Preliminary Adjustments for Establishment of the Lagos Gravity Network (LAGGNET) 017

Abstract

Preliminary adjustments for the establishment of the Lagos gravity network (LAGGNET) is herein presented. A gravity network is highly required for proper definition of a regional height system and also geophysical exploration activities. Horizontal control reliability test for the proposed network has been done using the Gauss Marcov functional model in a single constrained network with observation equations formed from the vector of baselenghts. Also the drift rate, atmospheric pressure corrections and latitude corrections have also been computed within the study area along an observation baseline called the Yaba – onipanu calibration line comprising of 4 control points within a total observation time of 77mins. The standard error of horizontal positions within the control network was found to be ±0.0051𝑚. The drift rate of the gravimeter was found to be 0.0007mgals/min and atmospheric pressure correction values between -0.009 to 0.027mgals were obtained. Insignificant latitude correction was observed due to the near-equatorial nature of the study area.