Published: Jan 1992
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The NAVSTAR global positioning system (GPS) provides accurate position data which can be used to aid the users of geographic information systems (GIS) in several ways. GPS is a satellite-based navigation, positioning, and timing system. From the data emitted by the GPS satellites, the receivers are able to calculate either two-dimensional (latitude and longitude) or three-dimensional (latitude, longitude, and altitude) positions. GPS, when used autonomously, is accurate to approximately 12 m circular error probable (CEP). In differential GPS, when used with a base station, the accuracy of GPS position fixes improves 2 to 5 m (CEP). For surveying applications, survey-grade receivers are available which are accurate in millimetres. The GIS applications of GPS include: georeferencing photogrammetric or digital map data; ground-checking satellite imagery data; and creating or updating GIS databases with point, line, or polygon digital data. For these applications, commercial GPS receivers are available which are portable, rugged, and easy to use, although a good understanding of the principles of GPS is required to correctly interpret the data involved.
global positioning system (GPS), geographic information systems (GIS), data-base, satellite positioning
Market manager, Trimble Navigation, Ltd., Sunnyvale, CA