Lantmäteriet, The Swedish Mapping, Cadastral and Land Registration Authority, is responsible for the operation and maintenance of SWEPOS and SWEREF99 (the Swedish official reference frame) and therefore also responsible for control and verification of the data provided by the reference stations.
Clas-Göran Persson at Lantmäteriet has created a new controlling procedure, including software, to analyze the position uncertainties of the SWEPOS stations using various statistical methods. The software evaluates the daily calculated coordinate data of the stations subsequently; it will not be installed directly on the actual stations.
The primary goal is to study the stability of SWEPOS from a SWEREF 99 point of view, not to analyze SWEPOS real-time service. The controlling procedure is referred to as “the CGP Program”. The CGP Program is a toolbox of statistical methods created in MATLAB, determining standard deviation, correlation, distribution (outliers) and more. Its main purpose is to determine if the SWEPOS data consists of uniform uncorrelated normal distributed deviations, known as white noise, or not.
The purpose of my thesis is to; based on this new controlling procedure, create a graphical overview of the current status of the SWEPOS network for Lantmäteriet. Instead of making a thorough analysis of each station the maps created in this Thesis will visualize the outcome on an overall basis and identify the stations and areas of interest for further analysis.
Together with representatives from Lantmäteriet we decided that three different map types where of interest. All the maps were to be based on SWEPOS data from 2010, analyzed by the CGP program, and visualized on a nationwide basis. They differ in their cartographic appearance and they all describe different characteristics of the SWEPOS stations.
Conclusions from the maps and the numerical analyzes:
* There is a clear “winter effect”, most obvious in the height coordinate. Removal of the snow-period results in lower standard deviations and fewer unwanted systematic effects.
* The Northing coordinate has a slightly higher standard deviation than the Easting coordinate. The standard deviation in Height is around 50% larger than the horizontal standard deviation.
* There is no evidence for physical movements, when comparing the official SWEREF 99 coordinates with the 2010 positions.
Author: Bronder, Axel Viking