Obstructions surveys--the identification and mapping of objects on the ground that might interfere with aircraft operations--are required at all airports. These surveys are used by the airport to analyze when action is needed to avoid or remediate impingements on airspace (e.g., reduce the height of trees near runways); by airlines to analyze flight paths for their aircraft; and by the FAA to analyze and design new instrument approaches, including global positioning system (GPS) approaches. Airports also use these surveys to update airport layout plan (ALP) drawings that may become the basis for restricting the heights of structures that could impinge on airspace and to note locations of temporary potential obstructions (e.g., construction cranes). The National Oceanic and Atmospheric Administration's (NOAA) National Geodetic Survey (NGS), operating under a series of interagency agreements with the FAA, is responsible for certifying that information developed from obstructions surveys meet the requirements for operation of the National Airspace System. Obstructions data collected and information derived from those data for ALP development may go beyond NGS-administered requirements.

Most obstructions-survey data are obtained using field-survey and photogrammetric methods. A traditional NOAA-certified obstruction survey takes approximately 6 months, and a backlog of demand for such surveys far exceeds the funding available under federal programs, so that some airports must operate with obsolete and possibly inaccurate obstructions information. In addition, introduction of new GPS approaches at airports has increased demand for obstructions-survey data and lack of resources for obstructions surveys impedes FAA's ability to support this new technology.

Seeking to reduce costs and enhance accuracy of obstructions surveys, the FAA and NOAA have been conducting research on the use of airborne LIDAR technology. This research has shown promise that airborne LIDAR data can be used effectively in analysis and accurate mapping of obstructions, including treetops and poles.  Development of a cost-effective methodology that airports and their consultants can adopt to procure, process, and use LIDAR data will facilitate adoption of this new technilogy. 

The objectives of this research were (a) to describe requirements that must be met to use LIDAR data in aeronautical obstructions surveys and airport layout plan (ALP) elevation surveys; (b) to recommend procurement specifications and procedures that could be used by airports or other agencies for procuring and using LIDAR data; and (c) to describe the technical bases that could justify acceptance of LIDAR-based obstructions surveys by the NGS, FAA, airports, and airlines.