Patent ID: 6819113
Filing Date: 2004-11-16
Classification: G01V

Abstract:
An apparatus for precision grid surveys comprising:a. at least one stationary unit comprising a light source unit for emitting a parallel laser beam; at least one rotator for projecting said parallel laser beam toward at least one photodetector and wherein said rotator rotates said parallel laser beam about a vertical axis such that said parallel laser beam sweeps in a horizontal plane at a steady angular frequency; b. at least one roving unit comprising a photodetector array for detecting when said parallel laser beam is incident on said at least one photodetector wherein said roving unit is moved about a survey location; c. said at least one stationary unit and said at least one roving unit further comprise a first and a second clock wherein said first clock is on said at least one roving unit and said second clock is on said stationary unit wherein said first and said second clocks are synchronized such that the time is measured when said light beam is incident on said at least one photodetector; means for measuring the magnitude of the terrestrial magnetic field in a two dimensional grid plane; means for measuring temporal field fluctuations where said measurement of the magnetic terrestrial field is corrected for temporal field fluctuation by measuring and subtracting the temporal field fluctuations and digital means for recording and storing the terrestrial magnetic field measurements and the temporal field fluctuation measurements.