In English

Evaluation of sea level sensors at the Onsala space observatory

Jonas Wahlbom
Göteborg : Chalmers tekniska högskola, 2015. 79 s.
[Examensarbete på avancerad nivå]

Abstract A rise of the global mean sea level by more than one metre by the year 2100 is expected. Measurements of the local sea level variations are important to understand the effect on a global scale. This report evaluate a new tide gauge installation at the Onsala Space Observatory with the aim to perform measurements at millimetre accuracy. The new tide gauge consist of two types of level sensors placed in a stilling well. A compact bubbler system and a pulsed radar where the compact bubbler system in the experimental setup consists of a total of five units of which two of the units are of a standard version with a nominal accuracy of 5 mm and three of them of an improved version (called USGS) with a nominal accuracy of 3 mm. Several indoor and field experiments were performed to evaluate the sensors in terms of accuracy, linearity, and stability. A new type of bubble chamber was constructed and compared to the original one. Systematic errors were found when the radar was placed in a narrow tube during the indoor experiments and tendencies of the same systematic error was found in the field experiment even though the tube in this case was significantly wider. A standard deviation of 2.5 mm was found in the differences between the USGS versions in the field environment and a standard deviation of 10 mm between the standard bubbler and the USGS version which was about the same standard deviation that was found between the USGS bubblers and the radar. An improvement was seen in the comparison between the standard bubbler unit and the radar were a standard deviation of 6.5 mm was found. The reason for the better agreement between the less accurate bubbler and the radar is believed to be the timing of the sampling units. The radar and standard bubbler uses the same logging unit and are therefore sampled at the same time. The comparison between the bubbler chambers did not result in any significant differences. This evaluation will serve as a valuable foundation to continued measurements and improvements of the new tide gauge.

Nyckelord: keywords: tide gauge, sea level, compact bubbler system, radar



Publikationen registrerades 2015-09-22. Den ändrades senast 2015-09-22

CPL ID: 222971

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