Performance evaluation of multi-epoch airborne gravity surveys in Kalimantan, Indonesia

This study evaluates the performance of two multi-epoch airborne gravity surveys acquired over Kalimantan, Indonesia, during 2009–2010 (Data A) and 2021–2022 (Data B), using the LaCoste & Romberg Air/Sea S–99 (LCR S–99) and Canadian Micro Gravity GT–2A (CMG GT–2A) gravimeters, respectively. The analysis examines crossover consistency, repeatability, and spectral behaviour to quantify improvements in data quality and assess the feasibility of dataset integration. Prior to adjustment, Data A exhibited larger crossover discrepancies (Mean Absolute Error (MAE) = 5.628 mGal; Standard Deviation (STD) = 7.322 mGal), whereas Data B demonstrated improved internal consistency (MAE = 2.944 mGal; STD = 4.412 mGal). For the combined dataset before crossover adjustment, the statistics were MAE = 4.343 mGal and STD = 6.044 mGal. After aligning both datasets to the Data B reference frame, the order 0 crossover adjustment yielded the most stable solution, with statistical results of MAE = 2.927 mGal and STD = 4.262 mGal for Data A, MAE = 1.779 mGal and STD = 2.712 mGal for Data B, and MAE = 2.599 mGal and STD = 3.759 mGal for the combined dataset after crossover adjustment, effectively reducing systematic bias without introducing tilting artifacts. Flight segments exhibiting unstable or non-physical behaviour, identified through repeat-line consistency analysis, were discarded to maintain spatial integrity in the integrated product. A mean power spectral analysis, obtained by computing the power spectra along all repeat flight lines and averaging them to form representative spectral curves, confirms that both airborne datasets retain higher amplitudes than EGM2008 in the intermediate wavelength band of approximately $$0.7\text {--}7\,\textrm{km}$$ 0.7 -- 7 km , indicating enhanced sensitivity to intermediate- and short-wavelength gravity signals. Data B also shows a slower spectral decay, consistent with lower noise levels and stronger dynamic signal retention. Overall, the results demonstrate that a carefully adjusted and quality controlled integration of multi-epoch airborne gravity surveys can significantly improve internal consistency and spectral fidelity. The resulting dataset provides a reliable basis for regional geoid modelling and has strong potential to support broader geodetic and geophysical applications. Graphical abstract