THE GRAVITY METER AS A GEODETIC INSTRUMENT

Abstract

A special Worden temperature compensated gravity meter having a range of 5,500 mgals, and a reading sensitivity of 0.1 mgal was used to tie together various primary gravity base stations around the world and to establish new stations. Air transport was used and in a 3 month period over 80,000 miles were flown. Thirty‐three pendulum stations were reoccupied involving a change in gravity of 3,800 mgals, and 125 gravity stations were established. The investigation demonstrated that this instrument could be used satisfactorily for long range geodetic work and the results appear to be the equal of good pendulum observations. Drift was corrected for on the basis of the drift rate established immediately before and after flights. Closures after correcting for drift averaged less than 0.4 mgals, and the closure for the world girdling loop was 0.33 mgals. The probable error based upon the gravity values at the reoccupied pendulum station was ±0.5 mgals. Reoccupation of the absolute gravity stations at the U. S. Bureau of Standards in Washington, D. C. and the National Physical Laboratory in Teddington, England, indicated an approximate 5 mgal error in these pendulum determinations. Indirect ties to the absolute gravity base in Potsdam, Germany, through the primary national gravity bases tied to it, indicated a 15 to 19 mgal error in the Potsdam absolute value. Most of the primary national gravity bases tied directly to Potsdam were found to agree among themselves to within 1 mgal, and the U. S. Bureau of Standards Absolute Base in Washington, D. C. to have a perfect connection within the limits of accuracy of the present measurements. This investigation was made under the auspices of the Office of Naval Research.