satellite ranges

GPS Notes Sheet
1. Global Positioning Systems:
2. ________________________________________________ satellites transmit signals while orbiting the Earth in a
precise pattern.
3. System comprised of three main components.
4. Any given time there are at least _____________________ satellites rotating in a distinct pattern at
approximately _________________________ miles above the earth.
5. Each satellite contains ___________________________________ accurate to _____________________________ of
error every ________________________________ year.
6. Key Point:
7. Ground Control Stations:
8. The control component is a _________________________ of ground control stations that continually track
and monitor the __________________________________ as they orbit the earth.
9. The control stations are located around the globe to maintain near constant contact with the
 The GPS network is primarily managed from _________________________________________________
near Colorado Springs.
 Locations:
10. Various Receivers:
i. Largest market used for recreational purposes
Mounted onboard receivers
i. In:
i. Construction/Engineering
11. Each satellite ________________________ a data message to the ___________________________ which include:
12. The time it takes the signal to reach the receiver allows the receiver to __________________________ the
distance to the _____________________________.
13. Using satellites, ________________________________ and __________________________________ can be identified
_____________________________ can be identified with a ___________________________ satellite.
14. GPS uses the process of __________________________________.
 Trilateration:
i. Unlike _________________________ which uses angle measurements and _______________
known distance to calculate the subject’s location, trilateration uses the know
locations of _________________ or more reference points, and the measured distance
between the subject and each reference point.
 To accurately find the exact location trilateration needs to have ___________________ known
reference points.
15. Example: Standing at B, you want to know your location relative to the reference points P1, P2,
and P3. Measuring r1 narrows your position down to a
circle. Next, measuring r2 narrows it down to two
points, A and B. A third measurement, r3, gives your
coordinates. A fourth measurement could also be made
to reduce error.
16. Many of today’s hand held GPS units have a standard
accuracy between ____________________ feet.
 With the utilization of an additional _______________________________________ you can move the
accuracy within inches.
 Using systems like this are called _______________________________________.
i. __________________________________ works by placing a GPS receiver or reference station
at a known ____________________________.
ii. Since the reference station knows its exact location, it can determine the
__________________________ in the satellite signals.
1. It does this by _______________________________ the ranges to each satellite using
the signals received and comparing these measured ranges to the actual
ranges calculated from its known position.
2. The difference between the _______________________________ and
______________________________ range for each satellite in view becomes a
3. The differential corrections are then applied to the GPS receiver’s
calculations, removing many of the common ___________________________ and
improving _______________________________________.
4. The level of accuracy obtained is directly related to the proximity,
_______________________________, and power of the
5. Typical DGPS accuracy is _____________________________________.
17. The cost of acquiring a _______________________ network can be very expensive and not possible for
the average consumer; however a public system known as the
_______________________________________________________________________________________ is available to the
 As of October 2007 there are _____________ WAAS towers, ________________________ in the
contiguous United States (CONUS), ____________________ in Alaska, _____________ in Hawaii,
_______________ in Puerto Rico, ______________ in Mexico, and __________________ in Canada.
 The WAAS towers are also augmented by ________________________________________.
 These satellites are known as the _______________________________________________________________.
i. It was implemented by the FAA (_________________________________________________) for
aviation users.
ii. Each reference station is linked to a master station, which puts together a correction
message and broadcasts it via satellite.
iii. Many ____________________________________ have WAAS capability including the Garmin
GPSmap 78s.
18. GPS was created and is operated by the ________________________________________________.
 The first satellite was launched in _______________________ and a full constellation of
_______________ satellites was completed in ___________________.
 The system, which was referred to as NAVSTAR, or the
______________________________________________________________________, became available to the
civilian population by an executive decree in the late _____________________ and in May of 2000
GPS became fully available to the public when the _________________________________________, or
intentional clock noise, was turned off.
19. Engineering:
20. Military:
21. Automotive/Aviation:
22. Outdoor Recreation:
23. Public Safety/Disaster Relief:
24. Agriculture:
 Field Guidance
1. Insect and weed infestations
2. Low yield
3. Soil characteristics
 Field Information Management
1. Yield
2. Application Rates
3. Infestations