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Welcome to the official website of the mgd77 project!

Here you can find documentation on our marine geophysical quality control methods, download errata tables reviewed to date, and find links to other associated software and documentation.

About the mgd77 project:

The mgd77 project aims to clean up the Marine Geophysical Trackline Database which is maintained by the National Centers for Environmental Information (formerly the National Geophysical Data Center) and is home to ~6,130 marine geophysical data sets collected by government and academic institutions since the early 1950s.

For this task we devised along-track analysis, a system for detecting extreme errors and correcting erroneous data sets without impacting the majority of observations [3--8]. Extreme errors are detected by checking for unreasonable navigation, checking reported against recomputed magnetic and gravity anomalies, and by comparing reported data with reference values such as satellite derived gravity and predictive bathymetry grids, among other tests. Detected errors are output systematically in the E77 errata table format. The errata table is reviewed by an analyst who determines which correction flags to apply. The errata table is then ingested along with original data allowing corrected data to be output on-the-fly and without overwriting original files.

We then applied along-track analysis to ~5,280 surveys archived at NCEI on a case-by-case basis [7]. The time consuming study yielded error reductions comparable to other studies which employed crossover analysis to detect and reduce errors. Whereas all observations are changed by the crossover correction approach, along-track analysis only affects values flagged by a reviewer. Furthermore, crossover corrections only apply to included tracks and become outdated as new survey data become available. Hence along-track analysis is a more empirical approach which should precede crossover analysis.

Submittal of erroneous data continues to the present day therefore it appears that more data scrutiny needs to be concentrated during data acquisition [8]. We are therefore proposing a new system for quality assessment and control at sea using along-track analysis combined with other approaches including multibeam processing via MB-System, crossover analysis, and new at-sea survey management and visualization tools known as SURVEY (links below).

mgd77 project overview:

PhaseStatusCitation
  • Along-track analysis software development
  • (complete)[1][2][3][4][5][6]
  • Manual review of archived marine geophysical surveys using along-track analysis
  • (complete)[6][7]
  • Assessment of the along-track approach
  • (complete)[6][7]
  • Application to quality control at sea
  • (active)[8]
  • Producing marine geophysical archive files from raw underway data
  • (active)[9]

    This ongoing research is supported by the National Science Foundation.

    Call for collaboration

    We have only initiated new community infrastructure and applied it to existing data sets to obtain first generation error correction tables and correction methods. Given the vast number of marine geophysical data sets, both past and present, we invite other researchers to join in the effort so that we can improve error detection methods and further reduce errors in marine geophysical data sets.

    Relevant Citations:

    1. Hamilton, M, Wessel, P, Luis, J, Taylor, B, and Ko, YT (2019): The seagoing scientist’s toolbox: Integrated methods for quality control of marine geophysical data at sea, Geochem. Geophys. Geosys, 20, 1–10. https://doi.org/10.1029/2018GC007891.
    2. Hamilton, M, Wessel, P, Taylor, B, and Luis, J (2019): Producing marine geophysical archive files from raw underway data,Comp & Geosci,133, http://doi.org/10.1016/j.cageo.2019.104321.
    3. Chandler, M. T., and P. Wessel (2012), Errata-based correction of marine geophysical trackline data, Geochem. Geophys. Geosyst., 13, Q10004, doi:10.1029/2012GC004294.
    4. Chandler, M. T.  (2011), Tectonic history of the Greater Ontong Java Plateau and Errata-based correction of marine geophysical trackline data. Ch. 4, PhD Dissertation, University of Hawaii. (51.5 MB PDF)
    5. Chandler, M. T., and P. Wessel (2008), Improving the quality of marine geophysical track line data: Along-track analysis, J. Geophys. Res., 113, B02102, doi:10.1029/2007JB005051.
    6. Chandler, M. T., and P. Wessel, (2007), Fall 2007 AGU Poster (7.5 MB PDF)
    7. Wessel, P., and M. T. Chandler, (2007), The mgd77 Supplement to the Generic Mapping Tools. Computers & Geosciences, 33, 62-75.
    8. Chandler, M. T.  (2006), Improving the Quality Control of Marine Geophysical Trackline Data. MS Thesis, University of Hawaii. (8.0 MB PDF)
    9. Chandler, M. T., and P. Wessel, (2004), Fall 2004 AGU Poster (7.0 MB PDF)

    Contributors:

  • Dr. Michael Hamilton
    Affiliate Researcher
    Department of Geology & Geophysics
    University of Hawaii

  • Dr. Paul Wessel
    Professor of Geology & Geophysics
    University of Hawaii

  • Dr. Joaquim Luis
    Professor of Geophysics
    University Algarve

  • Links:

  • The SURVEY Tools
  • SURVEY home page
  • The Generic Mapping Tools
  • GMT home page
  • NCEI Trackline Geophysics 
  • GMT home page
  • Google Earth
  • Google Earth home page
  • National Science Foundation
  • NSF home page

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    Maintained by Michael Hamilton ○ Last modified: November 05 2019.