Global positioning system
Upcoming SlideShare
Loading in...5
×
 

Global positioning system

on

  • 398 views

 

Statistics

Views

Total Views
398
Views on SlideShare
398
Embed Views
0

Actions

Likes
0
Downloads
1
Comments
0

0 Embeds 0

No embeds

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

Global positioning system Global positioning system Presentation Transcript

  • Global Positioning System (GPS) Satellite Location  20 Satellites in system  Each carries very accurate clock  Sends a coded signal every millisecond Ground Stations  Track satellite locations  Send signals to satellites to correct errors
  • Local Receivers Generate same signals as satellite  Compare differences to determine distance to satellite  Clocks not nearly as accurate  Some errors occur
  • GPS Location Location found by comparing signals  Time Difference x Light Speed = Distance  Clocks accurate to nanosecond (1 x 10-9 s)  Accuracy = (186,282 mi/s)(5280 ft/mi)(1 x 10-9 s) = 0.984 ft How do we locate to the cm?
  • Multiple Satellites One – distance only Two – point falls on a circle Three – one of two points 4 or more – average to eliminate error
  • Who Uses GPS? Surveyors Military Agriculture Railroads Corporate fleets Auto Security
  • Where Are We? Longitude  Starts at Greenwich  180° E or W Longitude  Starts at Equator  90° N or S Moorhead  N 46°52’ Latitude, W 96°45’ Longitude
  • Convert to Grid Projections  Lambert’s Conformal  Transverse Mercator  GPS uses UTM Error limited to 1:10,000 Computer models convert Lat, Long to universal grid
  • Sources of Error Atmospheric  Built-in Compensation Receivers  More satellites, better averaging Selective Availability  Intentional Error – DOD  Same error at any given time  Eliminate by differential positioning
  • Relative Positioning Dynamic  Two receivers, one set over known  Both collect data over time  Computer determines correction after Real-time Kinetic  Permanent receiver over know  Transmit real-time corrections to field  Farmers, transit authorities
  • PDOP Position Dilution of Precision Numeric scale indicating precision  Depends on position, number of satellites  Satellite alignment could limit precision PDOP = 1: Best precision PDOP = 5: Very poor – try later