Indiana Gravity Base Network 1981

Abstract

"Values of absolute acceleration due to gravity have been obtained with a LaCoste and Romberg Model G gravimeter equipped with electronic capacitance readout for 106 base stations established in Indiana. Both written and graphic location descriptions have been recorded for each station for precise reoccupation. Base density is approximately one station per county. All stations have been tied and adjusted to International Gravity Bureau gravity bases in Louisville, KY., and Chicago, Ill., that are included in the International Gravity Standardization Net 1971 (IGSN-71).

Survey procedures and operational characteristics of the gravimeter have yielded a high internal consistency for the Indiana net. The maximum standard deviation for any one station is 0.02 mgal. Principal sources of error in the recorded base values are probably a function of unknown nonlinear characteristics of the gravimeter measuring screw and the values of the IGSN-71 stations to which the Indiana Gravity Base Network 1981 (IGBN-81) is adjusted. The accuracy of the gravity measurements is estimated to be within ±0.05 mgal.

Only a few selected base stations are listed in this report. Pertinent facts for each station in the IGBN-81 are on open file at the Indiana Geological and Water Survey."