When LIDAR came down to Earth, mapping projects took off
Second of four parts
Sometimes it takes a crisis to spur innovation.
Such was the case with creation of the Red River Basin Decision Information Network (RRBDIN), and its LIDAR mapping of large swaths of North Dakota, Minnesota and central Canada, said Charles Fritz, director of the International Water Institute.
"In the Red River basin we had a major flood back in 1997. That's when Grand Forks went under," Fritz said. "My organization actually was one of the outcomes from that flood." In the wake of the flood, the Federal Emergency Management Agency took action that resulted in the creation of the RRBDIN, which is managed by the International Water Institute with support from the U.S. Army Corps of Engineers, North Dakota State University Extension and other partners.
"When the 1997 flood hit, we had a huge problem because the only things we had to work with were old [U.S. Geological Survey] maps," Fritz said. Even with the obvious need for better information, FEMA and state funding weren't enough to do the job. "At the time, in 2000, we knew LIDAR was available. We were looking at different technologies to acquire better elevation data, but the numbers were astounding. I mean, we were talking about $35 million."
LIDAR, or light detection and ranging, is a mapping technology that bounces light emitted from a laser source, typically aboard an aircraft, and captures the return to build a detailed map of an area. It’s been around for 50 years, but until recently was an expensive and cumbersome technology limited to specialized uses.
By 2005, however, "Costs were coming down, and the technology was improving," Fritz said. "We said OK, let's move on this."
In 2009, the RRBDIN finished its first pass, collecting LIDAR data covering 54,000 square miles. The result was 8 terabytes of data that the team needed to make available in a useful form. Since then, the team has been working to develop and deploy a series of online tools.
"We did not want have a situation where everybody in the basin had to know ArcView if they want to use the LIDAR data, so we put together the online viewer," Fritz said. "There are some really cool tools in there."
RRBDIN's LIDAR viewer allows users to create and customize maps with elevations down to 2-foot contours or spot elevations. There's also a forecast display tool. When the National Weather Service generates a forecast of a flood in Fargo of, say, 38.5 feet, "What does that mean from an inundation and extent standpoint?” Fritz asked. “We can take the LIDAR data, combine it with that 38.5 feet forecast and produced an interactive map that shows the extent of the flooding."
Fritz said the LIDAR data can be combined with all sorts of other data. It can, for example, be used to determine where and to what extent nutrients will flow in irrigated fields.
"We're talking about efficiencies here, where we can get the most bang for the buck, whether it's a flood damage reduction project or water quality project or natural resource enhancement project," he said. "All of that is predicated on the LIDAR data."
When he started the project, Fritz felt like he was a voice in the wilderness. He spent a year and a half trying to convince people that the project was important to them. "Now," he said, "I can tell you that with no exceptions the people who have experience with the data that we have collected are all saying that it is the best thing since sliced bread. Even most local watershed districts will not start a meeting unless they have that LIDAR viewer open on the table."
While Fritz's team is focused on building more applications to use the data, they are also looking forward to a fresh collection of data. "Since we completed data collection in 2009," he said, "there's been a lot of work, especially in the major metropolitan areas. Fargo, Grand Forks. They put up flood dikes, etc., so now we are talking about how we're going to update the current LIDAR data set."
If flatness is a hydrological challenge in the Red River Basin, rugged terrain is a major challenge in Oregon. Feet-on-the-ground surveys of forest inventories, for example, are particularly time-consuming and, therefore, expensive and quickly outdated.
Scanning from the air is much less costly. "It ends up being about offsetting costs," said John English, LIDAR data coordinator for Oregon's Department of Geology. "It is allowing people to save money on these long surveys."
With two specialists – English and one other scientist collecting and organizing the data – the state of Oregon covers between 5,000 and 7,000 square miles per year at a cost of $3 million to $4 million. So far, the team has collected LIDAR data on 26 percent of the state, focusing first on the more heavily populated western half. The state also has approximately 25 GIS analysts working with the data for a variety of agencies and purposes.
The airborne LIDAR fires eight points per square meter, more than 100,000 pulses per second. According to English, that's enough to ensure that even in dense forest, some of the points reach the ground. Comparing the distances of pulses reflected off the tree tops and those reflected off the ground allows the team to calculate the heights of trees very accurately. And not only that, the full array of returned pulses allows the team to survey undergrowth, too.
Oregon's LIDAR efforts, of course, aren't restricted to forest inventories. In fact, the first use of LIDAR was a joint effort of the state's Department of Geology and Mineral Industries and the U.S. Geological Survey to conduct a landslide study in the Portland area in 2004. They also use the data for habitat analysis assessment.
"People are finding more uses for it," English said. "Municipal mapping of streets, measuring volumes for displaced sediment, flood mapping, hazard mapping. You can even detect wear and tear on roads. It can do a rough survey on everything in an entire city. If you have a house and you know its height, and there's a flood, we can infer how many houses are totaled according to FEMA. Right now we’re producing the most accurate flood-inundation maps ever made."
English says the plan is to scan the entire state. "But we're trying to do it in a methodical way. Primary areas of interest are places where work is being done and where humans interact with the environment,” he said. “So we've covered about 98 percent of the population of Oregon."
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