses. Thousands of small cone-shaped pulses travel through a hole in the bottom of the plane to the ground below. A unique detector picks up rays reflected from the ground. Then, each point’s distance is determined by measuring the time delay between the transmission of a pulse and the detection of reflected signals.

The plane’s location and movement in the air are tracked by an inertial measurement unit (IMU) fixed inside the laser system along with a GPS receiver mounted to the plane, and others on the ground. Both are used, along with the laser data, to produce detailed 3D topographical images of the terrain.
In coming years, the UH group plans to develop a next generation LiDAR system. The unit, less expensive than commercially available systems, would allow for some of the most accurate, highest resolution observations possible in laser mapping.

“We want to develop a system like no one else has developed,” said Shrestha. “It would really change what could be done with this technology. It would have new features, be faster, smaller and capture more each flight than we can today.”

This system would use a much shorter pulse length laser, Shrestha said. This would increase the number of points they could map per second to 800,000—adding to data accuracy and reducing the amount of time in air needed to collect the information. On top of this, it would be able, for the first time, to penetrate shallow water depths.

Inside the walls of the college’s buildings, the team will also work share their knowledge of the field through a newly designed curriculum. They’ve already begun to interview candidates for new faculty positions that could make their dream of developing a graduate degree option in geosensing systems engineering, a reality within the next year.

A native of Nepal, Shrestha attended Tribhuvan University, earning his bachelor’s degree in math, physics and statistics. He also holds a bachelor’s degree in land surveying sciences from North East London Polytechnic, a master’s in civil engineering from Oregon State University and a Ph.D. in civil and environmental engineering from the University of Wisconsin. He was a tenured professor with the University of Florida—serving them in a variety of capacities since 1986—before signing on at UH.

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