Recap: What is navigation?
basics of latitude and longitude beacons Require "Line of Sight" LOS cognitive visual audio electronic
"radio navigation aids" Tools clocks odometer beacons history U.S. Navy Navigation Satellite System "Transit" (1964) 2-D frequency of fixes vary with lat once very 30 minutes to once every 110 minutes Timation - NRL Transit variant - Johns Hopkins APL System 612B - Air Force other DNSS (Defense Navigation Satellite Service) formed in 1969 -> GPS was fully operational in December 1993 current GPS "Navstar GPS" -> GPS goals global coverage continuous/ all weather operation serve high-dynamic systems high accuracy unlimited users! go over privacy concept! beacons 24 satellites 6 orbital planes -> MEO geosynchronous vs geostationary Based on TOA concept System Time (reference clock) Satellite Time (atomic clock on satellite) Receiver Time (local clock) 2-D fix requires 3 satellites 3-D fix requires 4 satellites (clock error and 3 coordinates) Do the example of calculating position in 3-D from foghorn base Go through 3-D analog assume knowledge of satellite position one range -> sphere two range -> circle three range -> two points one is probably on the earth four ranges -> one point Details Signals Two frequencies L1 1575.42 MHz L2 1227.6 MHz future L5 in 2007/2013 (mm accuracy) (CDMA) All satellites broadcast with psuedo random codes that don't correlate short example of psuedo-random overlay two codes C/A code P(Y) "precision" code future M code improvement against jamming information Ephemeris data ranging data Do example of ranging GPS is dual-use military/U.S. allies (PPS) Precise Positioning Service protected by cryptography (AS) Anti-spoofing prevents deceptive jamming (SA) Selective Availability degraded signal through clock error discontinued in May 1, 2000 as a policy decision SA could be removed through decryption position: 22m 95% of the time horizontal 28m 95% of the time vertical time: 200ns 95% velocity 0.2 m/s 95% civilian (SPS) Standard Positioning Service free unrestricted position: 13m 95% of the time horizontal 22m 95% of the time vertical time 40 ns 95% dual frequency can get 4m accuracy History 1960's fragmentation Current GPS Two codes C/A course acquisition P(Y) precision code GPS Alternatives GALILEO European Initiative from 1998 features open service commercial service safety-of-life service authenticated signal public regulated (aka military) search and rescue support 30 satellites GPS compatible scheduled to be operational in 2008 "reality" GLONASS Russian Global navigation satellite system 14 satellites goal 18 in 2007, 24 in 2010 many of the same goals as GALILEO(dual-use, free etc.) BeiDou China currently semi-operational coverage limited to China 3 goestationary satellites over China Requires two-way communication to localize positioned calculated by centralized system based on signal propagation times Plans to develop GPS analog developed in 2005 Japanese Quasi-Zenith System Augmentations Why? Accuracy "Urban Canyons" space-based satellite overlay EGNOS WAAS broadcast on L1 frequency ground-based differential corrections other inertial sensors Applications Land leisure hiking fleet vehicle management Location-Based Service (LBS) Opinonate about this On-start Restaurant Finder Emergency Assistance E-911 FCC mandate AVLS "geofencing" "geocaching" Aviation automatic Dependent surveillance (ADS) collision avoidance optimal routing reduced fuel consumption non-precision approaches VHS radio replacement by certified GPS waypoints independent of ground stations Space guidance attitude determination heading, pitch, roll Internationial Space Station localizes with GPS pictures from NASA's LANDSAT of the Yucatan penisula coupled with a GPS equipped airborne survey enable a national Geographic expedition to find ruins of several heretofore unknown Mayan cities! Maritime navigation maritime construction pylon placement oil drilling