DISCUSSION AND CONCLUSION
The Global Position System (GPS) and advances in laser and radar remote sensing technologies have allowed the development of ground, air, and sea topographic and bathymetric surveying systems that can rapidly acquire data with vertical accuracy from 1 to 100 cm. Each surveying technique has its advantages with regard to accuracy, detail, aerial coverage, survey environment, availability, and cost. The NASA topographic Synthetic Aperture Radar (TOPSAR) system has the capability of acquiring 10- kilometer swaths of data with moderate horizontal resolution and vertical accuracy. It can also operate above cloud cover making it very versatile for rapidly surveying broad regions. Airborne laser systems can provide more accurate and detailed data than TOPSAR, but they cannot survey as rapidly or in cloudy conditions. Geodetic GPS ground surveys are highly accurate but cover less area and are restricted to particular environments where driving or walking is practical. Continuing development of these systems will undoubtedly change what the relative advantages and disadvantages of each are, but future surveys of coastal zones may take advantage of each system.
GPS ground surveys can serve to calibrate and assess the accuracy of airborne laser surveys and provide highly accurate topography for particular environments, such as the beach. Airborne laser surveys can provide less accurate but wider and more continuous coverage than ground surveys, which is needed for coastal dune and wetland areas. Select laser surveys can serve to calibrate, evaluate, and selectively update regional topographic models acquired with radar. Finally, bathymetric surveys acquired in a GPS reference frame can help create seamless topographic/bathymetric models.
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