Building a large-scale surface gravity network in Colombia using highly redundant measurements

Abstract This article presents a large-scale surface gravity network in Colombia, developed during a 3-year collaboration between Ohio State University (OSU) and Colombia’s national mapping agency, the Instituto Geográfico Agustín Codazzi . The network spans approximately one-third of the country’s surface area and consists of 498 stations, including 22 absolute gravity (AG) constraints. We applied the OSU field protocol and adjustment technique, extending it to address the challenge of traffic-induced noise at benchmarks located near major roads. Our methodology employed measurements with an unusually high degree of redundancy, with 87% of the gravity lines surveyed using a minimum of four relative gravimeters. Additionally, we utilized both automatic (Scintrex CG-6) and manual (LaCoste and Romberg Model G) instruments to leverage their complementary strengths in different environments. The resulting gravity values were determined with a typical uncertainty (1 sigma) of ± 0.03 mGal. The leave-one-out cross-validation tests using the AG stations demonstrated the robustness of our solution, with all residuals statistically indistinguishable from zero. Our findings show that the combination of enhanced observational redundancy and the use of multiple gravimeter types effectively mitigates measurement challenges under suboptimal conditions, with only a modest increase in field time.