Publication Date:
2023-08-30
Description:
Extreme geomagnetic storms are likely to have catastrophic impacts to our modern increasingly technology-reliant society. Historical New Zealand magnetograms recorded on photographic paper from 1916 to 1991 (start of digital era) at the Amberley and Eyrewell geomagnetic observatories contain valuable information for statistical forecasting of extreme geomagnetic storms. To provide a digital long-term dataset as input for statistical models, the around 22,000 magnetograms that capture the continuous variations of the local Earth’s magnetic field D, H and Z components have been scanned into images at high resolution and are now being converted into digital values at a 1-minute resolution. We present our approach of using a combination of manual and automated digitisation techniques we have developed to translate the data from analogue traces into digital nanotesla values. The manual process that uses ArcGIS software as a tool focuses on the large geomagnetic storms with local k-index 7 and larger. We so far have captured 131 storm days from 1950-1990, with each storm taking up to 2 ½ hours of manual work. Software development (currently in MATLAB) for an automated “button-press” approach using image recognition techniques is targeting the lesser storms and quieter times. As part of quality control, the digitised values are cross-checked with published historical hourly mean values. The challenges we are encountering include hand-written notation, lack of labelling, gaps, offsets, overlapping and off-scale traces, varying line width and incomplete metadata.
Language:
English
Type:
info:eu-repo/semantics/conferenceObject
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