2018 High frequency magnetic field induction coil data from Eskdalemuir Observatory, UK
High frequency (100 Hz) data from two horizontal induction coils measuring the Earth's magnetic field at the Eskdalemuir Observatory in the United Kingdom. The data covers the period from January 2018 to December 2018. Also included are examples of Matlab code and the frequency calibration files to convert to the raw data to SI units. Thumbnail spectrograms and metadata are also supplied.
nonGeographicDataset
https://www.bgs.ac.uk/services/ngdc/accessions/index.html#item131925
name: Data
function: download
https://www.bgs.ac.uk/services/ngdc/citedData/catalogue/dfd39af7-f67b-4ed0-8c55-3d87780b295b.html
function: information
http://data.bgs.ac.uk/id/dataHolding/13607571
eng
geoscientificInformation
publication
2008-06-01
Magnetic fields
Ionosphere
revision
2011
NERC_DDC
2018-01
2018-12
creation
2020-01-14
notPlanned
There are two induction coils located in the Eskdalemuir Observatory. • They oriented in the following directions: North-South (CH1) and East-West (CH2). • The data are sampled at 100 Hz. • The raw ASCII data are given in 24 one-hour files starting at the 00:00:00.00 UT for each day. • Each hour file contains 60 * 60 * 100 Hz = 360000 ASCII values. • The last value of the day is for the time 23:59.59.99 UT. The hourly files for each year have been tarred together and then gzipped up into a single file for year e.g. ESKINDCOIL_2015.tar.gz Within the annual files the names of each data file for each hour are given as CH{1,2}_{year}_{month}_{day}_{hour}.dat e.g. CH1_2015_01_01_22.dat This is the data for Channel 1 (CH1) for the 1st January 2015, hour 22 (22:00:00.00 – 22:59:59.99 UT) Each hourly file, when unzipped, has a size of 3.6 Mb. Calibration information on the data and the manufacturer and model of the magnetic sensors: The coils are French-built from around the 1970s (CM11E1) which came from the NERC Geophysical pool to BGS in 2003. They are connected to 24-bit Guralp digitizer previously used for seismology applications. The data are converted from an analogue voltage by the digitizer, sent to a computer located in a vault around 150m away, recorded onto the disk and retrieved once per hour back to the Edinburgh office The raw data in the files are given in digitizer units (with an arbitrary offset of ~-570,000) which can be converted back to Volts. The induction coils output an analogue signal which is calibrated by Volts per nT in the frequency domain (not the time domain). However, the time-series can be approximately converted to SI units of Tesla (see below) • The frequency dependence of the coils is around 50.1 mV per nT between 0.1 – 100 Hz. • The digitizer has a conversion factor of 3.491*10^-6 Volts per count for Channel 1 and 3.475*10^-6 Volts per count for Channel 2. Thus, the easiest way to convert to (approximate SI units) in the time domain is to Butterworth filter the time series data between 0.1 and 50Hz frequencies, to get a filtered digitizer signal. Multiply the filtered signal by the Volts per count ratio of the digitizer (e.g. 3.491*10^-6 for Channel 1) to get the value in Volts. Then multiply the time series by 1/50100 nT/Volt to get the values in nT. There is some example Matlab code (ProcessInductionCoilData.m and the exact frequency response in CoilCalibration_CM11E1.m) available.
publication
2011
false
See the referenced specification
publication
2010-12-08
false
See http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2010:323:0011:0102:EN:PDF
ASCII text file
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British Geological Survey
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EDINBURGH
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United Kingdom
0115 936 3142
0115 936 3276
distributor
British Geological Survey
The Lyell Centre, Research Avenue South
EDINBURGH
EH14 4AP
United Kingdom
0115 936 3142
0115 936 3276
pointOfContact
British Geological Survey
The Lyell Centre, Research Avenue South
EDINBURGH
EH14 4AP
United Kingdom
+44 131 667 1000
pointOfContact
2024-03-14