Investigations of geoid models in Finland - Towards GNSS-related height system

• Main Author: Saari, Timo
• Other Authors: National Land Survey of Finland, Maanmittauslaitos
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Aalto University 2023
• Subjects: Geoid; (quasi-)geoid model; GNSS; national height system; GOCE; GRACE; gravity; post-glacial rebound; Finland; Koivula; Saari; Fennoscandia
• Online Access: http://hdl.handle.net/10138/352467

Parts / Osajulkaisut: Publication 1: Saari, T., Poutanen, M., Saaranen, V., Kaartinen, H., Kukko, A., Nyberg, S. (2015). Height Determination Techniques for the Next National Height System of Finland - A Case Study. Geodesy and Cartography. 41(4):145–155. DOI:10.3846/20296991.2015.1120387 Publication 2: Saari, T., Bilker-Koivula, M. (2015). Evaluation of GOCE-based Global Geoid Models in Finnish Territory. Newton's Bulletin. 5:25–36. https://www.isgeoid.polimi.it/Newton/Newton_5/04_Saari_25_36.pdf Publication 3: Saari, T., Bilker-Koivula, M. (2017). Applying the GOCE-based GGMs for the quasi-geoid modelling of Finland. Journal of Applied Geodesy. 12(1):15–27. DOI:10.1515/jag-2017-0020 Publication 4: Saari, T., Bilker-Koivula, M., Koivula, H., Nordman, M., Häkli, P., Lahtinen, S. (2021). Validating Geoid Models with Marine GNSS Measurements, Sea Surface Models, and Additional Gravity Observations in the Gulf of Finland. Marine Geodesy. 44(3):196–214. DOI:10.1080/01490419.2021.1889727 In Fennoscandia, heights and their relations between each other are in constant change due to the post-glacial rebound, so the national height system needs to be updated occasionally. Traditionally, the update has been done with a method known as precise levelling, which is accurate but considered slow, laborious, and expensive. This dissertation studied the modern, mainly Global Navigation Satellite System (GNSS) -based, height determination techniques that could replace precise levelling as the method for the next national height system of Finland. GNSS-based techniques provide the height component relative to a reference ellipsoid, which is a mathematical surface and therefore lacks a physical connection to the Earth – i.e. have no information on the direction of water flow. Here, we need a (quasi-)geoid model to tie the ellipsoidal heights to the surface of the Earth and to national height systems. The (quasi-)geoid model's accuracy is therefore crucial with GNSS/geoid techniques. The presented case study gave us knowledge from ...