Loading in 5 sec....

Geographic Information SystemsPowerPoint Presentation

Geographic Information Systems

- 121 Views
- Uploaded on

Download Presentation
## PowerPoint Slideshow about ' Geographic Information Systems' - jovita

**An Image/Link below is provided (as is) to download presentation**

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

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 ..

- 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 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 .. 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 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 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 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

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

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

Pamela E. Jansma, University of Arkansas

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

- Radio channels
- Internal clock
- Computer

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

- Chapter 2

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 Coveragehttp://www.colorado.edu/geography/gcraft/notes/gps/gps_f.htmlNorth America

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

Download Presentation

Connecting to Server..