Abstract
Scalar magnetic field data have been collected from the world's ocean areas by marine research institutes on a routine basis since the early 1950's. About 13 million such data points reside in the collection of the National Geophysical Data Center in Boulder Colorado. These data comprise a valuable source of measurements for modeling the geomagnetic field of the Earth. To derive a suitable reduced data set for such modeling, each ship track is divided into 220km segments. Within each segment the data are tested for magnetic disturbance and for large deviations from the International Geomagnetic Reference Field. The mean of the acceptable data is computed for each segment, together with the standard error of the mean. This results in 24, 243 reduced points. The distribution of the reduced data in time, position and local time is presented and discussed.
