<p><strong>Abstract:</strong></p><p>The second part of the history of the Algerian magnetic repeat station network goes back to 1989 when the new one was started with 37 stations. It was then followed by three other networks in 1993, 1997 and 2005. The first part of this history started at the beginning of the XX<sup>th</sup> and ended ca 1956.</p><p>After a 14-year break, we launched a new repeat stations network in February 2019. The number of carried out stations was increased to 51 to try to cover all the territory.</p><p>Each repeat station network consists of stations of periodically, say &#160;5-6 years, measured of three components of the Earth's magnetic field. to try to derive the spatial distribution of the geomagnetic field of Algeria and it's secular variation. This periodicity is also very important for the need to update local as well as global geomagnetic field models such as the International Geomagnetic Reference Field (IGRF).</p><p>In this work we describe the new 2019 Algerian repeat station network. Then we will discuss the steps of the absolute measurements using two methods. The first one is called the &#8216;method of zero&#8217; and the second one &#8216;method of residuals&#8217;. The accuracy and resolution of the instruments and data reduction used and their effect on the final results will as well be discussed. We derive the spatial distribution of the geomagnetic field, and its secular variation. Finally, we will show how local, for instance regional polynomial modeling, is the key issue.</p><p><strong>Key words</strong>: geomagnetic repeat network, absolute measurements, zero method, residual method, magnetic maps of Algeria, secular variation.</p>
The Italian magnetic repeat station network: results from the 2012.5 ‘Reduced Network’ completion
