Abstract
The reliability of the Historical Italian Geomagnetic Data Catalogue, comprising 536 directions and 393 inten- sities, has been assessed by comparing the historical geomagnetic measurements with the GUFM1 model pre- dictions. Such measurements were assessed at three selected relocation centres. For all the data contained in the Catalogue it has been calculated the discrepancy between the relocated data and the GUFM1-model prediction at the relocation centres. There is a correlation between relocation distance and the mean discrepancy. The up- per limit of discrepancy assumable as relocation error has been selected using error distributions previously cal- culated using geomagnetic field models. Angular and intensity threshold lines have been slightly shifted upwards to account for the estimated error of GUFM1 model itself at the considered region, mainly due to the crustal field. The Italian database proved to contain reliable data, as only a very low percentage of data (namely 14 di- rections and 20 intensities) can be considered anomalous. Possible explanations for such questionable data are suggested. All the remaining data of this catalogue could thus be added to the databases used to produce region- al or global geomagnetic models.
Highlights
The geomagnetic field is commonly described through its potential, which can be represented by a spherical harmonic series
As is stated in Casas and Incoronato (2007) the distribution of relocation errors can be used by archaeomagnetists as an indication of the maximum error induced by such a practice
The calculation of the relocation error for any given geomagnetic datum requires the knowledge of the «true» value of the magnitude considered at the relocation centre
Summary
The geomagnetic field is commonly described through its potential, which can be represented by a spherical harmonic series. Relocation is routinely carried out by archaeomagnetists and consists on reducing data to a central location This procedure permits to compare geomagnetic data from different loca-. As is stated in Casas and Incoronato (2007) the distribution of relocation errors can be used by archaeomagnetists as an indication of the maximum error induced by such a practice. This conclusion is restricted to periods with similar or lower values of the ratio between dipole to non-dipole contributions than in the present geomagnetic field; this could cover at least the last 7000 years (Korte and Constable, 2005)
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