5:15 PM - 7:15 PM
[SGD02-P03] Calculating new height at triangulation points with the revision of the national elevation results
Keywords:Revision of the national elevation results, JGD2024, Triangulation points, Mountain's height
In April 2025, Geospatial Information Authority of Japan (GSI) will revise the national elevation results, which is constructed by the new height system of Japan, "JGD2024" based on the Global Navigation Satellite Systems (GNSS) such as GPS and QZSS. The ellipsoidal height derived from the satellite positioning can be transformed to orthometric height, which is adopted in the current height system, by subtracting the geoid height. GSI has also developed a new precise gravimetric geoid model including the data obtained by the recent airborne gravity surveys, named "JPGEO2024". The new height system based on the satellite positioning and JPGEO2024 can eliminate the inconsistency of height caused by the accumulated crustal deformation and errors due to the conventional leveling survey. Furuya et al. (2024) determined the reference epoch of JGD2024 as June 1st 2024 considering the effects of annual variations derived from GNSS. In this presentation, we introduce the calculation method of new height at triangulation points based on the new heights of national GNSS CORS.
To revise the height of triangulation points, we construct transforming parameters for height as a gridded model with about 1km spacing using the same method of Kokado et al. (2014). To build the parameters, we calculate the height change from the current "JGD2011" to JGD2024. Firstly, we calculate the ellipsoidal height change in the two epochs (JGD2011 and JGD2024) at available 1313 GNSS CORS. Secondly, we construct the gridded model of ellipsoidal height change by applying Kriging interpolation. As for the geoid height, we convert the geoid model to about 1 km spacing by applying bilinear interpolation because it is provided as a gridded data with about 2 km spacing. By subtracting the geoid height data of the current "GSIGEO2011" from that of JPGEO2024, we obtain the gridded data of geoid height change. Finally, we obtain the transforming parameters for height for triangulation points by subtracting the gridded data of geoid height change from that of ellipsoidal height change. To calculate new height at each triangulation point, we firstly calculate the height change from the correction value of parameters at the nearest 4 grid points using bilinear interpolation. Secondly, we add the height change to the current height value. As a result, we obtain new height results for more than 100,000 triangulation points at all across Japan.
Distribution of ellipsoidal height change shows relatively large in the Tohoku region. The maximum change is about +70 cm around the Oshika Peninsula due to postseismic deformation of The 2011 off the Pacific Coast of Tohoku Earthquake. Distribution of geoid height change shows over +20 cm from northern Tohoku region to Hokkaido region. One reason is that GSIGEO2011, which is a hybrid geoid model fitted to GNSS/leveling geoid undulations, includes accumulated errors of leveling depending on the distance from the origin point at Tokyo. Distribution of transforming parameters for height is generally negative, while a part of the Tohoku region is positive. The average height change is about -13cm. In addition, at most of the triangulation points, the height change is within 40cm. On the other hand, the maximum positive height change is about +60 cm around the Oshika Peninsula. The maximum negative height change is about -70 cm around the Shiretoko Peninsula in Hokkaido region.
Furthermore, a lot of major mountain's heights in Japan are determined by the height of triangulation points. Hence, some of the mountain's heights change by 1 m due to the revision of height at triangulation points. As a future work, we are planning to evaluate the transforming parameters by the observed height using GNSS.
To revise the height of triangulation points, we construct transforming parameters for height as a gridded model with about 1km spacing using the same method of Kokado et al. (2014). To build the parameters, we calculate the height change from the current "JGD2011" to JGD2024. Firstly, we calculate the ellipsoidal height change in the two epochs (JGD2011 and JGD2024) at available 1313 GNSS CORS. Secondly, we construct the gridded model of ellipsoidal height change by applying Kriging interpolation. As for the geoid height, we convert the geoid model to about 1 km spacing by applying bilinear interpolation because it is provided as a gridded data with about 2 km spacing. By subtracting the geoid height data of the current "GSIGEO2011" from that of JPGEO2024, we obtain the gridded data of geoid height change. Finally, we obtain the transforming parameters for height for triangulation points by subtracting the gridded data of geoid height change from that of ellipsoidal height change. To calculate new height at each triangulation point, we firstly calculate the height change from the correction value of parameters at the nearest 4 grid points using bilinear interpolation. Secondly, we add the height change to the current height value. As a result, we obtain new height results for more than 100,000 triangulation points at all across Japan.
Distribution of ellipsoidal height change shows relatively large in the Tohoku region. The maximum change is about +70 cm around the Oshika Peninsula due to postseismic deformation of The 2011 off the Pacific Coast of Tohoku Earthquake. Distribution of geoid height change shows over +20 cm from northern Tohoku region to Hokkaido region. One reason is that GSIGEO2011, which is a hybrid geoid model fitted to GNSS/leveling geoid undulations, includes accumulated errors of leveling depending on the distance from the origin point at Tokyo. Distribution of transforming parameters for height is generally negative, while a part of the Tohoku region is positive. The average height change is about -13cm. In addition, at most of the triangulation points, the height change is within 40cm. On the other hand, the maximum positive height change is about +60 cm around the Oshika Peninsula. The maximum negative height change is about -70 cm around the Shiretoko Peninsula in Hokkaido region.
Furthermore, a lot of major mountain's heights in Japan are determined by the height of triangulation points. Hence, some of the mountain's heights change by 1 m due to the revision of height at triangulation points. As a future work, we are planning to evaluate the transforming parameters by the observed height using GNSS.