Beyond Push-Button GPS

by Alfred Leick, (M.ASCE), Assoc. Prof.; Dept. of Surveying Engineering, Univ. of Maine, Orono, ME,

Serial Information: Civil Engineering—ASCE, 1992, Vol. 62, Issue 6, Pg. 75-76

Document Type: Feature article


In 1993, the U.S. Air Force Space Command will complete its deployment of 24 satellites for the Global Positioning System, affording 3-dimensional positions and velocities 24 hours a day all around the world. The satellites transmit at two frequencies, modulated by two codes known as the C/A (coarse acquisition) and the P (Precision) codes, plus a navigation message so that the user can compute the position of the satellites as a function of time. Civilians have been using the GPS system with the C/A code since 1983 for surveying and navigation, while the P code is restricted to the military. During the Gulf War, the military lessened its code restrictions so that civilian receivers could be used in the war zone. With use of GPS becoming so widespread, it is imperative that education about GPS, including theory, transcend traditional disciplines via short courses and seminars at conventions as well as in college classrooms. An outline of the theoretical elements of GPS includes geodetic principles, coordinate systems, geodetic datums, height systems, GPS observables, receiver technology, least squares adjustment, high precision networks, standards and specifications, planning a survey, field procedures, data processing and analysis, adjustment and classification, and data management issues.

Subject Headings: Standards and codes | Global positioning systems | Satellites | Military engineering | Information management | Gulfs | Training | Colleges and universities

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