GPS and Geology

1
GPS and Geology

• Eric Helwig
• Jesse Storms

Marc AlbrechtUniv. of Nebraska at
KearneyDepartment of Biology
2
The Global Positioning System

• A constellation of 24 high-altitude satellites
• Cost over 12 billion US tax dollars

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GPS Satellites

• More than 24 up at all times.
• Three atomic clocks per satellites.
• Built to be resistant to blocking and jamming.
• Rockwell
• 11,000 miles
• 17 feet
• 1900 lbs.

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4 satellites for 3-D fix
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Relative Timing

• Each satellite sends out the same sequence of
  signals
• The receiver calculates the shift between
  identical parts of the code
• Analogy Stand on 20 yard line of stadium two
  friends yell to you from each goal line at the
  same moment.

Time difference
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GPS Uses

• Natural Resource based
• Animal/plant locations
• Soil/water sampling locations
• Human-based
• Air and sea navigation
• Emergency Services Locating
• Airplane landing systems
• Car-based direction services.

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Why is the system not perfect?

• Error sources
• Atmospheric
• Multipath scatter
• Positional error
• Dept. of Defense introduced error removed under
  Clinton
• Cheap GPS Units
• Limited satellite channels
• Poor internal processors.

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One solution Differential GPS

• This system uses two receivers to eliminate much
  of the signal error
• This increases accuracy to a few centimeters with
  good units.

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Two Types of GPS on Campus

• Garmin Handheld

• Trimble Survey TSC1

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Comparison

• Garmin Handheld

• Trimble Survey TSC1

• Cost 150-500 possibly more for special add-ons
• Come with preloaded base maps
• Excellent for personal travel
• Cannot capture precise locations 1-2m

• Cost 2,500
• Have nothing preloaded
• Useless for personal travel
• Can be very precise

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Where Does Geology Fit?