Vertical connection - precise levelling
To connect tide-gauge readings with Continuous GPS (CGPS) and express them in a unified geocentric global terrestrial reference frame, precise levelling measurements was planned to be performed every-year connecting GPS reference bench-mark with Contact Points of both tide-gauge sensors (CP), Tide-Gauge Bench-Mark (TGBM) and other benchmarks of the 1st Order National Levelling Network located near Wladyslawowo harbour. After each Absolute Gravity (AG) measurements levelling connection with TGBM and GPS marker was also performed.
In Poland four national precise levelling campaigns of high precision were carried out up to now.
The first precise levelling was carried out in the years 1926-1937, the second one in 1947-1958, the third one in 1974-1982 and the last one in 1999-2003, which was finalized on the measurement level and preliminary adjustment.
- 1926 - 1937 (10046 km, connected to tide gauge in Gdynia, ref. surface: Normal Null)
- 1947 - 1958 (10500 km, connected to 7 polish tide gauges, ref. surface: Kronstadt, Catalogue 'Kronstadt-1960')
- 1974 - 1982 (17015 km, connected to 7 polish tide gauges, ref. surface: Kronstadt, Catalogue 'Kronstadt-1980')
- 1999 - 2003 (17516 km, connected to 7 polish tide gauges)
Wladyslawowo tide gauge station was measured during last three campaigns.
Apart from the above national-wide campaigns, several levelling measurements close to Wladyslawowo harbour were also performed untill now and the data as well as the results are stored in levelling data bases:
- precise levelling campaign near Wladyslawowo performed in 1997 for EUVN_97
- precise levelling campaign performed for ESEAS-RI in August 2003
- precise levelling campaign performed for ESEAS-RI in October 2004
- precise levelling campaign performed for ESEAS-RI in September 2005
|Fig. 1. Vertical connection of tide-gauge Contact Points (TG), GPS bench-mark (CGPS), absolute gravity marker (AG) and selected 1st-Order National Vertical Network Bench-Marks (BM) in Wladyslawowo, performed by means of precise levelling method for ESEAS-RI Project.
After each BSL GPS Campaign, levelling measurements were made between tide gauge bench mark, GPS marker and at least two bench marks in the harbour.
Before 2003 calibration of the water-level staff was made by means of technical levelling each 2 - 3 years, provided the staff is not demaged by a fish cutter, by accident, e. g. in storm weather. After each repair or exchange the tide rod is levelled.
After EUVN_97 GPS Campaign tide gauge in Wladyslawowo was connected to EUREF 0301 Rozewie station and fundamental bench-mark Leczyce using precise levelling technique.
It is planned to measure the height differences between TGBM, contact point and reference bench mark (TGPBM) more frequently and using precise instead of technical levelling.
From analysis of the precise levelling observation results mentioned above we can conclude that no significant vertical movement of the harbour quay was occured with respect to the 1st-Order National Levelling Network bench-marks located up to about 1 km inland.
||Last updated on: 2005-10-21