1. Secondary data sources
Primary data sources
Original: survey, interview, census, GPS
New findings from a project
Collected for a SPECIFIC STUDY
Secondary data sources
Archive data (Census, USGS, Google Earth, a history textbook, a review article)
The interpretation of primary data
Biography, movie review

2. Global Positioning System
Three Segments:
User segment (10s of millions)
Control segment (master control station(s))
Space segment (satellites)

3. Global Positioning System
User segment: For navigation, projectile guidance, search and rescue, survey, communications, time, recreation, tectonics, volcanoes…

4. Control segment (master control station(s)) NGA = National Geospatial-Intelligence Agency AFSCN =Air Force Satellite Control Network

5. The GPS Master Control Station, operated by the 50th Space Wing's 2nd Space Operations Squadron at Schriever AFB is responsible for monitoring and controlling the GPS satellite constellation.

6. Global Positioning System
Space Segment: US GPS satellites
Medium Earth Orbit
20,200 km (12,552 mi.)
12 hr. orbit
6 orbits; 4 satellites
each

7. Global Positioning System
Space Segment: US GPS satellites
63 in orbit
~30 ‘healthy’ and available, as of 9/21/2018
9 usually in view from any point
Not perfectly uniform orbits

8. ISS = 93 minutes

9. Global Positioning System
What’s next: ^ life expectancy, ^ accuracy
GPS Block IIF – #12 of #12 launched 2/5/16
GPS Block III (under development; Lockheed Martin; 2014 launch delayed to 2018, 3x more accurate)
$115M / satellite – 36 to be purchased (4.6B total)
Much more:

12. guaranteed in hostile situations.
GLONASS – Russia’s GPS (2010)
with GPS, allows 14 – 20 satellites!
BEIDOU – China’s GPS (2020)
IRNSS – India’s GPS (2015)
Galileo – Europe’s GPS (2020)
France, Japan under development
Access to US GPS not
guaranteed in hostile situations.

13. THE WHITE HOUSE Office of the Press Secretary For Immediate Release May 1, 2000 
STATEMENT BY THE PRESIDENT REGARDING THE UNITED STATES' DECISION TO STOP DEGRADING GLOBAL POSITIONING SYSTEM ACCURACY
Bill: Today, I am pleased to announce that the United States will stop the intentional degradation of the Global Positioning System (GPS) signals available to the public beginning at midnight tonight. We call this degradation feature Selective Availability. This means that civilian users of GPS will be able to pinpoint locations up to ten times more accurately than they do now.

14. Q: What happened?
A: Selective Availability was removed
MAY 1, MAY 3, 2000

15. Augmentation
systems improve
positioning
WAAS (FAA) 50 ref. stations in N. America & HI. correct GPS precision errors. 25 ft. accuracy!
CORS (NOAA) 19,000 stations,
mostly in U.S. For post-processing to cm accuracy.

17. A CORS tracking station

18. This is why you average waypoints

21. NEXT
ArcMap 10.6 demo
Hand out GIS homework sheet (10 questions, due in Canvas by Sunday, Oct. 30, 11:59pm)