Beggan Ciaran D, Eaton Eliot, Maume Eleanor, Clarke Ellen, Williamson John, Humphries Thomas
British Geological Survey Edinburgh UK.
Geosci Data J. 2023 Jan;10(1):73-86. doi: 10.1002/gdj3.151. Epub 2022 Mar 28.
Continuous geomagnetic records of the strength and direction of the Earth's field at the surface extend back to the 1840s. Over the past two centuries, eight observatories have existed in the United Kingdom, which measured the daily field variations using light-sensitive photographic paper to produce analogue magnetograms. Around 350,000 magnetograms have been digitally photographed at high resolution. However, converting the traces to digital values is difficult and time consuming as the magnetograms can have over-lapping lines, low quality recordings and obscure metadata for conversion to SI units. We discuss our approach to digitizing the traces from large geomagnetic storms and highlight some of the issues to be aware of when capturing magnetic information from analogue measurements. These include cross-checking the final digitized values with the recorded hourly mean values from observatory year books and comparing several observatory records for the same storm to catch errors such as sign inversions or incorrect 'wrap-around' of data on the paper records.
地表地球磁场强度和方向的连续地磁记录可追溯到19世纪40年代。在过去的两个世纪里，英国有八个观测站，它们使用感光相纸测量每日的磁场变化，以生成模拟磁图。大约35万张磁图已被高分辨率数码拍摄。然而，将磁迹转换为数字值既困难又耗时，因为磁图可能存在线条重叠、记录质量低以及转换为国际单位制时元数据模糊等问题。我们讨论了将大型地磁暴的磁迹数字化的方法，并强调了从模拟测量中获取磁信息时需要注意的一些问题。这些问题包括将最终数字化值与观测站年鉴中记录的每小时平均值进行交叉核对，以及比较同一风暴的多个观测站记录，以发现诸如符号反转或纸质记录上数据“环绕”错误等问题。
