GPS and MAPS

1
GPS and MAPS

• Why they are invaluable tools for everyone

2
The importance of maps

• Maps are the fundamental basis of the
  geo-sciences
• They communicate spatial data
• The biggest problem with maps is that they depict
  information from a round sphere onto a flat
  surface
• We need to be able to measure that

3
The Earth is divided in lines of latitude and
lines of longitude

• Latitude
• Lines that run parallel to each other and trend
  east-west around the globe
• Longitude
• Lines that run from pole to pole and trend
  north-south (NB these are not parallel to each
  other)

4
Some statistics on latitude

• Latitude is measured north and south of the
  equator in degrees
• Each degree of latitude 69 miles (based on a
  perfect sphere)
• Distance around the Earth from pole to pole is
  24,899 miles

90N
45N
90
45
0
45
90
45S
90S
5
(No Transcript)
6
Parallels of latitude
7
Some statistics on longitude

• Longitude is measured east and west of a line
  that runs through Greenwich, England (0)
• Runs from
• 0-180E
• 0-180W
• 180E and 180W are the same line

8
Some statistics on longitude
continued

• Longitude has no distance at the poles
• 1 of longitude has the longest distance at the
  equator
• The Earth is divided into 24 time zones along
  lines of longitude (with some deviations)
• Each time zone is 15 of longitude (with some
  deviations)

9
Meridians of longitude
10
The geographic grid
11
Using GPS to locate yourself on the geographic
grid
12
What is the Global Positioning System?
http//www.colorado.edu/geography/gcraft/notes/gps
/gps_f.html

• Department of Defense developed, worldwide,
  satellite-based radio navigation system
• Consists of 24 operational satellites
• Provides specially coded satellite signals that
  can be processed in a GPS receiver, enabling the
  receiver to compute position, velocity and time
• Four GPS satellite signals are used to compute
  positions in three dimensions and the time offset
  in the receiver clock

13
The GPS constellation
14
Satellites

• Each GPS satellite orbits the Earth twice a day
• Each satellite transmits signals to Earth
• GPS receivers measure the time between when
  satellites sent a signal relative to the GPS
  receiver receiving the signal
• Tells how far away the satellite is
• Signals from several satellites will give
  accurate results

15
GPS accuracy

• lt 1m to 15m depending on technology
• WAAS
• Wide area augmentation system
• Consists of 25 ground reference stations
  positioned across the United States that monitor
  GPS satellite data
• Only available in the USA
• Gives accuracy to within 5 ft

16
eTrex Venture GPS
Zoom buttons
Page button Scrolls between different screens
Find button
on/off
enter
Thumb stick