Garmin GPS 25 LP Technical Specification

Garmin GPS 25 LP Technical Specification Manual pdf 12 page image

81) Transportation over distances further than 1500 kilometers2) Failure of the on-board memory battery3) Stored date/time off by more than 30 minutesSee Section 4 for more information on initializing the GPS 25LP.2.3 NavigationAfter the acquisition process is complete, the GPS 25LP will begin sending validnavigation information over its output channels. These data include:1) Latitude/longitude/altitude2) Velocity3) Date/time4) Error estimates5) Satellite and receiver statusThe GPS 25LP sensor boards will select the optimal navigation mode (2D or 3D) basedon available satellites and geometry considerations. When navigating in the 2D modethe board set utilizes the last computed altitude or the last altitude supplied by the hostsystem, whichever is newer. The host system must ensure that the altitude used for 2Dnavigation is accurate since the resulting position error may be as large as the altitudeerror. See Section 4 for information altitude initialization.The GPS 25LP will default to automatic differential mode -- “looking” for real-timedifferential corrections in RTCM SC-104 standard format using message types 1,2,3 or9 and attempting to apply them to the satellite data in order to produce a differential(DGPS) solution. The host system, at its option, may also command the board set tochoose differential only mode. When navigating in the differential only mode, the boardset will output a position only when a differential solution is available.2.4 Satellite Data CollectionThe GPS 25LP sensor boards will automatically update satellite orbital data as theyoperate. The intelligence of the board set combined with its hardware capability allowsthese data to be collected and stored without intervention from the host system. A fewkey points should be considered regarding this process:1) If the sensor board is not operated for a period of six (6) months or more, the unitwill “search the sky” in order to collect satellite orbital information. This process isfully automatic and, under normal circumstances, will take 3-4 minutes to achieve