Olav Vestøl

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Release note for the BSCD2000 height transformation grid

The International Hydrographic Review

A unified Chart Datum for the whole Baltic Sea is required for the use of global navigation satel... more A unified Chart Datum for the whole Baltic Sea is required for the use of global navigation satellite systems (GNSS) in accurate 3-D bathymetric surveying and navigation, enabling for automated shipping with increased efficiency and improved maritime safety. So far, the zero levels of nautical maps were derived from the mean sea level (MSL) of different local tide gauges. The inherent height datum differences between neighboring map sheets are a fundamental infrastructural obstacle for implementing and using new cross-border navigation services based on electronic nautical maps. The Baltic Sea Hydrographic Commission, with its Chart Datum, Water Level and Currents Working Group (CDWCWG), has therefore decided to implement a harmonized vertical reference in the Baltic Sea (BSHC18 conference, 2013; Schwabe et al., 2020) called the Baltic Sea Chart Datum 2000 (BSCD2000). The first milestone was the agreement between the Baltic Sea countries on the fundamental standards of the BSCD2000,...

Dynamic reference frame on Iceland

EGU General Assembly Conference Abstracts, Apr 1, 2019

The Baltic Levelling Ring

Future height systems in the Nordic countries , their relation to the EVRS 2000 and to INSPIRE GIS standards by Working Group for Height Determination of the Nordic Geodetic Commission

Future height systems in the Nordic countries, their relation to the EVRS2000 and to INSPIRE GIS ... more Future height systems in the Nordic countries, their relation to the EVRS2000 and to INSPIRE GIS standards by Working Group for Height Determination of the Nordic Geodetic Commission Jaakko Mäkinen (Jaakko.Makinen@fgi.fi), Martin Lidberg, Klaus Schmidt, Mikko Takalo, Mikael Lilje, Karsten Engsager, Per-Ola Eriksson, Casper Jepsen, Per-Anders Olsson, Veikko Saaranen, Runar Svensson, and Olav Vestøl.

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Towards a dynamic reference frame in Iceland

There is a growing need for geodetic reference frames that on a national level support the increa... more There is a growing need for geodetic reference frames that on a national level support the increasing use of global positioning services. Today, the vast majority of countries have their own national reference frame. In Europe this frame is normally aligned to ETRS89. This system is co-moving with the Eurasian tectonic plate. Global Navigation Satellite Systems (GNSS) and global positioning services are normally aligned to the Earth as a whole through a global reference frame like ITRF2014. Consequently, global positioning services does not give direct access to the national reference frame without a timedependent transformation. A solution is to align the national reference frame directly to a global reference frame. In such a frame, the coordinates of a point fixed to the ground will change with time, a fact leading to the expression dynamic reference frame (DRF). To be prepared for future challenges, the Nordic Geodetic Commission (NKG) initiated a pilotproject on DRF in Iceland....

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NKG2016LU: a new land uplift model for Fennoscandia and the Baltic Region

Journal of Geodesy, 2019

We present the official land uplift model NKG2016LU of the Nordic Commission of Geodesy (NKG) for... more We present the official land uplift model NKG2016LU of the Nordic Commission of Geodesy (NKG) for northern Europe. The model was released in 2016 and covers an area from 49° to 75° latitude and 0° to 50° longitude. It shows a maximum absolute uplift of 10.3 mm/a near the city of Umeå in northern Sweden and a zero-line that follows the shores of Germany and Poland. The model replaces the NKG2005LU model from 2005. Since then, we have collected more data in the core areas of NKG2005LU, specifically in Norway, Sweden, Denmark and Finland, and included observations from the Baltic countries as well. Additionally, we have derived an underlying geophysical glacial isostatic adjustment (GIA) model within NKG as an integrated part of the NKG2016LU project. A major challenge is to estimate a realistic uncertainty grid for the model. We show how the errors in the observations and the underlying GIA model propagate through the calculations to the final uplift model. We find a standard error better than 0.25 mm/a for most of the area covered by precise levelling or uplift rates from Continuously Operating Reference Stations and up to 0.7 mm/a outside this area. As a check, we show that two different methods give approximately the same uncertainty estimates. We also estimate changes in the geoid and derive an alternative uplift model referring to this rising geoid. Using this latter model, the maximum uplift in Umeå reduces from 10.3 to 9.6 mm/a and with a similar reduction ratio elsewhere. When we compare this new NKG2016LU with the former NKG2005LU, we find the largest differences where the GIA model has the strongest influence, i.e. outside the area of geodetic observation. Here, the new model gives from -3 to 4 mm/a larger values. Within the observation area, similar differences reach -1.5 mm/a at the northernmost part of Norway and -1.0 mm/a at the north-western coast of Denmark, but generally within the range of -0.5 to 0.5 mm/a.

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Projected 21st Century Sea-Level Changes, Observed Sea Level Extremes, and Sea Level Allowances for Norway

Journal of Marine Science and Engineering, 2017

Changes to mean sea level and/or sea level extremes (e.g., storm surges) will lead to changes in ... more Changes to mean sea level and/or sea level extremes (e.g., storm surges) will lead to changes in coastal impacts. These changes represent a changing exposure or risk to our society. Here, we present 21st century sea-level projections for Norway largely based on the Fifth Assessment Report from the Intergovernmental Panel for Climate Change (IPCC AR5). An important component of past and present sea-level change in Norway is glacial isostatic adjustment. We therefore pay special attention to vertical land motion, which is constrained using new geodetic observations with improved spatial coverage and accuracies, and modelling work. Projected ensemble mean 21st century relative sea-level changes for Norway are, depending on location, from -0.10 to 0.30 m for emission scenario RCP2.6; 0.00 to 0.35 m for RCP 4.5; and 0.15 to 0.55 m for RCP8.5. For all RCPs, the projected ensemble mean indicates that the vast majority of the Norwegian coast will experience a rise in sea level. Norway's official return heights for extreme sea levels are estimated using the average conditional exceedance rate (ACER) method. We adapt an approach for calculating sea level allowances for use with the ACER method. All the allowances calculated give values above the projected ensemble mean Relative Sea Level (RSL) rise, i.e., to preserve the likelihood of flooding from extreme sea levels, a height increase above the most likely RSL rise should be used in planning. We also show that the likelihood of exceeding present-day return heights will dramatically increase with sea-level rise.

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Sea Level Change for Norway: Past and Present Observations and Projections to 2100

ABSTRACT

Innføring av nytt høydesystem i Norge

Future height systems in the Nordic countries, their relation to the EVRS2000 and to INSPIRE GIS standards

EUREF, Symposium of …, 2003

Summary We discuss the relationship of EVRS2000 and EVRF2000 to future national height systems in... more

To what extent is the present seismicity of Norway driven by post-glacial rebound?

Journal of the Geological Society, 2010

... To investigate the significance and possible extent of the shorter-wavelength crustal deforma... more

A continuous velocity field for Norway

Journal of Geodesy, 2012

In Norway, as in the rest of Fennoscandia, the process of Glacial Isostatic Adjustment causes ong... more In Norway, as in the rest of Fennoscandia, the process of Glacial Isostatic Adjustment causes ongoing crustal deformation. The vertical and horizontal movements of the Earth can be measured to a high degree of precision using GNSS. The Norwegian GNSS network has gradually been established since the early 1990s and today contains approximately 140 stations. The stations are established both for navigation purposes and for studies of geophysical processes. Only a few of these stations have been analyzed previously. We present new velocity estimates for the Norwegian GNSS network using the processing package GAMIT. We examine the relation between time-series length and precision. With approximately 3.5 years of data, we are able to reproduce the secular vertical rate with a precision of 0.5 mm/year. To establish a continuous crustal velocity field in areas where we have no GNSS receivers or the observation period is too short to obtain reliable results, either interpolation or modeling is required. We experiment with both approaches in this analysis by using (i) a statistical interpolation method called Kriging and (ii) a GIA forward model. In addition, we examine how our vertical velocity field solution is affected by the inclusion of data from repeated leveling. Results from our geophysical model give better estimates on the edge of the network, but inside the network the statistical interpolation method performs better. In general, we find that if we have less than 3.5 years of data for a GNSS station, the

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Determination of Postglacial Land Uplift in Fennoscandia from Leveling, Tide-gauges and Continuous GPS Stations using Least Squares Collocation

Journal of Geodesy, 2006

Precise leveling, tide-gauge recordings and time series from continuous GPS stations are all sour... more Precise leveling, tide-gauge recordings and time series from continuous GPS stations are all sources of information about the ongoing postglacial land uplift in Fennoscandia. This article describes how to gather these three sources of data together in a least-squares collocation adjustment in order to calculate uplift rates, as well as new heights for the benchmarks in the leveling network. The estimated reliability of the resulting uplift model is in general better than 0.4 mm/year, decreasing in areas of fewer data. A smoother and extended version of the land uplift model described here is used in the adjustment of the new height system in Sweden (RH 2000) under the name RH 2000 LU. Later on, the name was changed to NKG2005LU. The Finnish Geodetic Institute (FGI) has decided to use the same model when they calculate their new height system, N2000.

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NKG2020 transformation: An updated transformation between dynamic and static reference frames in the Nordic and Baltic countries

Journal of Geodetic Science

Coordinates in global reference frames are becoming more and more common in positioning whereas m... more Coordinates in global reference frames are becoming more and more common in positioning whereas most of the geospatial data are stored in registries in national reference frames. It is therefore essential to know the relation between global and national coordinates, i.e., the transformation, as accurately as possible. Officially provided pan-European transformations do not account for the special conditions in the Nordic and Baltic countries, namely crustal deformations caused by Glacial Isostatic Adjustment. Therefore, they do not fulfill the demands for the most accurate applications like long-term reference frame maintenance. Consequently, the Nordic Geodetic Commission (NKG) has developed customized and accurate transformations from the global ITRF to the national ETRS89 realizations for the Nordic and Baltic countries. We present the latest update, called the NKG2020 transformation, with several improvements and uncertainty estimates. We also discuss its significance and practi...

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