| “We muddled through the hard way and are still one of the few states to have statewide lidar.” | |
| David Carter, Delaware Coastal Programs |
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More and more, emergency and coastal resource managers are using lidar technology to acquire elevation data for incorporation into state and local maps being used for flood and other natural hazards planning. Coastal managers in Delaware were trailblazers in collecting and using lidar data and have learned hard-won lessons they can pass on to other states.
“We muddled through the hard way and are still one of the few states to have statewide lidar,” says David Carter, environmental program manager for the Delaware Coastal Programs in the state Department of Natural Resources and Environmental Control’s Division of Soil and Water Conservation. “Our staff members are now intimately familiar with lidar, its uses, and what you need to do” to collect it.
Carter adds, “Lidar is very expensive to do . . . and in the fiscal climate now, states need to be able to hit the ground running as soon as the data is delivered.”
Measuring Pulses
Lidar is an active sensor—similar to radar—that transmits laser pulses to a target and records the time it takes for each pulse to return to the sensor’s receiver.
The lidar sensor is mounted to the bottom of an aircraft and integrated with Global Positioning System (GPS) and inertial measurement unit (IMU) technology. Measuring the pulse return rate determines the surface elevation and is used to create high-resolution topographic maps.
Delaware’s statewide lidar coverage came from two separate collection projects, undertaken two years apart. At the time these data collection projects were proposed, very few of the state’s employees had experience with lidar data, or had the ability to work with extremely large data sets.
Big Picture Potential
Efforts began in 2002 to get the funding to collect lidar in Delaware in order to develop digital flood insurance rate maps. In addition, coastal managers hoped that the high detail elevation data could be used for habitat studies or vegetation identification.
In 2005, a coalition of the Department of Natural Resources and Environmental Control, U.S. Department of Agriculture, and the Delaware Geological Survey contracted with the U.S. Geological Survey and NASA to collect lidar for Sussex County using NASA’s Experimental Advanced Airborne Research Lidar (EAARL), which is specifically designed to measure submerged topography and adjacent coastal land elevations.
Because Delaware did not have capacity to run the EAARL processing software, lidar-based habitat and vegetation studies were not realized.
“We did not have the capabilities in-house to know the big picture potential, so we deferred to the federal agencies,” Carter says. “We were getting different guidelines and documents, which made it very difficult to sort out what we needed.”
Storm Devastation
On September 15, 2003, the Glenville community in Delaware was flooded by Tropical Storm Henri. After the storm, 172 homes were bought out by using federal, state, and local government resources, and the community was abandoned in 2004.
“Legislators and others were asking how this could possibly happen,” Carter says. “The answer was that we didn’t have elevation data or a monitoring system that would warn us. The reaction was to spend the money to get this data statewide.”
In 2007, the lidar for the remaining two counties in the state was collected by a commercial contractor as part of a statewide orthoimagery collection project.
Processing Problems
Because of processing problems, by the time the 2007 lidar was flown, Delaware managers still did not have usable data from the 2005 flight. As a result, lessons learned were not incorporated into the second contract.
Problems encountered included the incompatibility of the EAARL data and the 2007 lidar, and that a third-party quality assurance and quality control was not conducted, both of which delayed the availability of usable statewide lidar.
Voice of Experience
Having worked through all the problems, Delaware emergency managers and researchers have been able to use lidar to develop statewide inundation maps, are incorporating the data into flood and storm surge modeling, and are using it to create an early flood-warning system.
While they learned the hard way, it should be much easier for coastal managers to collect and use lidar today, Carter says. “There are tools and training available now to work with this data that didn’t exist in 2002.”
In addition, Carter is hoping that the lessons they have learned will be useful to other managers.
“I would recommend,” he says, “spending a whole lot of time on the phone with states who have gone through this.”
For more information, you may contact David Carter at (302) 739-9283, or David.Carter@state.de.us, or Bob Scarborough at (302) 739-3436, ext.14, or Bob.Scarborough@state.de.us.
National Oceanic and Atmospheric Administration Coastal Services Center staff members Dave Easter and Keil Schmid contributed to this article.
Lessons Learned
Here are Delaware’s top five lessons learned about obtaining lidar data. For a more detailed list, go to www.csc.noaa.gov/digitalcoast/inundation/map/obtain.html
Agree on data standards. Before committing to project-specific deliverables, it is important to consider the various end uses. The choices made in data processing or delivered products may limit other uses of the data.
Know the end users’ technical capacity. The hardware and software capabilities of the end users should be assessed to determine appropriate tiling and file sizes.
A common format should be used for an entire state. In Delaware, counties were mapped using different and incompatible systems, causing problems in merging data sets for statewide coverage and in other statewide analyses.
Ensure all data and products are contract deliverables. When developing a contract, ask all the end users to review the contracts to ensure that all the desired data and products are listed as deliverables.
This should include the specification of each data product in the chosen format and, if applicable, resolution.
Metadata and Quality Assurance and Quality Control. Complete and accurate metadata must also be specified with all the deliverables. An important but sometimes overlooked aspect is the quality assurance and quality control of all data sets by a separate contractor or by the end users before final acceptance.
