Comparing the Accuracy of BMKG Geomagnetic Maps with those of IGRF over the Indonesian Region

摘要

In compliance with the resolutions of IAGA (International Association of Geomagnetism and Aeronomy), every five years, BMKG or Meteorology, Climatology and Geophysics Agency of Indonesia builds geomagnetic field maps based on actual measurements in about fifty ground stations. Using data collected from satellites and from observatories around the world, IAGA also builds a global model of geomagnetic field termed IGRF (International Geomagnetic Reference Field). In this study, we compare the accuracy of BMKG maps with that of IGRF to evaluate the continuation of BMKG geomagnetic mapping program. The comparison, based on 1985-2010 data, was conducted by spatial analyses using collocated cokriging and kridging with external drift to map the observation data. The results show that BMKG maps differ from IGRF maps. For example, BMKG total intensity maps show changes of anomaly of -300 nT in 1985-1990 to -20 nT in 1995-2000 and to 200 nT in 2005-2010. The inaccuracy of IGRF maps over Indonesia are due to the scarcity of geomagnetic stations used by IGRF in the region and to the complexity of Indonesian geology. In conclusion, the existing BMKG geomagnetic mapping program is satisfactory. However, the quality of declination maps might be improved by adding several new ground stations.