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Geographic Information Systems. Global Positioning Systems (GPS). 1. GPS. A method used in surveying. It uses a constellation of satellites orbiting the earth at very high altitudes. GPS.

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Geographic information systems
Geographic Information Systems

Global Positioning Systems (GPS)


1 gps
1. GPS

  • A method used in surveying. It uses a constellation of satellites orbiting the earth at very high altitudes


GPS ..

  • The GPS technology allows accurate geodetic surveys by using specially designed receivers that, when positioned at a point on the earth, measure the distance from that point to three or more orbiting satellites

  • Through the geometric calculations of triangulation, the coordinates of the point on the surface of the earth are determined


X, Y, Z (position) and time from 4 satellites to calculate position

Pamela E. Jansma, University of Arkansas


2 navstar gps
2. NAVSTAR GPS position

  • NAVigation Satellite Timing And Ranging (NAVSTAR) Global Positioning System

  • Developed by U.S. Department of Defense

  • A constellation system of 28-30 satellites orbiting the earth at a high altitude twice a day

  • Transmitting precise time and position information

  • For world-wide and all weather navigations


Navstar
NAVSTAR .. position

  • 24 satellites in 6 orbital planes

  • Orbit the earth at approx. 20,200 km

  • 550 inclination

  • Satellites complete an orbit in approximately 12 hours

http://www.montana.edu/places/gps/lres357/assignments.html


http://www.colorado.edu/geography/gcraft/notes/gps/gps_f.htmlhttp://www.colorado.edu/geography/gcraft/notes/gps/gps_f.html


3 operation principles
3. Operation Principleshttp://www.colorado.edu/geography/gcraft/notes/gps/gps_f.html

  • The basis of GPS is triangulation

  • Satellite

  • GPS receiver

  • Determination of Location

  • Coordinate systems


3 operation distance to one satellite
3. Operation - Distance to One Satellitehttp://www.colorado.edu/geography/gcraft/notes/gps/gps_f.html

  • Satellite

    - continuously broadcasts time and its location

  • GPS receiver

    - receives the signal and calculates the distance between the satellite and the receiver:

    Distance = Velocity x Time

    where time = the time a signal takes to travel from the satellite to the receiver, velocity = ?


3 operation determine location
3. Operation - Determine Locationhttp://www.colorado.edu/geography/gcraft/notes/gps/gps_f.html

  • Determination of location

    - 3 or more simultaneous distance measurements are needed to determine the location of the receiver

  • Coordinate systems

    - A GPS provides its position in geographical/UTM/ State Plane coordinates and altitude


One measurement narrows down our position to the surface of a sphere
One measurement narrows down our position to the surface of a sphere

http://www.montana.edu/places/gps/lres357/assignments.html


A second measurement narrows down our position to the intersection of two spheres which is a circle
A second measurement narrows down our position to the intersection of two spheres, which is a circle

http://www.montana.edu/places/gps/lres357/assignments.html


A third measurement narrows down our position to just two points, because the intersection of a circle and a sphere is two points

http://www.montana.edu/places/gps/lres357/assignments.html


A four measurement narrows our position down to one point
A four measurement narrows our position down to one point points, because the intersection of a circle and a sphere is two points

http://www.bbk.ac.uk/geog/study/courses/pgis/GPSlecture10.pdf


3 operation determine location1
3. Operation- Determine location .. points, because the intersection of a circle and a sphere is two points

Pamela E. Jansma, University of Arkansas


4 gps receiver
4. GPS Receiver points, because the intersection of a circle and a sphere is two points

  • GPS receivers can be hand carried out or installed on aircraft, ships, tanks, submarines, cars and trucks


Gps receiver
GPS Receiver .. points, because the intersection of a circle and a sphere is two points

  • Radio channels

  • Internal clock

  • Computer


Gps receiver1
GPS Receiver .. points, because the intersection of a circle and a sphere is two points

  • Radio channels

    It needs one or more channels to receive signals of

        (1) the time a signal is sent, and        

    (2) a pseudorandom code to identify the signal

  • Internal clock

    - Synchronized with the satellite in order to calculate the signal travel time precisely


Gps receiver2
GPS Receiver .. points, because the intersection of a circle and a sphere is two points

  • Computer

    - Calculates distance and location

    - Stores location readings

    - Calculates the satellite availability


5 autonomous vs differential gps
5. Autonomous vs. Differential GPS points, because the intersection of a circle and a sphere is two points

  • Autonomous GPS: one receiver unit

  • Selective availability interference

  • Differential GPS

  • WAAS (Wide Area Augmentation System)


Differential gps
Differential GPS .. points, because the intersection of a circle and a sphere is two points

  • Selective availability interference

    -The Us government used to insert random errors in the signals in order to maintain optimum military effectiveness of the system. It was turned off in 2000

  • Differential GPS


Differential gps1
Differential GPS points, because the intersection of a circle and a sphere is two points

  • Selective availability interference

  • Differential GPS

    - Uses two receiver units, with one placed at a known location, such as a surveyed control point, to detect the inserted errors and calculate the needed corrections. The correction information is used by another receiver to overcome its selective availability interference


Differential gps dgps
Differential GPS (DGPS) .. points, because the intersection of a circle and a sphere is two points

  • The DGPS corrections can be applied to the GPS data in real-time (radio modems). Or, can be done later on a PC

  • There are a series of radio beacons to transmit the DGPS corrections for accurate navigation


5. Differential Correction points, because the intersection of a circle and a sphere is two points

http://www.bbk.ac.uk/geog/study/courses/pgis/GPSlecture10.pdf


5 dgps waas satellite dgps
5. DGPS - WAAS Satellite DGPS points, because the intersection of a circle and a sphere is two points

  • Wide Area Augmentation System (WAAS)

      - a real-time differential correction service

    - is based on a network of approximately 25 ground reference stations that cover a very large service area

http://www.montana.edu/places/gps/lres357/assignments.html


Waas satellite dgps
WAAS Satellite DGPS .. points, because the intersection of a circle and a sphere is two points

- Signals from GPS satellites are received by wide area ground reference stations (WRSs)

- Each of these precisely surveyed reference stations receive GPS signals and determine if any errors exist

- These WRSs are linked to form the U.S. WAAS network. This service is primarily for aviation purposes


Waas satellite dgps1
WAAS Satellite DGPS .. points, because the intersection of a circle and a sphere is two points

  • Improves the accuracy, integrity and availability of the basic GPS signals

  • Safety - critical navigation system for aviation

  • Owned and operated by Federal Aviation Administration (FAA)

  • Type: real-time

  • Cost: free


WAAS Stations points, because the intersection of a circle and a sphere is two points

http://www.montana.edu/places/gps/lres357/assignments.html


DGPS .. points, because the intersection of a circle and a sphere is two points

  • Omnistar

  • Type: Real-time

    - Network of reference stations

    70 reference stations

    3 network control centers

    - Worldwide coverage

  • Cost: ~ $800/year

http://www.montana.edu/places/gps/lres357/assignments.html


6 static vs kinematic gps
6. Static vs. Kinematic GPS points, because the intersection of a circle and a sphere is two points

  • Static: two or more receivers receive data for a lengthy period of time at a fixed location

  • Kinematic: one receiver is placed at a known location, while one or more receivers move from point to point

  • Real Time Kinematic (RTK)


7 advantages and limitations
7. Advantages and Limitations points, because the intersection of a circle and a sphere is two points

  • Advantages: fast, more accurate, lower cost than manual approaches

  • Disadvantages: obstructed locations


8 readings
8. Readings points, because the intersection of a circle and a sphere is two points

  • Chapter 2


Omnistar how it works
Omnistar – How it Works points, because the intersection of a circle and a sphere is two points

http://www.montana.edu/places/gps/lres357/assignments.html


http://www.colorado.edu/geography/gcraft/notes/gps/gps_f.htmlhttp://www.colorado.edu/geography/gcraft/notes/gps/gps_f.html


http://www.colorado.edu/geography/gcraft/notes/gps/gps_f.htmlhttp://www.colorado.edu/geography/gcraft/notes/gps/gps_f.html


5 dgps omnistar coverage north america
5. DGPS - Omnistar Coveragehttp://www.colorado.edu/geography/gcraft/notes/gps/gps_f.htmlNorth America

http://www.montana.edu/places/gps/lres357/assignments.html


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