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Scientific Investigations Report 2014–5191

Lidar Point Density Analysis—Implications for Identifying Water Bodies

By Bruce B. Worstell, Sandra K. Poppenga, Gayla A. Evans, and Sandra A. Prince

Thumbnail of and link to report PDF (4.7 MB)Abstract

Most airborne topographic light detection and ranging (lidar) systems operate within the near-infrared spectrum. Laser pulses from these systems frequently are absorbed by water and therefore do not generate reflected returns on water bodies in the resulting void regions within the lidar point cloud. Thus, an analysis of lidar voids has implications for identifying water bodies. Data analysis techniques to detect reduced lidar return densities were evaluated for test sites in Blackhawk County, Iowa, and Beltrami County, Minnesota, to delineate contiguous areas that have few or no lidar returns. Results from this study indicated a 5-meter radius moving window with fewer than 23 returns (28 percent of the moving window) was sufficient for delineating void regions. Techniques to provide elevation values for void regions to flatten water features and to force channel flow in the downstream direction also are presented.

First posted December 5, 2014

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Suggested citation:

Worstell, B.B., Poppenga, S.K., Evans, G.A., Prince, S.A., 2014, Lidar point density analysis—Implications for identifying water bodies: U.S. Geological Survey Scientific Investigations Report 2014–5191, 19 p., http://dx.doi.org/10.3133/sir20145191.

ISSN 2328-0328 (online)



Contents

Abstract

Introduction

Study Area

Data Used in the Analysis

Lidar Point Density Analysis

Elevation Assignment for Void Regions

Lidar Return Density Variability of Void Regions

Assigning New Elevation Values in Rivers, Lakes, and Ponds

Limitations and Considerations

Summary

Acknowledgments

References Cited


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