Introduction

Elevation data are essential for flood mitigation, conservation management, infrastructure development, national security, and many other applications. The National Enhanced Elevation Assessment (NEEA) was conducted to (1) document national level requirements for enhanced elevation data, (2) estimate the benefits and costs of meeting those requirements, and (3) evaluate multiple national enhanced elevation program scenarios.

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NEEA documented business uses for elevation needs across 34 Federal agencies, agencies from all 50 States, selected local government and Tribal offices, and private and not-for profit organizations. Each need was characterized by the following:

• Data accuracy
• A refresh cycle for the data
• Coverage for geographic areas of interest

Each business activity was described and the expected benefits derived from enhanced elevation data were identified wherever possible. When benefits were expressed as a range of values, the lower number represented the conservative benefit and the higher number represented the potential benefit.

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Benefit-cost analyses were developed and examined for more than 25 program scenarios. Each scenario included a different data- quality level and data refresh cycle- combination. Ten leading scenarios emerged from this analysis.

The estimated costs for each scenario include those for data collection and life-cycle management. The scenario outlined in red is a middle-range option that offers uniform medium- to high-quality light detection and ranging (lidar) data for 49 States and U.S. territories and interferometric synthetic aperture radar (ifsar) data for Alaska. These data would be acquired over an 8-year period and address 58 percent of the benefits associated with the requirements identified in the NEEA.

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An inventory of known high-resolution digital elevation data sources was conducted as part of the NEEA in the summer of 2011. The inventory was completed by the U.S. Geological Survey's Geospatial Liaisons in cooperation with the National Oceanic and Atmospheric Administration and the Federal Emergency Management Agency. The inventory included publically available enhanced elevation data for any area where the coverage was complete for a county or was at least 300 square miles in size.

The following is an overview of the results of the inventory:

• Lidar data have been collected over 28 percent of the conterminous United States and Hawaii.
• Enhanced elevation data (primarily ifsar data) have been collected over approximately 15 percent of Alaska.
• Elevation data was collected at an average annual rate of 4 to 5 percent from 2009-2011.
• The level of overlapping coverage is less than 10 percent.
• The quality of the data varies from project to project.

The following maps resulted from the inventory:

• Publically available lidar point cloud data  (1.8Mb PDF)
• Publically available enhanced elevation data  (2.1Mb; PDF)

The elevation data inventory shapefile that was created as part of the NEEA is shared "as is" and may be downloaded here:

            ElevationInventory2011.zip (ZIP archive; 72.4MB)

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The NEEA was conducted under a contract between the U.S. Geological Survey and Dewberry (a consulting firm based in Fairfax, Va.). Additional support for the assessment came from other Federal agencies: the Federal Emergency Management Agency, the National Geospatial-Intelligence Agency, the National Oceanic and Atmospheric Administration, and the Natural Resources Conservation Service.