Abstract
Airborne gravimetry with strapdown inertial sensors has been a valuable tool for many years to fill in the gravity data gaps on the areas not accessible by land. Accuracies of 1 mGal level with off-the-shelf navigation-grade inertial measurement units (IMU) can only be achieved provided that the accelerometer drifts mainly caused by the temperature variations inside the IMU housing are separated from the gravity signal. Although there are several strategies proposed in the literature to deal with this inseparability problem, we use a thermal stabilization system (iTempStab) added on an iNAT-RQH navigation-grade IMU and investigate its performance over a test region in central Turkey with moderate topography and highly qualified ground truth gravity data. Two test flights were performed in 2017 and 2018 with and without iTempStab add-on following almost the same flight trajectories. During the first flight in 2017 with iNAT-RQH only, which lasted almost 5.5 h, there were considerable temperature variations inside the IMU housing from 39.1 to 46.0 °C. A simple thermal correction based on a laboratory calibration done before the flight was applied to the vertical Z-accelerometer in the pre-processing stage. However, temperature changes were within 0.1 °C during the second test flight in 2018 with TempStab add-on. The temperature stabilization gained by the iTempStab add-on produced better cross-over statistics. While the RMSE of the non-adjusted cross-over residuals was about 2.6 mGal, it reduced by 50% with iTempStab add-on. The adjusted cross-over differences of the 2018 flight yielded an RMSE of about 0.5 mGal, which is a remarkable precision for the strapdown gravimetry. The comparison with upward continued ground gravity data at flight altitudes suggests that the thermal stabilization system shows also remarkable improvements in the residual statistics. The range of the residuals decreases from ± 10 to ± 5 mGal, the standard deviation decreases from 2.19 to 0.94 mGal, and the RMSE decreases from 2.24 to 1.48 mGal, respectively, with the iTempStab add-on. It can be concluded that the thermal stabilization system significantly improves the accelerometer stability and therefore the precision and accuracy of the strapdown airborne gravity estimates.
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Data availability
The data that support the findings of this study are owned by the Ministry of National Defense, General Directorate of Mapping, Turkey. Authors are not authorized to share the data with third parties. To access the data, contact the General Directorate of Mapping at gdm@harita.gov.tr.
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Acknowledgements
This work is a part of the Turkish Height System Modernization and Gravity Recovery Project supported by the Presidency of Turkey, Directorate of Strategy and Budget and coordinated by the General Directorate of Mapping. We would like to give our sincere thanks to TÜBİTAK National Metrology Institute in Gebze for their valuable contribution during the procurement of iNAT-RQH and iTempStab.
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All the authors contributed to the design of the study and came up with the idea of the research. MS processed the SIMU and GNSS data with the help of DB. HY performed upward continuation of terrestrial gravity data. MH is the project manager of iTempStab. MS drafted the manuscript. All authors read and approved the final manuscript.
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Simav, M., Becker, D., Yildiz, H. et al. Impact of temperature stabilization on the strapdown airborne gravimetry: a case study in Central Turkey. J Geod 94, 41 (2020). https://doi.org/10.1007/s00190-020-01369-5
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DOI: https://doi.org/10.1007/s00190-020-01369-5