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LaserMap—A Software Package Designed to Enable the Wide Application of Coastal Topographic Lidar Data

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During the last several years, the USGS Coastal and Marine Geology Program (CMGP) has collected, in cooperation with NASA and NOAA, dense topographic lidar surveys over much of the "lower 48" U.S. coastline and Puerto Rico. Although the immensity of the data set presents challenges, it is actively being used in ongoing studies of coastal change caused by both catastrophic storms and processes that operate over historical time scales. Other applications focused on mapping land cover and wildlife habitat are being developed for National Seashores. Additionally, this rich data set has the potential to aid a variety of other coastal scientific investigations and management applications. Studies of geomorphic change driven by wind, water, waves, or landslides, and investigations of land ecosystems and wildlife habitat may all benefit from highly resolved lidar terrain surveys. Generally, any project that needs fine-scale coastal digital elevation models that can serve as georectified basemaps may find the existing CMGP lidar data holdings to be of benefit.

In practice, the broad usefulness of topographic lidar surveys can be inhibited by difficulties in directly tapping the raw NASA lidar data sets. In their native form, the NASA Airborne Topographic Mapper (ATM) data are not readily compatible with common GIS packages. The NASA lidar data are delivered in binary files in a unique format that evolves periodically due to instrument upgrades. In one typical 4-hr survey flight, the ATM collects about 72 million separate elevation points, easily enough to quickly "choke" a GIS. Also, the geometry of the raw data is inconvenient for direct transfer to most GIS or mapping programs. This is a result of the inclusion of separate data chunks from multiple flight lines, the spiraling data ground geometry caused by the instrument's conical scan, and referencing to an ellipsoid datum. Typically, each separate elevation point requires conversion to commonly used map datums. It is also difficult to isolate the data for a specific study area because those data may be embedded within numerous raw data files that cover coastal reaches exceeding 200 km in length.

screen capture of the LaserMap Level 1 to Level 2 menu
The LaserMap Level 1 to Level 2 menu.

One of our goals in developing LaserMap is to overcome these practical limitations and thereby make the extensive USGS CMGP coastal U.S. lidar data set widely available to a diverse group of coastal scientists. LaserMap spans the processing gap described above to convert dense lidar data sets into fully documented standard data products that are readily ingested by common surface modeling and GIS software packages such as Erdas Imagine, ArcInfo, or ArcView. We have designed the LaserMap package to run through a menu system to enable scientists to prepare their own data sets with minimal instruction. Data products may be created at several levels to allow for flexibility in further analysis using other software. LaserMap supports reference system conversion, the merging of multiple flight line swaths, the sorting of the surveyed elevations by either latitude or longitude, automatic creation of data documentation at each level, and the creation of ready-to-use binary or ascii point files, full precision grids, and scaled digital elevation images. Once a processing job has been initiated through the menu, all operations are transparent to the user.

We are now using a "beta" version of LaserMap to generate suites of data products for U.S. National Seashores and the coast of Puerto Rico. An enhanced version of LaserMap under construction will incorporate faster processing through the porting of several key programs from IDL to C, and will support the creation of quality control data products, and an expanded variety of processing options. Scientists interested in finding out more about the capabilities of LaserMap are encouraged to contact John Brock in the St. Petersburg office (jbrock@usgs.gov; 727-803-8747, ext. 3088).

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in this issue: Fieldwork cover story:
Oil Seep Ecology

Research Oceanographic Instrument Recovery

Lidar Data Software

Outreach Moloka'i Earth Day

Earth Day in St. Pete

Florida Oceans Day 2001

Science Safari

Rocks for Teachers II

Meetings Delmarva Coastal Bays

Oceanology International Americas

Staff & Center News Amy Farris: Physics Honors Day

Falmouth Road Race

Gaye Farris New President of NAGC

Visitor—Dr. Ingo Percher

Office of Communications

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