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study of trees and how/where they grow
N, S, E, W
bearing is expressed
azimuth compass has degrees from...
contour lines, all points on line have...
section has how many acres
who created gps
gps system elements
satellites, receivers, ground stations, software
gps is used for
- navigating around the landscape
- mapping landscape features
normal constellation of satellites and current
- currently approx. 31
- six orbits, four satelites in each orbit
altitude and orbit of satellite
11,000 miles and 12 hour orbit
- five ground stations
- master control station in colorado springs
to find horizontal position you need
- at least three fixed objects
- knowing elevation requires a fourth
gps satelites broadcast signals
- L-band of microwave spectrum
- 186,000 miles/sec.
each satellite sends...
- ephemeris (own location)
- almanac (location of all others)
- signal indicating time sent
secret to gps is...
receivers do what?
calculate distance to each satellite based on time required for signal to arrive
3 types of signals
- coarse acquisition code- CA
- Carrier phase code- L1 & L2
- military- P code
errors of gps...
- multipath error
- selective availability
- receiver clock
- satellite clock
- ephemeris error
geometric dilution of position
- better solution when widely spaced satellites over cluster
- lower GDOP value better the position
- allows improved accuracy through collected data
- receiving signals from 2 sources to compare and give corrections
- removes all errors except multipath
- wide area augmentation system
- 25 ground stations administered by FAA
- only covers N. America
- transmits satellite corrections
accuracy of receivers
- recreation grade- 1-3 meters
- mapping grade- 1m or less
- survey- 1-5cm
- point with coordinates
- dynamic line following waypoints
- static multi reading points that create a track
latitude and longitude
- lat- E-W 180 degrees
- lon- N-S 0-90 degrees
- universal transverse mercator
- each zone has central meridian
- defines horizontal positions into 6 degree zones
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