SavedAdd your journal

Journals / International Journal of Environment and Geoinformatics / 2026 / Volume: 13 Issue: 2

Automated Digitization and Integration of Legacy Geophysical Maps: A Reproducible Python Workflow for Analog Archive Recovery Applied to the Southern Marmara Sea, Türkiye

Muhammet Ali Aygün(ISTANBUL UNIVERSITY)0000-0002-8580-3536
Ahmet Sinan Demirel(ISTANBUL UNIVERSITY)0000-0001-5291-0493
Pages
—
Publication Date
2026-06-19
🏛️Bibliographic metadata and full text access for this article are provided via DergiPark.
DergiPark Record ↗
✨

AI Summary & Key Takeaways

AI Insight
⚡ TL;DR(Too Long; Didn't Read)

The fully open-source Python code is made available for the reproducible recovery of printed archives on a global scale.

📌 3 Key Takeaways

🎯
Objective & Hypothesis:In many national geophysical surveys performed during the period from the 1950s to the 1990s, large analog archives are still not accessible to modern analysis techniques because of their printed, non-digital form.
📊
Key Findings & Data:The study analyzes 27 printed maps, including 15 gravity and 12 magnetic maps, from 1972 to 2000, created by three different agencies (MTA General Directorate, C&K Petroleum, Norexplo Consultant) using two self-developed Python modules.
💡
Conclusion & Impact:The fully open-source Python code is made available for the reproducible recovery of printed archives on a global scale.
🔬Design:Survey & Empirical Study
📍Scope:2000 Verileri
⚙️Variables:Legacy Data Digitization · Bouguer Gravity · Magnetic Anomaly

Abstract

In many national geophysical surveys performed during the period from the 1950s to the 1990s, large analog archives are still not accessible to modern analysis techniques because of their printed, non-digital form. This paper presents a Python-based, fully automated workflow for the systematic digitization, georeferencing, and multi-source integration of legacy gravity and magnetic survey maps, applied to a critical geophysical archive in the southern Marmara Sea region of Turkey. The study analyzes 27 printed maps, including 15 gravity and 12 magnetic maps, from 1972 to 2000, created by three different agencies (MTA General Directorate, C&K Petroleum, Norexplo Consultant) using two self-developed Python modules. The fully digitized database contains 24,510 Bouguer gravity measurements (86 survey lines) and 25,230 reduced-to-pole (RTP) magnetic measurements (87 survey lines), amounting to 49,740 integrated data points. Cross-validation for the gravity data set gives r = 0.9996 and RMS = 0.426 mGal, and for the magnetic data set r = 0.9991 and RMS = 7.485 nT, with mean residuals close to zero in both cases, indicating the absence of systematic errors. The reconstructed Bouguer gravity field varies from −37.47 to +74.01 mGal, and the RTP magnetic field from 746.5 to 2085.6 nT over the study area (27.0–29.4°E, 40.2–40.7°N), resolving anomaly patterns at a resolution of 150-200 m, roughly 10-20 times higher than the resolution of global maps available so far. The spatial coverage is above 99% for both data sets. The workflow reaches an accuracy of 94-97% in contour recognition and saves up to 80-90% of processing time compared to manual digitization. The fully open-source Python code is made available for the reproducible recovery of printed archives on a global scale.

🔖

Cite This Article

Aygün, M. A., Demirel, A. S. (2026). Automated Digitization and Integration of Legacy Geophysical Maps: A Reproducible Python Workflow for Analog Archive Recovery Applied to the Southern Marmara Sea, Türkiye. International Journal of Environment and Geoinformatics, Volume: 13 Issue: 2. https://doi.org/10.26650/ijegeo.1910698

📄 Full Text PDF Viewer

📄

PDF görüntüleyici hazırlanıyor...

References (26)

  1. Aktaş G, Hisarlı ZM, Demirel AS (2023) Interpretation of the tectonic structure of Gemlik Bay using magnetic data. Tectonophysics 863:229981. https://doi.org/10.1016/j.tecto.2023.229981
  2. Ateş A, Kayıran T, Sincer I (2003) Structural interpretation of the Marmara region, NW Turkey, from aeromagnetic, seismic and gravity data. Tectonophysics 367:41–99. https://doi.org/10.1016/S0040-1951(03)00044-1
  3. Aygün MA, (2025). Investigation of The Structural Elements of The South of The Marmara Sea By Integrated Geophysical Methods (PhD Thesis). Istanbul University, Istanbul, Turkey.
  4. Aygün, M. A., and Demirel, A. S. (2024). Imagıng the Crustal Structure of the Southern Marmara Region (Turkey) Using Aeromagnetic and Gravitational Data. International Journal of Environment and Geoinformatics, 11(4), 101-108. https://izlik.org/JA49CY77MX
  5. Balmino, G., Vales, N., Bonvalot, S., & Briais, A. (2012). Spherical harmonic modelling to ultra-high degree of Bouguer and isostatic anomalies. Journal of Geodesy, 86(6), 499–520. https://doi.org/10.1007/s00190-011-0533-4
  6. Bhattacharyya, B. K., & Chan, K. C. (1977). Computation of gravity and magnetic anomalies due to inhomogeneous distribution of magnetization and density in a localized region. Geophysics, 42(3), 602–609. https://doi.org/10.1190/1.1440731
  7. Bingham RG, Bodart JF, Durand G et al. (2021) Inferring ice-sheet geometry from acoustic returns from the bed of Pine Island Glacier, West Antarctica. J Geophys Res Earth Surf 126:e2021JF006242.
  8. Demirel AS, Alp H, Alpar B, Vardar D (2021) Discussion of the fault models of the northern Marmara shelf and the lagoon Küçükçekmece with new marine magnetic data, Turkey. Thalassas 37:427–436. https://doi.org/10.1007/s41208-020-00275-7
  9. Demirel AS, Alpar B, Yaltırak C, Vardar D, Kurt H (2020) Northern segment of the North Anatolian Fault in the Gulf of İzmit inferred from marine magnetic anomalies. Mar Geophys Res 41:6. https://doi.org/10.1007/s11001-020-09401-5
  10. Gazioğlu, C., Gökaşan, E., Algan, O., Yücel, Z., Tok, B., & Doğan, E. (2002). Morphologic features of the Marmara Sea from multi-beam data. Marine Geology, 190(1-2), 397-420.
  11. Gholamrezaie E, Scheck-Wenderoth M, Sippel J, Strecker MR (2019) Crustal structure of the southern Marmara region from 3D integrated gravity modelling. Tectonophysics 768:228168. https://doi.org/10.1016/j.tecto.2019.228168
  12. Gokaşan, E., Ustaömer, T., Gazioğlu, C., Yucel, Z. Y., Öztürk, K., Tur, H.,. & Tok, B. (2003). Morpho-tectonic evolution of the Marmara Sea inferred from multi-beam bathymetric and seismic data. Geo-Marine Letters, 23(1), 19-33.
  13. Hébert, H., Schindele, F., Altinok, Y., Alpar, B., & Gazioglu, C. (2005). Tsunami hazard in the Marmara Sea (Turkey): a numerical approach to discuss active faulting and impact on the Istanbul coastal areas. Marine Geology, 215(1-2), 23-43.
  14. Hilditch, C.J. (1969). Linear skeletons from square cupboards. In B. Meltzer & D. Michie (Eds.), Machine Intelligence IV (pp. 403-420). Edinburgh: University Press.
  15. Hilditch, C.J. (1983). Comparison of thinning algorithms on a parallel processor. Image and Vision Computing, 1(3), 115-132. https://doi.org/10.1016/0262-8856(83)90063-X.
  16. Kanungo T, Haralick RM, Storch I (2021) A framework for large-scale automated digitization of geologic maps. Comput Geosci 152:104770.
  17. Kende J, Henry P, Bayrakci G, Özeren MS, Grall C (2017) Moho depth and crustal thinning in the Marmara Sea region from 3-D gravity inversion. J Geophys Res Solid Earth 122:1374–1393. https://doi.org/10.1002/2015JB012735
  18. Lacoste, A., Cressie, N., Cotter, D., Guo, D., & Hadden, D. (2021). Systematic evaluation of analog geophysical map digitization: Accuracy, efficiency, and transferability of automated contour extraction workflows. Computers & Geosciences, 157, 104930. https://doi.org/10.1016/j.cageo.2021.104930
  19. Le Pichon, X., Chamot-Rooke, N., Rangin, C., & Şengör, A. M. C. (2003). The North Anatolian fault in the Sea of Marmara. Journal of Geophysical Research: Solid Earth, 108(B4), 2179. https://doi.org/10.1029/2002JB001862
  20. Meyer, B., Saltus, R., & Chulliat, A. (2017). EMAG2: Earth Magnetic Anomaly Grid (2-arc-minute resolution) Version 3. National Centers for Environmental Information, NOAA. https://doi.org/10.7289/V5H70CVX
  21. Otsu, N. (1979) A Threshold Selection Method from Gray Level Histograms. IEEE Transactions on Systems, Man, and Cybernetics, 9, 62-66. https://doi.org/10.1109/TSMC.1979.4310076
  22. Sandwell, D. T. (1987). Biharmonic spline interpolation of GEOS-3 and SEASAT altimeter data. Geophysical Research Letters, 14(2), 139–142. https://doi.org/10.1029/GL014i002p00139
  23. Tararbra M, Samokhin A, Nikitenko M (2019) Automated recognition and digitisation of geological contour maps: a neural network approach. Comput Geosci 128:33–42.
  24. Vardar D, Alp H, Demirel S, Aykurt Vardar H, Alpar B (2021) Offshore/onshore correlation of the North-Anatolian fault deformations in the western Sea of Marmara. Nat Hazards 107:1905–1923. https://doi.org/10.1007/s11069-021-04551-y
  25. Vardar D, Öztürk K, Yaltırak C, Alpar B, Tur H (2014) Late Pleistocene–Holocene evolution of the southern Marmara shelf and sub-basins: middle strand of the North Anatolian fault. Mar Geophys Res 35:69–85. https://doi.org/10.1007/s11001-013-9201-5
  26. Gokaşan, E., Ustaömer, T., Gazioğlu, C., Yucel, Z. Y., Öztürk, K., Tur, H.,. & Tok, B. (2003). Morpho-tectonic evolution of the Marmara Sea inferred from multi-beam bathymetric and seismic data. Geo-Marine Letters, 23(1), 19-33.