Data Formats
The INTERMAGNET Operations Committee defines and publishes
data formats for use by INTERMAGNET participants. The data
produced by INTERMAGNET will use one of these formats:
Due to the method that
is used to record geomagnetic data it is not possible to make
continuous measurements of the absolute value of the Earth's
magnetic field. Instead a continuous record of variations in the
field is made automatically, usually using computer controlled
instrumentation. These data are made available as a preliminary
data set, called reported data. The first operation that
occurs on the data is the removal of any contamination (such as
might be caused by instrumentation faults or man-made
interference). The resulting data set is called adjusted data.
This is then combined with a baseline that has been calculated
from regular spot-values of the absolute field, which are made
periodically using manual observation techniques. The combined
data set, called definitive data, is a record of the
absolute value of the field, but it is not made available until
some time after the event (typically a few months after the end
of each year).
In order to satisfy the requirements for both faster and more accurate
data, INTERMAGNET has created two separate services for data dissemination.
The INTERMAGNET CD-ROM is published annually
and contains definitive data from all participating observatories. The
Geomagnetic Information Nodes (GINs) provide
an on-line repository for reported and adjusted data. Data are sent from
the participating observatories to the GIN within 72
hours of recording. They are then held on-line until the annual CD-ROM
is available.
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