16-11-2012, 05:46 PM
Global Positioning System
GPS_intro.ppt (Size: 5.16 MB / Downloads: 60)
Basic Concept
Receivers communicate with Satellites
Communication (signal delay) determines distance
Distance from multiple satellites determines location
Requires very precise clocks
Satellites use atomic clocks (0.000000003 seconds)
Receiver’s clock corrected by satellites
More satellites, widely spaced provides better results
Longer duration of data capture provides better results
Applications
Military (DoD) – civilian uses now exceed military
A ‘Free Utility’ maintained by the Air Force
Space Travel (NASA)
Survey, Mapping & GIS
Resource and Asset Management
Environmental & Forestry
Mining, Oil & Gas
Agriculture
Utilities & Construction
Transportation
Vehicle Security (Fleet Management)
Public Safety
Emergency Management, Search & Rescue
Crime Prevention
Timing & Synchronization
(banking, telecommunications)
LBS - Location Based Services
(cell phones, wireless web)
Advantages / Disadvantages
ADVANTAGES
Mobility
Global coverage
Weather independent
Day or Night
Accuracy
DISADVANTAGES
Requires clear view of sky
Ionospheric influences
Multi-path
- buildings, canyons, trees
- large, wet leaves
- large flat buildings
- chain link fences