Light Detection and Ranging, or LiDAR

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[Steven Sobieszczyk] Hello and welcome! You are listening to episode 13 of the Oregon Science Podcast for Thursday, December 2, 2010. I'm Steven Sobieszczyk.

This month's episode focuses on one of the most useful geographic tools scientists have for studying our natural world: Light Detection and Ranging, or LiDAR. LiDAR is a powerful data collection technique that can be used to map surface features, even those hidden beneath the dense canopy of Pacific Northwest forests. USGS scientists use this high-resolution data to create virtual 3-D landscapes, similar to the wireframe worlds found in movies and video games. With these virtual surfaces, investigators can now manipulate, measure, model, calculate, and examine the landscape and discover things previously unseen. Listen in as we uncover how new technologies reveal new possibilities, only in this month's episode of the USGS Oregon Science Podcast.

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[Steven Sobieszczyk] Thanks for joining us. For today's episode we're talking about LiDAR. Here’s a little background. LiDAR is an acronym for Light Detection and Ranging. Similar to SONAR, which stands for Sound Navigation and Ranging, and RADAR, which stands for Radio Detection and Ranging, LiDAR is used to measure and detect objects. However, unlike SONAR or RADAR, which use sound waves or electromagnetic waves, LiDAR uses light, or more specifically, lasers. Therefore, the precision of the data collected are extremely high. In addition, since a typical LiDAR data collection bombards the landscape with millions, if not billions, of laser pulses, the accuracy is also extremely high…in some cases modeling surfaces are as accurate to +/- 6 inches. These laser-related data points can then be plugged into 3-D enabled software to produce a digital version of whatever landscape was originally surveyed. Within this virtual, digital landscape, scientists can then explore, examine, and measure every detail of the study area. They can rotate, zoom, or pan across the surface. They can view features on top of the surface, such as tree canopy cover, underbrush type, or if there are buildings present…the building height, area, and volume. Even more incredible is since there is such a high density of laser bombardment, many of the lasers pierce the tree canopy and reach the forest floor. Therefore, features hidden beneath the tree cover are also surveyed. So not only can surface features be examined, but also features underneath can be shown. By exposing this "bare earth," hidden features become obvious. Things such as landslides, faults, rock outcrops, and stream channels all are visible even in densely forested areas. This is exciting because it allows a very detailed examination of the raw, smooth surfaces of a study area without having to physically remove any of the actual features in real life.

This type of visualization proves beneficial to a variety of different scientific fields. For example, take engineering geologists. They love it because landslide failures just pop out, even under dense tree cover. Geomorphologists love it because it shows stream channel movement, or migration, along riverbanks without have to spend weeks or months traipsing through the mud trying to map it by hand. Geologists routinely use it to pick out faults or see changes in geology, something that used to be much harder and take much longer using traditional aerial photographs. Even biologists and ecologists love it because they can use it to study vegetation characteristics and then relate those aspects to habitat and species diversity. If you are studying the geography of somewhere then chances are acquiring LiDAR for that study area will be worthwhile for you.

Now…the USGS has used LiDAR on studies across the country, including the wetlands in Louisiana, the Grand Canyon in Arizona, and reefs of Hawaii. Locally, recent work in Washington and Oregon has used LiDAR-based elevation models. For instance, volcanologists in Washington flew numerous airborne LiDAR data collection flights over Mount St. Helens back in the mid-2000s to measure and examine dome building during the most recent eruption. Using the elevation data from the different flights, scientists were able to estimate the extruded volumes and growth rates of the new lava dome. In addition, the high-resolution data were used to quantify dome height variations, size of magma conduit opening, and even the mechanics of the dome emplacement. Starting in October 2004 and going through February 2006, around 105 million cubic yards of lava erupted within the Mount St. Helen's crater floor.

In Oregon, most of the LiDAR data are obtained by the Oregon LiDAR Consortium. The consortium is composed of local organizations and city, state, and federal agencies, including the USGS that are all working toward the goal of statewide LiDAR coverage. Every year more and more of Oregon is covered by this high-resolution data, much of which have become available free to the public. Currently, most of the coverage is for select areas along the Oregon Coast and within the Willamette Valley. However, every year this coverage increases, with some areas of greater interest getting multiple flights for multiple years to see actual changes to the landscape. If you live in Portland and are curious about what the world looks like as shown with LiDAR, there is a actually a viewer available online hosted by the Oregon Department of Geology and Mineral Industries. That site is linked in our show transcripts.

To wrap things up, LiDAR is a relatively new technology used for surveying large and small areas. Data can be collected using either aircraft or ground-based instrumentation. Regardless of how it is acquired, the accuracy of the data and the ability to easily manipulate it, make it an extremely powerful tool for scientists.

Well, that’s all we have for today's show. Thanks so much for listening. You can check out all of the links we talked about in today's podcast in our show transcripts. You can find them at our website: or.usgs.gov/podcasts. If our monthly podcast doesn't feed your need for USGS-related news here in Oregon, you can follow us daily on Twitter at “USGS_OR.” As always, if you have any questions, comments, or complaints about the USGS Oregon Science Podcast, please feel free to email us at oregonpodcast@usgs.gov. Thank you for listening. To hear more about other research the USGS is doing around the country or around the world, check out any one of our other USGS social media outlets at usgs.gov/socialmedia. There you can listen to other USGS podcasts, as well as find links to USGS on Twitter, YouTube, Facebook, and Flickr.

Until next time. I’m Steven Sobieszczyk.

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This podcast is a product of the U.S. Geological Survey, Department of the Interior.

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