TidalTidal workwork atat thethe NorwegianNorwegian HydrographicHydrographic ServiceService

1st meeting in IHO-TWLWG Rio de Janeiro 2009

Tor Tørresen Norwegian Mapping Authority Hydrograpic Service HowHow wewe areare organisedorganised

„ The Norwegian Hydrographic Service (NHS) is a division in the Norwegian Mapping Authority.

„ Other divisions are the Geodetic Institute and the Land Mapping Service. TidalTidal workwork inin thethe NHSNHS

„ Run a network of 23 tide gauges „ Quality control of the data „ Drifting a tidal database „ Analyse the data „ Calculate tidal predictions and produce tide tables „ Distribute tidal data and tidal information TheThe NorwegianNorwegian tidetide gaugegauge networknetwork DifferencesDifferences inin tidaltidal rangerange

Tromsø 3 Honningsvåg ] Vardø 2 Hammerfest 1 Tromsø 0 51015202630 Vardø Kabelvåg 3 2 Rørvik Bodø 3 1 2 ] 0 1 51015202630 Rørvik 0 51015202630 Heimsjø Kristiansund Trondheim Ålesund Måløy

3 Bergen Bergen 2 Oslo 1 Oscarsborg 3 Stavanger Oslo 0 Helgeroa Viker 2 51015202630 3 Tregde 1 2 Stavanger 0 51015202630 1 0 51015202630 DataData flowflow

Filtering and Sutron quality control Optical encoder 8210 Database

Counterweight Float

Level switch Web

Copper cone Electronic Chart Display and Information System (ECDIS) Bronze plug TideTide gaugegauge atat TregdeTregde StillingStilling wellwell andand datadata loggerlogger

Digital encoder

Chain Sutron 8210 Contact point

Modem

Air pressure sensor RadarRadar TideTide GaugeGauge OldOld andand newnew systemsystem ProjectsProjects

„ Automatic quality control of water level data „ Mean Sea Surface at the Norwegian Coast. „ Tidal model for the North Sea, the Norwegian Sea and the Barents Sea. „ Improving the web-pages http://vannstand.statkart.no „ Mareano AutomaticAutomatic QualityQuality controlcontrol

„ Is required if the data will be used in near real time. „ The program must be able to find constant values, gaps, spikes and jumps. „ False values must be removed and gaps interpolated (if possible). „ Changes made to the data must be “flagged”. „ Bad data must not be published. CloseClose upup ofof partpart ofof thethe seriesseries

Stavanger, 27.May.2005 (3 hours), 1-minute values 0.78

0.76

0.74 Original 1-minute 0.72 values

0.7

0.68

0.66 Filtered

Water Level [m] values 0.64

0.62

0.6 21:00 22:00 23:00 00:00 Time WaterWater levellevel observationsobservations withwith 1010 minuteminute intervalsintervals

The sensor is sampled every second for three minutes and the average is calculated.

We see a lot of noise, but is it noise?. WaterWater levellevel observationsobservations withwith 11 andand 1010 minuteminute intervalsintervals

The 1 minute data are an average of 1 second samples for 60 seconds.

We see that the ”noise” is nice oscillations with a period of approximately 20 minutes. The oscillations are probably only found in the harbour where the tide gauge is located. WaterWater levellevel observationsobservations fromfrom BergenBergen

Red line is 1-minute observations, blue line is 10-minutes observations.

A big ship is leaving the harbour. It creates oscillations at about 10 minutes and the 10-minute values shows to low water level.

MeanMean SeaSea LevelLevel atat thethe NorwegianNorwegian CoastCoast

„ We want find a LAT surface relative to the ellipsoid inshore „ From our primary and secondary harbours we know “a lot” about LAT relative to the MSL „ We need the MSL relative to the ellipsoid, and this is our first and most difficult problem „ Our plan is to use cheap pressure gauges in the vicinity of the primary stations and “transfer” MSL to the measuring sites „ We must also measure with a GPS at each site

TidalTidal zoneszones

NARVIK KABELVÅG 0,98 0,97 0 0,96 0 Blå tall: 0 1,02 Høydekorreksjonsfaktor 0,97 1,01 0 0 relativt nærmeste primærhavn 1,00 0 0,98 0 1,02 Grønne tall: 0 0 Tidskorreksjon relativt 0,97 0 nærmeste primærhavn 1,03 10 1,01 1,04 10 1,03 5 5 1,00 1,01 5 5

BODØ TheThe modelmodel areaarea MAREANOMAREANO BackgroundBackground

„ The Barents Sea is getting more important (because of oil, gas and politics)

„ A mapping project has started where the Norwegian Hydrographic Service does the hydrographic work and other institutions examine the geology and life on the bottom.

„ The ellipsoide is used as the reference level and the GPS is used to find the water level.