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AGNES determines your position and the weather

The permanent measuring network, AGNES, can be used to determine positions with centimetre-level accuracy. But few people knew until now that AGNES is also used to produce weather forecasts.

01.02.2021 | DKW

Weather satellite
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AGNES, Switzerland's Automated GNSS (Global Navigation Satellite System) Network, consists of navigation satellite receiving stations at 30 different locations. These stations record all available signals to the currently operational GNSS navigation systems: GPS (USA), Glonass (Russia), Galileo (EU) and BeiDou (China).

The AGNES network has become the central infrastructure for surveying in Switzerland. The high degree of absolute accuracies also enabled the introduction of the new coordinates reference system LV95 on which all geodata in Switzerland has been based for the last three years. Each and every one of us can determine our location with a smartphone even without the AGNES network, but only to an accuracy of a few metres.

AGNES and the water vapour content in the atmosphere

Let's talk about the lesser-known function of AGNES: thanks to the AGNES network and its data analysis, it is also possible to obtain information on water vapour content in the atmosphere. This is possible because the signals are slowed down by water vapour on their way from the receiver to the satellite in the lower five kilometres of the atmosphere. In this way, one can indirectly deduce the water vapour content from the propagation delay and obtain information on the weather pattern from this.  

Principle of GNSS meteorology
Principle of GNSS meteorology

Cooperation across borders

In addition to the measuring network, swisstopo also operates a permanent Networks Analysis Center (PNAC) which evaluates the data from Switzerland and about 160 European stations. This analysis takes place every hour and delivers the results with a time delay of about 30 minutes. The results are made available to the Federal Office of Meteorology and Climatology MeteoSwiss as well as to other European meteorological institutions.

This cooperation between two federal offices can also be observed in other European countries. The data exchange of GNSS results for the benefit of weather forecasts has developed considerably over the last 20 years. Currently, 15 data centres process the data from a total of 3,500 GNSS stations. Users include meteorological organisations which use the results for their weather forecasts. In some countries, this data is already integrated directly into the numerical weather models. MeteoSwiss uses the results from the AGNES analyses to make comparisons with its own weather forecasts.
The results are also compared in Payerne, for example, where a weather balloon with meteorological instruments is launched twice a day. However, MeteoSwiss and swisstopo also jointly operate measuring stations at other locations.

 
 

GNSS stations in swisstopo's evaluations
GNSS stations in swisstopo's evaluations

Weather forecasts and climate change

For some years now, research has been conducted into a further field of application for AGNES: the development of climate change. AGNES can be used not only for short-term weather forecasts, but also to describe climate change. From the time series of station coordinates, which now span more than 20 years, statements can be made about the tectonic movements of the surface of Switzerland. In this way, attempts are also being made to draw conclusions about climate change from the changes in water vapour content in the atmosphere.

Who knows what swisstopo will contribute to in the future thanks to the AGNES data?

Federal Office of Topography swisstopo Seftigenstrasse 264
P.O. Box
3084 Wabern
Tel.
+41 58 469 01 11

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Federal Office of Topography swisstopo

Seftigenstrasse 264
P.O. Box
3084 Wabern

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