Decorrelating Measured Airborne Gravity Gradiometry Data With Topography
Des FitzGerald and Rod Paterson and Asbjorn Christensen
Event name: 12th International Congress of the Brazilian Geophysical Society
Session: Gravity & Magnetics
Publication date: 15 August 2011
Info: Extended abstract, PDF ( 260.64Kb )
When there is rugged terrain and you wish to directly detect anomalously dense near surface ore-bodies such as VOC copper/nickel, use is being made of low-flying draped gravity gradiometry surveys. The geophysical signal collected is dominated by the topography response. Depending upon how many independent components are collected, a method is devised to quickly decorrelate the topographic signal, leaving a residual anomaly that shows the buried bodies. The resolving power of existing gradiometer systems approaches what is necessary for minerals applications, provided the best possible care is taken with processing, gridding and data reduction. Typically, 200m wavelength low pass filtering is applied to airborne gravity gradiometer data by the contractors. Predicted average surface density maps are created in this rapid process, which can be inspected and then used to judge how to control the decorrelation with terrain in selected areas of interest to the explorer. Existing surficial density anomalies, such as dumps, water filled pits and hills are identified and removed allowing the explorer to focus on the unexplained potentially more prospective anomalies.