French Repeat Station Survey
What is it?
Geomagnetic repeat stations are defined locations within a certain region (usually a country) where absolute measurements are carried out in regular time intervals, usually annually to once every 5 years. Repeat station data are used to map the main field and study secular variation in detail. The French National Observatory (CLF) is responsible for the French repeat station measurements.
How is it made?
Until 2012, the French geomagnetic repeat station network consisted of 32 points out of a denser network from former ground vector surveys. Regular repeat station surveys started in 1948 and were carried out every 5 years. The measurements are taken by a fluxgate theodolite (D, I) and a proton magnetometer (F).
The relevance of traditional magnetic repeat station networks to geomagnetic modeling has been increasingly challenged during the last decade, as the Ørsted and CHAMP satellites provided data of unprecedented precision and spatial resolution. Yet magnetic repeat networks organized on a national or regional basis can still be viewed as relatively inexpensive safety nets in case satellite data are not available. A new method for magnetic repeat measurements has been developped, where repeat stations are located on airports, azimuth sightings are determined using GNSS geodetic receivers and magnetic measurements are performed at night (around 0200 local time). It is believed this method improves the measurement precision while keeping the cost low, by facilitating the measurement execution. It was first implemented in metropolitan France during the summer 2012. A full description can be found in this publication: A new measurement Method for Magnetic Repeat Station. Here is the 2015 map:
Results of latest observations:
|Latitude||Longitude||Altitude||H (nT)||D (°)||Z (nT)||F (nT)|
|BVE||Brive-Vallée de la Dordogne||45.03841||1.4896||310||22897.846||0.228||40734.249||46729.504|
|EDM||La Roche sur Yon- Les Ajoncs||46.69979||358.61651||90.5||22045.514||-0.721||41708.396||47176.671|
Download 2012 to 2015 results in Excel format here.
In order to calculate the declination at any coordinates in metropolitan France, download this software.
IAGA Guide for Magnetic Repeat Station Surveys
Le réseau des stations de répétition magnétique de la France 2012-2013
Le réseau des stations de répétition magnétique de la France 1982
Le réseau des stations de répétition magnétique de la France 1977
Le réseau des stations de répétition magnétique de la France 1972
Le réseau des stations de répétition magnétique de la France 1967