Patent ID: 8061050

Claim:
A hydrostatic sensor device for measuring below-ground elevation changes of a grade comprising: an extensible hose or other flexible conduit filled with a fluid of constant density; a pressure transducer provided at one end of the hose for sensing differential changes in fluid pressure at said one end relative to a reference end at a given elevation; a differential pressure readout device provided at an opposite end of the hose for providing differential pressure readings of fluid pressure sensed by said pressure transducer compared to the reference end at the opposite end of the hose which is maintained at a reference atmospheric pressure, an electronic communication line coupled to and extending along the hose for electronically connecting said pressure transducer to said differential pressure readout device; and a hose reel mechanism for reeling in the hose and pulling said pressure transducer at the one end of the hose along a grade; wherein said pressure transducer at the one end of the hose is can be moved along a grade below ground, and differential pressure changes are measured by said pressure transducer end corresponding to elevation changes of the grade relative to the reference end.