4. Geographic Coordinate System
• However, degrees are large so we split them for more refined
measurements….
Each degree is split into 60 parts, called minutes.
Each minute is split into 60 parts, called seconds.
• Degree/Mins/Secs:
40 08’ 22” N, 156 05’ 36” W
• Decimal Degrees:
40.1394, -156.0933
• GPS Coordinates:
40 8.36’ N, 156 5.6’ W
5. What is GPS?
Global Positioning System
• System of satellites (24+) for determining
positions on Earth
– Originally developed by the US Dept of Defense
– Not available to the general public until 2000
6. How does it work?: Trilateration
1000 km Boise
1110 km Minneapolis
990 km Tucson
7. How will we measure the distance?
• By using very precise time measurements
(nanosecond: 0.000000001 second)
Velocity x Time = Distance
Radio wave velocity = 186,000 miles/sec
9. Accuracy: how close a measurement is to the true value
Precision: the reproducibility of a measurement
Accuracy and Precision Accuracy only
Precision only Neither accuracy
nor precision
