INTERMAGNET Terminology

ADJUSTED Data

Each observatory or its parent institute is allowed to modify REPORTED data files to produce ADJUSTED data, with a goal of 7 days after transmission. These adjustments may be to modify baselines, remove spikes, fill gaps etc. on any day file. When data are missing from an ADJUSTED data file, these data may be input to a GIN in a later message. This new message file can be transmitted to a GIN with the ‘A’ flag set in byte 25 of each hourly block header ( APPENDIX E3 ). ADJUSTED data are maintained online until the annual INTERMAGNET Reference Data Set (IRDS) is available. They are then archived by the GIN and only available thereafter by special arrangement.

DEFINITIVE Data

This describes observatory data which have been corrected for baseline variations and which have had spikes removed and gaps filled where possible. DEFINITIVE data have each block header byte 25 set to ‘D’ (APPENDIX E3), and the quality of the data is such that in this form they would be used for inclusion into Observatory Year Books, input to World Data Centers and included in the INTERMAGNET Reference Data Set (IRDS).

Flags

Two bytes “Flags #1” and “Flags #2” (bytes 8 and 9) of Format IMFV2.83, are reserved for IMO status information (see APPENDIX E1).

GIN

Geomagnetic Information Nodes are data centers, organized on a regional basis, which INTERMAGNET observatories send their provisional data to. GINs forward this data to the INTERMAGNET web site. GIN managers will help INTERMAGNET observatories with the technical details of establishing reliable data flow. GINs do not distribute data to users – this task is done by the INTERMAGNET web site.

IMO

An INTERMAGNET Magnetic Observatory (IMO) is a magnetic observatory equipped with magnetometers, clock, control electronics, transmitting equipment and a data collection platform (DCP), residing at the magnetic observatory site. The operation and equipment must meet INTERMAGNET standards and specifications.

IPM

INTERMAGNET Physical Media, this term collectively describes the INTERMAGNET CDs, INTERMAGNET DVDs and INTERMAGNET USBs.

IRDS

INTERMAGNET Reference Data Set contains all definitive data and metadata from the first Intermagnet publication in 1991 up to the current year, including any corrections that have been made. Published with a DOI, for example the INTERMAGNET Reference Data Set, 2015: https://doi.org/10.5880/INTERMAGNET.1991.2015.

Magnetic observatory

A permanent installation of magnetometers capable of providing magnetic field values with an absolute accuracy of better than 5 nT over a period ranging from DC to approximately 1 Sec.

NESS binary

For GOES users, each 16-bit binary word is encoded as 3 pseudo ASCII bytes, so that the 126 bytes of IMFV2.83 data are encoded as 189 bytes NESS binary (see APPENDIX E2).

Offset

The component offset values determined by the INTERMAGNET coding algorithm that has been applied to recorded data for coding data stored in the “minute value” section of Format IMFV2.83 (see APPENDIX E1).

QUASI-DEFINITIVE Data

As the name implies, the data should be close to the expected definitive value, but is to be delivered more rapidly than an observatory’s annual definitive data. This initiative will be useful for a number of scientific activities, where timely and close-to-definitive data is essential. For example, quasi-definitive data will be particularly useful in joint analyses of geomagnetic and other phenomena, together with data measured by satellites. Quasi-definitive data are 1-minute or 1-second data (observatories are encouraged to produce both minute and second data) that can be submitted to INTERMAGNET as (H, D, Z) or (X, Y, Z) and have the following properties:

  1. Corrected using temporary baselines

  2. Made available less than 3 months after their acquisition

  3. Such that the difference between the quasi-definitive and definitive (X, Y, Z) monthly means are less than 5 nT in any component for every month of the year

Point C is checked a posteriori by comparing quasi-definitive and definitive data from the previous year. Observatories are strongly encouraged to submit quasi-definitive data that is thoroughly controlled, i.e. de-spiked, free from corrupted data, data gaps filled in from back-up systems, and with the best possible baseline at the time of submission. Submission of quasi-definitive data should not be seen as having satisfied the requirements for definitive data. The annual definitive data, again thoroughly controlled and with a baseline based on a full year of absolute measurements, shall be submitted in the formats for definitive data at latest by the deadline agreed by INTERMAGNET.

Reference Measurement (RM)

Values provided automatically by an IMO using 2 independent instruments for inter-comparison. Reference Measurements are provided by the institute operating the observatory site using satellite communications to INTERMAGNET GINs using the Format IMFV2.83. The RMs are applied to reported data to produce adjusted data and to supplement baseline control.

REPORTED Data

Data as output by an observatory, transmitting through a satellite or using email. REPORTED data have not had any baseline corrections applied, may contain spikes and may have missing values. When ADJUSTED data are available, REPORTED data are removed from online access.

Time stamp

The time of the first sample of the data block:

  • Greenwich day 1 through 366 encoded as a 12-bit binary number.

  • Minute of the Greenwich day : 0 through 1439 encoded as a 12-bit binary number (see APPENDIX E1 and APPENDIX E2).