Measuring the Environment

Measuring the Environment

1. Geophysics Measurement

   • Electrical Resistivity Measurement
     • Detects subsurface layers
     • Electrical resIstance R=V/I
       • Electrical resistivity, p. R=p(l/A)
         • Compare to table of material's resistivity
   • Seismic Refraction
     • detects layer structure of the Earth
     • Small explosion
       • Measure time for each wave to reach geophone
   • Seismic Relection
     • Detects subsurface structures
     • Set off an explosion
       • Measure time for reflections of deep objects
   • Gravitational Geophysics
     • Detects subsurface structures
     • Uses a gravimeter to measure small changes in g, acceleration due to gravity
       • Absolute gravimeter measures speed and acceleration of falling weight in a vacuum
       • Relative gravimeter uses a spring to measure how extension changes
       • Dense subsurface objects increase g slightly
   • Magnetic Geophysical Methods
     • Near surface magnetic structures

2. LIDAR

   • Light Detection and Ranging
   • Measures profile of the EARTH
     • Sends a pulse of light and measures time for return pulse
     • Used to measure atmospheric properties
       • Height
       • Layering and density of clouds
       • Cloud particle properties
       • Temperature
       • Pressure
       • Wind
       • Humidity
       • Trace gas concentration
   • Components of LIDAR
     • Photodetector
       • Device that records the returning signal
     • Electronics
       • Processes signal
     • Computer
       • Produces image
   • Doppler LIDAR
     • Light scattered off of moving particles
     • Frequency shift is proportional to speed of moving particles
     • Gives wind speed

3. Satellite Environmental Sensing

   • Satelite imaging
   • Weather satellites
   • Satellite radar