WDC format

            WDC-A Digital Exchange Format 
            One-Minute Geomagnetic Data
              (Update August 1993)

1.  The logical record length is 400 coded characters containing header 
    information, blank spaces, and data for one element for one hour. Twelve
    such logical records, containing a total of 4800 coded characters, are
    combined into a single data block on magnetic media. There are 12 hours of
    data for one component for one station in each block. The data are
    sequenced according to positions 1-24 of each record. Therefore, 24 hours
    of D are followed by 24 hours of the next element for
    the same OBS, YR, MO, DA.

2.  Each observatory month is written as one file on the media. 

3.  Blocks are padded with (9's) internally to fill missing data segments
    and to complete a data set.

4.  Each logical record contains header information and data in the 
    following format: North polar distance, longitude, year, month, day, hour,
    element, observatory code, blank spaces, 60 data values,
    and an hourly mean.

1-6 7-12 13-14 15-16 17-18 19 20-21 22-24 25  26-34 35-40  389-394 395-400

5.  NPD is the observatory's North Polar Distance (0 to 180) from the 
    north geographic pole in thousandths of a degree and is allotted 6
    characters. A decimal point is implied between positions 3 an 4.

    LONG is the geographic longitude (0 to 360) measured east from
    Greenwich in thousandths of a degree and also has a 6 character field. 
    A decimal points is implied between positions 9 and 10.

    YR, MO, DA, HR are each 2-digit numbers giving the year, month, day 
        and hour (GMT).

    E is the element symbol in 1 character; it may be D, F, H, P, R, X,
    Y, or Z.

    OBS is the 2 or 3 letter abbreviation for the observatory.

    ORG is the origin of the data.
    A = Alaska Chain.
    C = Canadian Standard Network.
    D = Digitized from analog records.
    F = France
    G = U.S.G.S. Network.
    K = AFGL Chain.
    M = McClay Chain.
    R = Rostoker Chain.
    S = S.U.N.Y. Chain.
    T = Tiawan
    U = U.C.L.A. Chain.
    V = Variation Values via SMS-GOES Satellite.
    W = Walker Chain.

    BLANK are 10 character spaces reserved for future additions.

    DATA-1..DATA-60 are one-minute values of the given element for that
    data hour.

    H, Z, X, Y, or F to the nearest nanotesla and D in the tenth-minutes
    (e.g. 612 = 1 degree 1.2 minutes), each in a six character field.

    HR MEAN is the average of the proceeding 60 one-minute values.

6.  Each element value and the hourly mean is given a six-digit field 
    including a minus sign for negative values or a blank for positive values.

7.  Missing data-value spaces are padded with 99999. No alteration of 
    logical record length is required for different computer types.

8.  Data on this CD are written in monthly ASCII files as (code)YYMM
    (i.e. BOU9003 would be Boulder for March 1990).