CG3TOOL: an interactive computer program to process Scintrex CG-3/3M gravity data for high-resolution applications

Abstract

A newly developed interactive computer program, CG3TOOL, has been dedicated to the processing of the gravity data acquired by the Scintrex CG-3/3M automated gravity meter. The aim of CG3TOOL is two fold: to allow for an objective evaluation of Scintrex data and to provide a higher resolution in data reductions than those computed in real time by the microprocessor-controlled instrument. The program reads the gravity data acquired in either field or cycle mode (field surveys and continuous recordings, respectively) and then downloaded from the meter to a PC computer. The processing tasks are divided into two successive levels. Level 1 is dedicated to the reduction of the daily data files by applying standard or accurate corrections (earth tide, instrumental drift, atmospheric pressure). The precise corrections are performed up to the microGal (μGal) level, in accordance with the specifications of high-resolution surveys. Level 2 contains a series of processing tools (including network adjustment, anomaly computation, and gravity meter calibration) that will precisely compute and adjust the gravity values with error estimates. The interactive procedures and the program output (plot and text files) have been designed to ease data handling and archiving as well as to provide useful information for future purposes of data interpretation or modeling. CG3TOOL was developed in a standard C language for Unix Sun workstations and uses the standard graphical and mathematical Generic Mapping Tools (GMT) free library, available from the web. The objectives and principles of the computer program are presented below along with corresponding examples of the main processing tasks applied to observed data.