Satellite surveying has surpassed traditional ground based surveying in both efficiency and accuracy in the past few years. The most powerful of such surveying techniques uses the NAVSTAR Global Positioning System (GPS) satellites, which were developed by the Department of Defense. Measurements of 3-dimensional baselines between GPS receivers separated by 10 kilometers or more are now being routinely performed with one centimeter accuracy. Such measurements can be completed using portable equipment in a few hours or less. The University NAVSTAR Consortium (UNAVCO) is now utilizing GPS for worldwide crustal deformation and earthquake studies. UNAVCO serves the research community in two different roles. The first is the development and testing of GPS terminals and techniques with the highest possible accuracy and efficiency. The second is offering GPS equipment and assistance to the academic community for research in earth sciences, and also providing training, as well as concentrating its research efforts on the improvement of vertical accuracy, precise surveying in a kinematic rather than a stationary mode, development of reliable and well documented baseline analysis software, interactive computing and graphics, data archiving, and application of GPS technology to the detection of "global greenhouse" effects. This renewal award continues support of these activities.
