3:30 PM - 3:45 PM
[SGD02-07] Crustal deformation model to support high-level utilization of PPP - POS2JGD and its future perspectives -
Keywords:Crustal deformation correction, POS2JGD, GEONET, InSAR time series analysis, Data assimilation
Japan is located in a boundary zone of 4 tectonic plates, and one of areas where not only crustal deformation velocity but the strain rate are the largest in the world. This geophysical circumstance made a barrier to introduce GNSS surveying to maintain Japanese geodetic datum. A position error due to the strain cannot be neglected in long baseline observation like GNSS surveying in Japan, because the error of relative positioning is proportional to accumulated strain from the reference epoch of the geodetic datum to the observation epoch, and the observational baseline length. To address this problem, GSI of Japan (GSI) implemented semi-dynamic datum in 2010. An essential tool of this framework is a deformation model. The gridded model data are created from the coordinate difference between reference and observation epochs at national GNSS CORS. In GNSS surveying, it is applied to transform the coordinates at the reference epoch to an observation epoch at known points, and those at an observation epoch to the reference epoch at new points. To stably operate the modelling, a simple step function is adopted as a time function in the model, and the model has been updated once a year.
In these days, we see significant advances in satellite positioning techniques including precise point positioning (PPP) and the applications to various fields such as autonomous driving. For these PPP applications, consistency between positioning solutions and digital maps usually based on the reference epoch is important, and it is essential for the PPP users to apply the deformation model to transform positioning solutions from the observation epoch to the reference epoch. In this application, an absolute value of the deformation model is important. However, our investigation implies conventional model is not good enough to meet the required accuracy (up to a couple of cm). Thus GSI published the framework to support transformation for point positioning including PPP, POS2JGD, on 31 March, 2020 (https://positions.gsi.go.jp/cdcs/). In order to improve the accuracy, the model used in POS2JGD is more frequently updated (every 3 months). Considering a variety of uses, POS2JGD provides not only the deformation model but an online calculator and web API.
Towards improving more accurately the deformation model for POS2JGD, an approach to include a piecewise linear function as a time function is evaluated, and we saw the improvement on especially postseismic deformation of The 2011 off the Pacific Coast of Tohoku Earthquake (Tanaka et al., 2020). However, the evaluation using leveling data implies the GNSS-derived model cannot reproduce the deformation with shorter wavelength than the interval of GNSS CORS within the required accuracy (Yamashita et al., 2021). To address this issue, Yamashita et al.(2021) proposed utilization of InSAR time series analysis as well as GNSS CORS for the modelling. Advanced Land Observing Satellite-4 (ALOS-4) is timely scheduled to be launched in FY 2022. Utilization of highly frequent observation data by ALOS-4 is expected to enable more accurate deformation modelling. In order to implement these approaches into the operational modelling, we need investigations and evaluations on optimal data assimilation of GNSS CORS and InSAR time series analysis.
To conclude, GSI created POS2JGD to publish on the web by improving semi-dynamic framework for GNSS surveying. POS2JGD enables PPP users to have a direct access to Japanese geodetic datum, and to boost applications to various fields including autonomous driving. As for the future perspective, GSI will continuously develop the deformation model to improve POS2JGD as a geospatial infrastructure.
References
Tanaka et al.(2020): Towards sophistication of Crustal Deformation Correction System (POS2JGD), Geod. Soc. Japan.
Yamashita et al.(2021): Identification of vertical displacement in middle reaches of Tone River using GEONET and InSAR time series analysis data, Geod. Soc. Japan.
In these days, we see significant advances in satellite positioning techniques including precise point positioning (PPP) and the applications to various fields such as autonomous driving. For these PPP applications, consistency between positioning solutions and digital maps usually based on the reference epoch is important, and it is essential for the PPP users to apply the deformation model to transform positioning solutions from the observation epoch to the reference epoch. In this application, an absolute value of the deformation model is important. However, our investigation implies conventional model is not good enough to meet the required accuracy (up to a couple of cm). Thus GSI published the framework to support transformation for point positioning including PPP, POS2JGD, on 31 March, 2020 (https://positions.gsi.go.jp/cdcs/). In order to improve the accuracy, the model used in POS2JGD is more frequently updated (every 3 months). Considering a variety of uses, POS2JGD provides not only the deformation model but an online calculator and web API.
Towards improving more accurately the deformation model for POS2JGD, an approach to include a piecewise linear function as a time function is evaluated, and we saw the improvement on especially postseismic deformation of The 2011 off the Pacific Coast of Tohoku Earthquake (Tanaka et al., 2020). However, the evaluation using leveling data implies the GNSS-derived model cannot reproduce the deformation with shorter wavelength than the interval of GNSS CORS within the required accuracy (Yamashita et al., 2021). To address this issue, Yamashita et al.(2021) proposed utilization of InSAR time series analysis as well as GNSS CORS for the modelling. Advanced Land Observing Satellite-4 (ALOS-4) is timely scheduled to be launched in FY 2022. Utilization of highly frequent observation data by ALOS-4 is expected to enable more accurate deformation modelling. In order to implement these approaches into the operational modelling, we need investigations and evaluations on optimal data assimilation of GNSS CORS and InSAR time series analysis.
To conclude, GSI created POS2JGD to publish on the web by improving semi-dynamic framework for GNSS surveying. POS2JGD enables PPP users to have a direct access to Japanese geodetic datum, and to boost applications to various fields including autonomous driving. As for the future perspective, GSI will continuously develop the deformation model to improve POS2JGD as a geospatial infrastructure.
References
Tanaka et al.(2020): Towards sophistication of Crustal Deformation Correction System (POS2JGD), Geod. Soc. Japan.
Yamashita et al.(2021): Identification of vertical displacement in middle reaches of Tone River using GEONET and InSAR time series analysis data, Geod. Soc. Japan.