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Format Descriptions for Hourly Values and One-minute Values
of Geomagnetic Field Components

Russian version



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Hourly Values Format
Columns  Format        Description
  1-3      A3   Observatory 3-letter code
  4-5      I2   Year (last 2 digits, 82=1982)
  6-7      I2   Month (01-12)
    8      A1   Element (D, H, X, Y, Z, or F)
  9-10     I2   Day of month (01-31)
 11-12     A2   Blanks 
 13-14     A2   Arbitrary
    15     A1   International quiet or disturbed days, Q=1, D=2
    16     I1   Blank for data since 1900, 8 for data before
 17-20     I4   Tabular base, in degrees for D and I, hundreds of 
                nanoTeslas (gammas) for the intensity elements.
                The bases are right adjusted and signed if negative. 
                Negative values are identified with a minus sign 
                either adjacent to the first significant digit or 
                in the high-order position of the field (position 17).  

                NOTE: A blank digit will not appear between a (-) 
                sign and the first significant digit. For example, 
                a base may appear as -050 or b-50 but not as -b50 

 21-116  24I4   Twenty-four 4-digit Hourly Values for the day.
                The values are in tenth-minutes for D and nanoTeslas 
                (gammas) for the intensity elements. 
                The first hourly value represents the mean value 
                between 00:00 UT and 01:00 UT, ..., the 24th value 
                represents the mean between 23:00 UT and 24:00 UT. 
                Rules for negative values are the same as those 
                described for tabular bases. 
                A missing value is identified by 9999.

117-120    I4   Daily mean. Rules for negative values are the same 
                as those described for tabular bases. If any of the 
                hourly mean values for the day are missing 9999 will 
                appear as the daily mean.

The 25 values in positions 21-120 will have the range -999 to 9998, 
with 9999 reserved for missing values. To avoid a 4-digit negative 
value in positions 21-116, the tabular base will be adjusted for that 
day; for example for D, one degree is subtracted from the base and 600 
units are added to each of the hourly values for the day; for the 
intensity elements, 500 nT are subtracted from the base and 500 nT 
are added to each of the hourly values for the day.
One-minute Values Format
The logical record length is 400 coded characters containing header
information, blank spaces, and data for one element for one hour. 

Each logical record contains header information and data in the 
following format: 

Columns  Format        Description
  1-6       I6    Geographic Co-Latitude in 0.001 degree
  7-12      I6    East Geographic Longitude in 0.001 degree
 13-14      I2    Year (last 2 digits, 82=1982)
 15-16      I2    Month (01-12)
 17-18      I2    Day   (01-31)
    19      A1    Component of the field (H,E,Z)
 20-21      I2    Hour  (00-23) 
 22-24      A3    Observatory's IAGA 3-letter code
    25      A1    Origin of data (D - digital, A - digitized)
 26-34     9A1    Blanks
 35-40      I6    1-st 1 minute average
 41-46      I6    2-nd 1 minute average
   ...      ...       .....
388-394     I6    60-th 1 minute average 
395-400     I6    Hourly mean value

DATA-1 ... DATA-60 are 1-minute values of the given element for that
hour. H, X, Y, Z, or F are given to the nearest nanoTesla (gamma). D is
given to the nearest tenth-minute of arc (612 = l degree + 01.2 minutes
East). Each value is in a 6-character field.

Missing data spaces are padded with 99999. No alteration of logical
record length is required for different types of computers.

Codes for sources of digital magnetometer data in the WDC system not
only indicate the source organization, but also show whether the data 
are average values or point data. For example, 1-minute point values 
scaled from analog magnetograms for the production of AE indices are 
coded with a "D" because they are "digitized".  Typically, digital 
1-minute values received by WDCs from organizations operating automatic
magnetic observatory instruments are averages of more frequendy sampled
values, e.g. 10-second point samples. Different organizations process
their higher time resolution observations in different ways. Some may
filter and smooth the observations. Some follow the practice recom-
mended by IAGA of averaging higher time resolution samples from
before and after the minute to obtain a 1-minute value centered 
exactly on the minute. Others average values from the beginning of a 
given minute to the beginning of the next minute, effectively centering
the mean on the half-minute, in similar fashion to the processing of 
1-minute values to obtain hourly means. If the method used to obtain 
1-minute average values is important to a user, the WDC will assist in 
determining the exact procedure applied.

In general, digital values from national networks are "absolute" and 
are tied to baselines determined by are operating institutions. Often 
only timely variations data are needed to support special research 
campaigns and digital values may be transmitted from regular 
observatory sites via satellite relay platforms. Such values are 
"flagged" with a "V" as noted below and eventually are replaced by the
standard digital observatory output. Values from special networks such 
as the IMS chains are variations only.  Attempts are made to check the 
absolute output of these instruments but usually no systematic absolute
observations are possible or they are later replaced by adopted 
standard observatory digital values.

ORG    (data origin codes)

A =    Alaskan meridian magnetometer chain (includes Canadian sites) for
C =    Canadian standard observatory network
O =    point samples digitized from analog magnetograms
F =    France
G =    USGS standard observatory network (one station operated by NOAA)
J =    Japan
K =    US AFGL E-W sub-auroral zone magnetometer chain
R =    Western Canadian meridian magnetometer chain operated for IMS
T =    Lungping magnetic observatory, Taiwan.
U =    E-W mid-latitude magnetometer chain operated for IMS 
V =    Variations only sent via NOAA GOES satellite relay
W =    Eastern Canadian meridian magnetometer chain operated for IMS

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