BCMT

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:

 

Code Nom WGS84 2015.5
Latitude Longitude Altitude H (nT) D (°) Z (nT) F (nT)
BIQ Biarritz-Bayonne-Anglet 43.46848 358.48116 74.6 23839.525 -0.503 39397.267 46049.682
BVE Brive-Vallée de la Dordogne 45.03841 1.4896 310 22897.846 0.228 40734.249 46729.504
CEQ Cannes-Mandelieu 43.55002 6.95132 4.3 23760.463 1.481 40119.971 46628.834
CFR Caen-Carpiquet 49.17612 359.55569 78 20693.521 -0.698 43293.902 47985.079
EDM La Roche sur Yon- Les Ajoncs 46.69979 358.61651 90.5 22045.514 -0.721 41708.396 47176.671
ENC Nancy-Essay 48.68663 6.22691 229 20690.161 1.454 43424.981 48102.027
FSC Figari-Sud Corse 41.49718 9.08992 26.5 24947.330 2.308 38939.084 46245.715
LYN Lyon-Bron 45.725 4.94483 201 22462.497 1.151 41414.208 47113.899
MXN Morlaix-Plougean 48.60846 356.19068 84.4 21010.346 -1.790 42935.654 47800.625
PGF Perpignan-Rivesaltes 42.7428 2.87124 44 24154.660 0.762 39155.421 46007.976
XVS Valenciennes-Denain 50.32431 3.46435 50.3 20010.735 0.560 44191.257 48510.479

 

Download 2012 to 2015 results in Excel format here.

Download 2012 to 2015 results in MagnetE format here.

In order to calculate the declination at any coordinates in metropolitan France, download this software.

Documents:

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