84Post-processing: Differential corrections applied to GPS posi-tions in a PC - after both rover and reference data are loggedand downloaded. Post-processing is slower but more accuratethan real-time differential correction.RTCM: Radio Technical Commission for Maritime Services.Commonly refers to a format of real-time DGPS format.Reference Station: A stationary GPS receiver logging, orbroadcasting, data from a known point. The data is used fordifferential correction. Reference Station is synonomous withBase Station.RINEX: Receiver Independent Exchange Format. A “univer-sal” GPS measurement data format designed to allow compat-ibility b tween different brands of GPS receivers.Shapefile: A set of GIS files invented by ESRI but publishedas an open file standard readable by most GISs. A shapefileconsists of a map file (SHP), a file containg feature descrip-tions (DBF), a file relating the map locations with the featuredescription (SHX) and sometimes a file containing coordinatesystem information (PRJ).Waypoint: A pre-determined coordinate point to which a GPSreceiver can navigate. GPS receivers can also log waypoints inthe field for later navigation. GPS for GIS receiver have largelyreplaced waypoints with point features.WGS-84 coordinate system: World Geodetic System, 1984.The coordinate system is used by GPS receivers for computingtheir positions.
