How to Use the Se havnivå Online Service

To get information about an area, you can search for place or position.

Place: Enter the name of a place and select the location from the drop-down menu that appears. Be aware that many places have the same name but are located in different municipalities or counties.

Position: Enter the latitude and longitude in decimal degrees, positive values indicating east/north.

Search hits and tab content

After your search is complete, you will be redirected to the "Tides and water level" tab. This shows water level and tidal information, vertical datums and historical data for the location in question.

Then, you can move back and forth between the "Tides and water level" and "Sea level" tabs for the location in question.

The Tides and water level tab

You will find information concerning the data of your search directly below this tab.

Example: Data from the permanent tide gauge in Bergen is used to calculate tidal conditions at Stord. The time lag between the two locations is 10 minutes. The tidal differences at Stord are smaller compared to Bergen, so the height is multiplied by a factor of 0.76.

The coast is divided into approximately 600 zones that have roughly the same tidal conditions, based on water level measurements from the permanent stations and many short measurement series from other locations. The tide in each zone is related to the nearest permanent tide gauge using a time lag and a conversion factor for the height.

The Norwegian Mapping Authority’s Hydrographic Service operates a network of 24 permanent tide gauges distributed along the Norwegian coast, and one in Ny-Ålesund on Svalbard.

Based on the tidal zones, we can offer estimated water level data for any location along the Norwegian coast (with a few exceptions).

Operational message

If the place you are searching for is located too far from the coast, or is an area without sufficient information (data), an operational message about this will appear at the top of the search hit. For example, there is not sufficient data in the area between Lista and Tananger.

Current water level

The first tidal information you get from your search is the current water level (last measured), above Chart Datum. Next follows the approximate time for the next expected low and high tide. Note that these two do not include the weather effect, and may therefore vary from the water level forecast you will find in the graph below.

Water level - the graph

You can:

• Choose which curves you want to view/hide by tapping them
• Choose reference level (chart datum, mean sea level or the national vertical reference system (NN2000))
• Choose the period of time, both past and future
• Zoom
• "Mouse over" to show the time and height of the curve

Predicted tide – red curve:

After measuring the water level in one particular place (for at least a few months, but preferably over several years), it is possible to analyze the data in order to determine the tidal ‘characteristics’. In turn, this can be used to determine the tide at the location at any given time, and also provides the basis for tide tables. Predicted tides are also called astronomical tides because they result from gravitational effects from the sun and moon. Atmospheric effects (weather) on the water level are not included.

Water level – blue curve:

This is the water level that has actually been observed. The water level at a certain place is the sum of the astronomical tide and the weather’s effect on the water level, and is continuously measured by our permanent tide gauges.

Water level forecast – green curve:

With the help of models, the Norwegian Meteorological Institute predicts the effect the weather has on the water level five days ahead. The predictions are continuously adjusted using observations from the Norwegian Mapping Authority. These forecasts are added to the Norwegian Mapping Authority’s predicted tides, and we can provide a water level forecast five days in advance.

Table

The content of the graph can also be viewed in a table, and you can choose the interval between each value (one hour or 10 minutes).

The table also shows the weather effect. This is the difference between observed water level and predicted tide. In particular, air pressure variations and wind cause water levels to vary. Only past readings of this difference are given.

Vertical datums

The "Vertical datums" shows a figure with the most important vertical datums for the chosen location, including high and low tides with various repeat intervals (return periods). Zone information is used to calculate the levels. You can choose different reference levels in the figure (chart datum, mean sea level or the national vertical reference system (NN2000)).

It is possible to turn different groups on or off.

The figure can be downloaded as a pdf, where explanations of the different levels are given on page 2.

Tide tables

The tide table lists heights and associated times for all high and low waters for your search location. You can choose reference level and the period of time, both past and future.

Historical data

Here you will find annual values of the highest, lowest and annual mean water levels for the chosen location during a selected period. You can choose different reference levels in the figure. The data can also be viewed in a table, given month by month for the selected period.

Note that the statistics are based on data from the permanent tide gauges. This means that if you choose a place such as Stord, there will be no statistics shown. In these cases you will get information about the nearest permanent tide gauge, and be able to be redirected to that location.

The Sea level tab

The projections presented here are based on the report "Sea Level Change for Norway- Past and Present Observations and Projections to 2100", commissioned by the Norwegian Environment Agency. All numbers are corrected for post-glacial rebound.

Projections of future sea levels

This shows projections of future sea levels for different greenhouse gas emission scenarios up to the year 2100. This applies to the municipality in question.

Here, you will also find recommended figures from the Norwegian Directorate for Civil Protection (DSB) that can be used for planning purposes.

Land uplift

After the ice from the last glacial period melted, we have seen a gradual and ongoing upward movement of the land. The table shows annual (local) land uplift for the chosen location. The values are based on the Norwegian Mapping Authority’s Glacial Isostatic Adjustment model (GIA).

The table also shows the predicted local land uplift for the years 2030 and 2100, relative to the year 2000.