9:30 AM - 9:45 AM
[SGD01-13] Publication of airborne gravity data, JGSN2016 land gravity data and gravity anomaly grid
Keywords:gravity, airbone gravity survey, JGSN2016, gravity anomaly, geoid
The Geospatial Information Authority of Japan (GSI) has conducted gravity survey all over Japan for providing standard gravity values. The gravity values are widely used for various social activities, such as development of geoid model which is used for height reference, calibration of weighing instruments, and exploration of underground structures.
Recently, satellite positioning technology has shown significant progress, and a precise geoid model required for height determination by satellite positioning becomes more important. So, GSI conducted airborne gravity survey and developed JGSN2016 land gravity data for developing a new precise gravimetric geoid model. We also developed gravity anomaly grid all over Japan. As of January 2024, we plan to release airborne gravity data, JGSN2016 land gravity data, and gravity anomaly grid in FY2023. We will report on the details and evaluation of these data.
The airborne gravity data are gravity values obtained by flights at altitudes between 1,500 and 5,000 m over Japan except for some remote islands from FY2019 to FY2023. The precision of the airborne gravity data is approximately 0.9 mGal as evaluated by crossover analysis. The accuracy of the data is approximately 1.5 mGal as evaluated by comparing with surface gravity data, such as land and shipborne gravity data and altimetry-derived marine gravity model.
The JGSN2016 land gravity data consists of two types of data. The first is the gravity values of about 13,000 second-order gravity stations according to the Japan Gravity Standardization Net 1975 converted to be consistent with the Japan Gravity Standardization Net 2016 (JGSN2016). The accuracy of the conversion was approximately 0.04 mGal as evaluated by leave-one-out cross-validation. The second is the gravity values obtained from the land gravity measurements conducted from FY2021 to FY2023 on remote islands where airborne gravity survey has not been conducted, and in areas where there is a vacuum of gravity data on land. The survey was conducted at approximately 600 points, with a tolerance of 0.1 mGal for inter-instrument range due to multiple instruments.
We used the three-dimensional least-squares collocation method (3D-LSC; Forsberg 1987) to create the gravity anomaly grid from the airborne gravity data, land gravity data, and altimetry-derived global marine gravity model. This data is used not only for the calculation of a new precise gravimetric geoid model, but also for the Estimated Gravity Value Calculation Websites, which is scheduled to be released in FY2023. This website estimates the gravity value at any given point from grid of simple Bouguer gravity anomaly. The difference between the measured and estimated values at the JGSN2016 gravity station was 1-2 mGal in standard deviation.
Recently, satellite positioning technology has shown significant progress, and a precise geoid model required for height determination by satellite positioning becomes more important. So, GSI conducted airborne gravity survey and developed JGSN2016 land gravity data for developing a new precise gravimetric geoid model. We also developed gravity anomaly grid all over Japan. As of January 2024, we plan to release airborne gravity data, JGSN2016 land gravity data, and gravity anomaly grid in FY2023. We will report on the details and evaluation of these data.
The airborne gravity data are gravity values obtained by flights at altitudes between 1,500 and 5,000 m over Japan except for some remote islands from FY2019 to FY2023. The precision of the airborne gravity data is approximately 0.9 mGal as evaluated by crossover analysis. The accuracy of the data is approximately 1.5 mGal as evaluated by comparing with surface gravity data, such as land and shipborne gravity data and altimetry-derived marine gravity model.
The JGSN2016 land gravity data consists of two types of data. The first is the gravity values of about 13,000 second-order gravity stations according to the Japan Gravity Standardization Net 1975 converted to be consistent with the Japan Gravity Standardization Net 2016 (JGSN2016). The accuracy of the conversion was approximately 0.04 mGal as evaluated by leave-one-out cross-validation. The second is the gravity values obtained from the land gravity measurements conducted from FY2021 to FY2023 on remote islands where airborne gravity survey has not been conducted, and in areas where there is a vacuum of gravity data on land. The survey was conducted at approximately 600 points, with a tolerance of 0.1 mGal for inter-instrument range due to multiple instruments.
We used the three-dimensional least-squares collocation method (3D-LSC; Forsberg 1987) to create the gravity anomaly grid from the airborne gravity data, land gravity data, and altimetry-derived global marine gravity model. This data is used not only for the calculation of a new precise gravimetric geoid model, but also for the Estimated Gravity Value Calculation Websites, which is scheduled to be released in FY2023. This website estimates the gravity value at any given point from grid of simple Bouguer gravity anomaly. The difference between the measured and estimated values at the JGSN2016 gravity station was 1-2 mGal in standard deviation.