IAGA 2002 Data Exchange Format

• Additions made June 2015
• Additions made August 2011
• Additions made July 2003
• Revision December 2001

This page provides information on the International Association of Geomagnetism and Aeronomy (IAGA) ASCII Exchange Format, which was adopted August 2001. Content includes some general information and a description of the file header, comment records, data header and records, file naming recommendations, and sample data file.

This format is intended as a data exchange format for geomagnetic data (samples and means) from observatories and variometer stations at time intervals from millisecond up to and including monthly means. The format is comprised of:

• Twelve (12) mandatory and one (1) optional file header records
• Unlimited optional comment records
• One (1) mandatory data header record
• A series of data records
• Every record is 70 characters long plus the machine-dependent carriage return / line feed

Pad records with spaces if needed. Data records report exactly four magnetic field elements (DHIF, DHZF, XYZF, or DHIG, DHZG, XYZG). Use missing data values (8s or 9s) if fewer than four elements are available.

The 12 Mandatory and 1 Optional File Header Records

Mandatory header and optional comment records begin with a space character in column 1 and end with the vertical bar | (ASCII 124) in column 70. Content labels begin in column 2, and descriptions begin in column 25.

• This format is designated IAGA-2002.
• Source of Data is the institute responsible for collecting the data.
• Please spell the entire station name; do not use abbreviations. Capitalize the first letter.
• The IAGA Code is the official IAGA 3-letter station code. It should be in capital letters and correspond to the IAGA list of magnetic observatories. Variation stations must check observer suggested 3-letter codes against the IAGA list (WDC SEG, Boulder) and confirm through the IAGA Division V WG1 or leave the code blank.
• Location of the station is reported to the one thousandth degree in geodetic latitude (positive north) from -90 to 90 degrees and in geodetic longitude (positive east) from -180 to 180 or 0 to 360 degrees.
• Report elevation in meters above mean sea level.
• "Reported" refers to the magnetic field elements contained in the data record, in the order recorded in the data record. Valid values are DHIF, DHZF, and XYZF (or DHIG, DHZG, and XYZG). Use E/V instead of D/I for declination/inclination given in intensity units (ONLY if data type is variation). G is defined by G=F(v)-F(s), where F(v) represents the total field value calculated from the main observatory instrument ("vector F") and F(s) represents the total field from an independent (scalar) instrument ("scalar F").
• Sensor Orientation is the physical orientation of the observing instruments, i.e. XYZF, HDZ.
• Digital Sampling is the rate (in seconds) of the data sampling of the magnetic field sensor (instrument) or the digitizing interval for analogue data.
• Data interval type is the mean or instantaneous time interval of the data. Common values include 1-minute (00:30-01:29), 1-minute (00:00-00:59), 1-hour (00-59), 1-day (00-23) and 1-month (01-31); the last day could also be 30, 29, or 28. There are many possible intervals, including a fraction of a second (instant value), averages by 1-second (501-1500), 1- second (0-1000), 10 second, or 2.5 minute. Define the type of mean and how values are centered in the comment section.
• Data type is provisional (P), definitive(D), quasi-definitive (Q), or variation (V).
• Publication date (optional) is the date when the data is published. This was added in June 2015. The inclusion of this line (#13) is optional but desirable for modern data. The old data files can not be modified. Example is " Publication date 2014-10-20".

Optional Comment Header Records

Use these records to record important information concerning the data that are not contained in the defined fields. Types of information may include the type of means and how the mean values are centered, important gaps in the data record, or explanations of missing values (9 filled element field).

• Every record begins with a space character in column 1 and # (hash or number sign) in column 2.
• The end of each record is indicated with a vertical bar | (ASCII 124) in column 70.
• Include the formula for computing the missing (non-reported) magnetic elements. For example, if an observatory reports XYZF, the comments should contain the formula for computing HDI.
• Addition July 2003: for transmission of incomplete day files, include two additional optional comment headers stating the start time and duration in seconds.

These records must have the form:

#Start Time hh:mm:ss

duration-in-seconds

• Addition July 2003: for computing approximate values of D in angular units from E values in nT, one additional optional comment header is required. This record should contain an approximate H value (e.g., the most recent annual mean value or a value from the IGRF), and must be in the form:

#Approx H 17000

Mandatory Data Header Record

The mandatory data-header record contains column headers useful for multi-station analysis. Elements, both type and order, are indicated in the file-header field Reported.

• The date and time headers are DATE, TIME, and DOY (day of year)
• The magnetic element headers comprise four letters: three letters for the observatory IAGA code and one letter for the magnetic element reported. Valid values are H, D (or E), I (or V), X, Y, Z, F (or G). The column headers are space delimited
• The end of each record is indicated with a vertical bar | (ASCII 124) in column 70

The Data Records

The data records contain the date, time, and magnetic field elements reported. Report data to the least significant digit. Indicate missing data with 99999 to the corresponding accuracy for a given component (e.g., 99999.0 or 99999.00). If an element is not observed, please record 88888 (to the corresponding accuracy) in that field. The format for field elements is 4(1X, F9.2). Each record is exactly 70 characters long plus the machine dependent carriage return / line feed.

• DATE is the calendar date in ISO YYYY-MM-DD format (4-digit year, month as 01-12, day as 01-31).
• TIME is in ISO hh:mm:ss.sss format (hour as 0-24, minute as 0-59, second as 0-59 Note: if the hour is 24, the minute and second must be 0).

Values beyond the time interval of the means being reported must be zero-filled i.e. 14:01:00.000 for 1 minute data for the 14th hour, first minute. DOY is the day of the year, from 1 - 365 (or 366 for leap years). Describe the method of average, i.e., centered to the hour for hourly means, in the comments area.

• D and I are reported in angular units of minutes of arc to the precision of the instruments.
• F, H, X, Y, Z, E, G, and V are reported in nanotesla and a fraction of nT.
• Return to top.

Recommended File Name Procedure

To improve the ease with which data are exchanged and recognized, IAGA recommends the following guidelines and style for naming files containing magnetic observatory data. The recommendations closely follow the current International Standards Organization (ISO) Level II recommendations, and are fully compliant with both the Joliette extension to Level II and to the proposed modifications for the ISO standard. These recommendations are for data exchange and do not necessarily apply to data archive. Some changes were made in this section in July 2003 to allow for the existence of multiple fragments of data starting at different times (which is a possibility for some data transmission systems) and to ease usage with compression programs.

1. File names are composed of two parts, the base name and a three-character extension. A full stop (period) separates the base from the extension. The base name may be up to 27 characters long. The extension is exactly three characters (total file name length not to exceed 31 characters). This format is sometimes referred to as the "27.3" format.

BASENAME (1 to 27 characters) "." EXTENSION (3 characters)

Ex. my_file_name.dat

2. File names are composed of lower case a-z, 0-9, underscore "_", and dash "-" characters. No spaces, unusual characters (i.e. *, /, \, :, ;, ?) or upper case characters allowed.
3. File names must begin with the IAGA 3-Letter Code, Date, and Type of data. The Extension defines the Data Interval (monthly, daily, hourly, minute, or second data). The Extension is duplicated in the last three characters of the base name, so that if the Extension is stripped on compression the Data Interval is not lost. The file name only indicates the general data interval, specific information is contained in the file header Data Interval field (i.e. 2.5 and 1-minute averages are both "minute" data, 10 second averages and 1 second instantaneous are both "second" data).
4. The first several characters in the base name are strictly defined. Files may be further defined with the remaining characters by using an underscore "_" to separate the standard name. For example, naq20020101dmin.min and naq20020101d_2-5min.min are both acceptable names for 2.5 minute definitive data from Narsarsuaq.

General format: iagyyyymmddtint.int

Where:

• iag = IAGA 3-letter observatory code
• yyyy = four digit year (i.e. 2002)
• mm = two digit month (i.e. 01 for January, 12 for December)
• dd = two digit day of month (01-31)
• t = type of data (p - provisional, d - definitive, q - quasi-definitive v - variation)
• int = data interval (mon - monthly, day - daily, hor - hourly, min - minute, sec - second)

Where:

• iag = IAGA 3-letter observatory code
• yyyy=four digit year (i.e. 2002)
• mm=two digit month (i.e. 01 for January, 12 for December)
• dd=two digit day of month (01-31)
• hh=hour at which data starts (00-23)
• MM = minute at which data starts (00-59)
• ss = second at which data starts (00-59)
• t = type of data (p - provisional, d - definitive, q - quasi-definitive v - variation)
• int = data interval (mon - monthly, day - daily, hor - hourly, min - minute, sec - second)