LiDAR | Droning PH landscape for development and safety

By Diana G. Mendoza

How many trees are there in the Philippines? There is an algorithm for that, but it does not involve tricky numerical figures because it is done by a camera loaded on an aircraft, buzzing above, that can picture where the trees are while flying above the country.

This is what the state-of-the-art Light Detection and Ranging (LiDAR) technology can do and so much more.

It has been a few years since November 22, 2012 when, at the Clark Air Base in Angeles City, Pampanga, LiDAR embarked on its maiden flight consisting of two light Cessna 206 airplanes carrying devices to scan the Pampanga river basin.

That day was the launch of Project DREAM or Disaster Risk and Exposure Assessment for Mitigation, a collaboration between the University of the Philippines (UP) and the Department of Science and Technology (DOST). DREAM is a component of the DOST-led Nationwide Operational Assessment of Hazards project or Project NOAH, the country’s flagship program on disaster mitigation.

The country’s first extensive three-dimensional (3D) mapping program has continued to map more than 20 river basins and areas in the country that are vulnerable to flooding such as the Marikina-Pasig River system and the Cagayan de Oro river. The DOST has a budget of P1.6 billion for the project.

Dr. Enrico Paringit, program leader of the project, said one flight that circles around 60 to 80 sq. km. around the country would take four hours to gather an immense 200 GB (gigabyte) of data.

“It can do rapid and simultaneous mapping of land and water through 3D imagery, which is by far the most effective technique in mapping flood hazards,” he told an interview. “It is rapid because it can fire laser pulses on the surface it surveys at 150,000 pulses per second.”

He explained that the LiDAR is an instrument that consists of an airplane with a laser, a scanner, a GPS or global positioning system and inertial navigation system that sends laser impulses to and receive signals from the country’ landscape to acquire data called point cloud.

The data with a cloud of points is gathered by the use of light from the laser to measure distances. The speed of the signal’s return to the sensor indicates the level of elevation of a target surface — the surface is elevated if the signal returns at a rapid rate back to the sensor.

He said the 3D maps that the flights generated were used to provide government agencies concerned with environment and ecology, environmental monitoring, forest inventory, fault line mapping, archaeological surveys, infrastructure planning and agricultural assessment with data for hazard warnings, risk management and disaster rehabilitation.

Dr. Paringit said flooding is the top concern of the map generation system of the LiDAR because it is able to measure both elevation and depth that are crucial in determining an area’s risks of flooding.

In addition to this essential factor, it is also a cost-effective way of getting accurate data. Floods are determined according locations and modeling approaches such as riverine, coastal and urban, with majority of the technology’s map generation concentrated around river basins.

“Apart from the Philippines, Singapore also has its LiDAR project. But ours has a very extensive 3D mapping in the region and it may be the best,” he said. He also added that the project consists of an all-Filipino team of scientists and engineers.

Dr. Paringit said LiDAR technology is not a new technology as it has been around for three decades especially in progressive countries that have advanced surveying techniques. The scientific capability to take maps and plot areas, he said, has also been around for a decade.

Today, he said flying or circling an area from above is the new technology of looking, assessing and measuring. “LiDAR rhymes with radar because they have similar surveying features,” he said.

These include sensor capabilities that determine the range, height, and direction of objects and the amount of time each pulse takes to bounce back for the LiDAR to calculate its distance from the subject it is measuring.

In current technology parlance, he said it is called droning because of the instrument in flight, or drone. It generates detailed spatial data and geographic information through topographic maps that give an enhanced measure of the scope and accuracy of the data. The UP National Engineering Center processes the data gathered by the LiDAR instruments.

Technologies like LiDAR are crucial now that the Philippines is heating up with the rest of the world due to unabated climate change. In July 2017, the Asian Development Bank’s climate report said coastal and low-lying areas in the region will be at an increased risk of flooding. Nineteen of the 25 cities most exposed to a one-meter sea-level rise are located in the region, 7 of which are in the Philippines alone.

The ADB report said increases in temperature may lead to drastic changes in the region’s weather system, agriculture and fisheries sectors, land and marine biodiversity, domestic and regional security, trade, urban development, migration, and health that may pose threats and crush any hope of achieving sustainable and inclusive development to some countries in the region.

Dr. Paringit said “85 percent of the Philippines is hazard prone,” and that “Filipinos need to have more information about their environment beyond knowing how vulnerable it is to disasters such as flooding, earthquakes and storms.”

With the LiDAR technology, he said data and information can be explained with better clarity. The development of 3D maps is one helpful factor. Unlike Google Earth and Google Maps that only have 2D maps, he said LiDAR maps’ 3D coordinates are “fine-resolution, high-definition, detailed, with vertical accuracy of plus and minus 20 centimeters” maps that produce more accurate flood models that are used to advise communities in advance about devastating floods.

It has been years since the project’s first flood model of Marikina City was put to test during the Habagat onslaught in August 8, 2012 which displaced thousands of Metro Manila residents especially Marikina, a low-lying area.

“It was the first time we gave a warning to residents before the flood. It felt good that we were able to save lives in Marikina because people heeded our warning and moved to temporary safer grounds,” he said.

From then on, LiDAR instruments that have flood models refined up to house level have continued to do all flood models of the major river basins and watersheds that represent 33% of the Philippines’ total land area, in the succeeding years.

Beyond data gathering on floods, LiDAR has also helped in assessing post-disaster damage wrought by earthquakes, tsunamis, storm surges and others. Its most recent activity was flying over Marawi City in December 2017 to assess the destruction caused by the siege of the Islamic city by extremists in May 2017.

“We sent a team to Marawi City to do damage assessment post siege. We forwarded the data that we gathered, such as the estimates of the extent of damage to the houses and buildings, to the Task Force Bangon Marawi and the Department of Public Works and Highways,” he said. “The same data was used in planning the rehabilitation of Marawi City.”

Dr. Paringit, who is also an associate professor in the Department of Geodetic Engineering in UP Diliman, said the technology can also be used in the government’s billion-peso “Build, Build, Build” development program by monitoring its direction in terms of materials and construction.

“We can monitor if the projects purchased the correct volume of materials and so on; anything that can be seen by the camera,” he said. “The LiDAR does not exist on its own. While it is a tool to gather information with enhanced details, it is also an instrument to give people and institutions the basis of making better decisions.”

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