Your SlideShare is downloading. ×
Presentation On Gps
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×

Introducing the official SlideShare app

Stunning, full-screen experience for iPhone and Android

Text the download link to your phone

Standard text messaging rates apply

Presentation On Gps

2,016
views

Published on

G P S STANDS FOR GLOBAL POSITIONING SYSTEM........

G P S STANDS FOR GLOBAL POSITIONING SYSTEM........

Published in: Technology, Business

0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
2,016
On Slideshare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
74
Comments
0
Likes
0
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. AN INTRODUCTION TOGPS FOR GEOCACHERS
    PRESENTED BY :-
    TUHIN DAS
  • 2. WHAT IS GEOCACHING?
    “Geocaching is a sport where you use a multi billion dollar satellite system to locate rubbermaid containers in the middle of the woods.”
    - Anonymous
  • 3. GLOBAL POSITIONING SYSTEM (GPS)
    GPS was developed by US DoD and is managed by the US Air Force
    $750 million annual cost to operate
    Now widely used in the civilian sector as well as military users
    Surveying
    Geology
    Hiking
    Maritime
    Airlines
    And on and on…
  • 4. THREE SEGMENTS
    Space Segment
    Minimum of 24 satellites (currently 30) in orbit around Earth at altitude 20,000 km
    Control Segment
    Satellites are tracked by ground stations
    Navigation updates sent to satellites
    Updates ephemeris data (position) and atomic clocks
    User Segment
    GPS Receiver
    Uses data from satellites to calculate user’s position, altitude and other data
  • 5. TRANSMITTED SIGNALS
    Each satellite transmits:
    It’s approximate position
    Exact orbit and location
    Navigation signal
    Civilian
    Military (more precise)
  • 6. Your position
    The Simple View
    Knowing how far you are from at least three fixed positions, you can determine your position (triangulation)
    GPS Technology actually uses trilaterilization
  • 7. EXACT POSITION
    Using three satellites, you should be able to determine exact position but other factors prevent “prefect” overlap
    Atmospheric interference
    Buildings
    Trees, etc
    Using additional satellites, the GPSr attempts to reconcile position by adjusting the offsets
    Same “interference” for all signals
  • 8. POSITION ERROR
    Position (Uncertainty) Error
    GPSr will display uncertainty values
  • 9. OTHER DATA
    With multiple satellites can get altitude
    As you move, a GPSr will calculate
    Velocity
    Course
    Track (“bread crumbs”)
    Distance & Heading to marked position
    Elapsed time, average, speed, etc
  • 10. SELECTIVE AVAILABILITY & GEOCACHING
    Prior to May 2000, civilian GPS signal included a random error (Selective Availability)
    Civilian accuracy >30m
    Pres. Clinton turned off SA at 0000, 1 May 2000
    Resulted in accuracy < 10m
    Benefit sportsmen, FAA, etc
    3 May 2000 - Dave Ulmer placed first “cache”
    Now over 400,000 caches worldwide!
  • 11. TRANSMITTED SIGNALS
    Each satellite transmits ephemeris, almanac and navigation data
    Almanac data – coarse orbit & status info for all satellites
    Ephemeris – specific orbit and position data
    Navigation – Unique code every millisecond
    C/A (Coarse/Acquisition) – Civilian
    Encrypted P(Y) (Precision) - Military
  • 12. EXACT POSITION
    Using three satellites, you should be able to determine exact position but other factors prevent “prefect” overlap
    Atmospheric interference
    Buildings
    Trees, etc
    Using additional satellites, the GPSr attempts to reconcile position by adjusting the offsets
    Same “interference” for all signals
  • 13. BUT HOW DO YOU GET DISTANCE?
    Satellites have atomic clock
    GPSr has accurate internal clock
    Each satellite’s C/A code is a unique string
    Allows for reception of signals from multiple satellites on same frequency
    GPSr reproduces each C/A code internally
    GPSr “lines up” the two sequences, and based on the offset, you can determine distance to satellite
  • 14. COMPARING SEQUENCES
    GPSr Sequence
    Satellite Sequence
    Time Offset x Speed Of Light = Distance From Satellite
    Since you know the position of the satellite, and the distance from that satellite, you now have a sphere, centered on the satellite, you can be on