2012 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 September 2012 to December 2012. 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 about the setup and equipment is also supplied.
non geographic dataset
: http://data.bgs.ac.uk/id/dataHolding/13607266
English
Geoscientific information
GEMET - INSPIRE themes: BGS Thesaurus of Geosciences:
Magnetic fields
Geomagnetism
Free:
NERC_DDC
creation: 2018-02
2012-09 - 2012-12
British Geological Survey
Enquiries
The Lyell Centre, Research Avenue South, EDINBURGH, EH14 4AP, United Kingdom
tel: 0115 936 3142
email: enquiries@bgs.ac.uk
Role: distributor
British Geological Survey
Enquiries
The Lyell Centre, Research Avenue South, EDINBURGH, EH14 4AP, United Kingdom
tel: 0115 936 3142
email: enquiries@bgs.ac.uk
Role: point of contact

Data Quality

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.
INSPIRE Implementing rules laying down technical arrangements for the interoperability and harmonisation of Geology
Commission Regulation (EU) No 1089/2010 of 23 November 2010 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards interoperability of spatial data sets and services

Constraints

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Available under the Open Government Licence subject to the following acknowledgement accompanying the reproduced NERC materials "Contains NERC materials ©NERC [year]"
The dataset is made freely available for access, e.g. via the Internet. Either no third party data / information is contained in the dataset or BGS has secured written permission from the owner(s) of any third party data / information contained in the dataset to make the dataset freely accessible.

Metadata about metadata

6630fdd2-67b8-1a7d-e054-002128a47908
British Geological Survey
The Lyell Centre, Research Avenue South, EDINBURGH, EH14 4AP, United Kingdom
tel: +44 131 667 1000
email: enquiries@bgs.ac.uk
Role: point of contact
2022-01-18

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