Ingelise Møller, GEUS - Geological Survey of Denmark and Greenland (Denmark)
Flemming Jørgensen, GEUS - Geological Survey of Denmark and Greenland (Denmark)
Verner Halskov Søndergaard, GEUS - Geological Survey of Denmark and Greenland (Denmark)
Esben Auken, University of Aarhus (Denmark)
Development of more time efficient and airborne geophysical data acquisition systems during the last decades have made large-scale mapping attractive and affordable in the planning and administration of e.g., groundwater or raw materials. The handling and optimised use of large amounts of geophysical data covering large areas requires a system, where data can easily be stored, extracted, interpreted, recombined and reused one time after the other. A system consisting of a high quality database, a tool for interpretation and analysis of data covering large areas and a way of visualising the data and the interpretations is the necessary answer to this requirement.
The only sustainable way to handle this challenge is to establish an integrated system, where the different tools in the system connect to, and interact with, each other in a transparent and intelligent manner. Work must be carried out directly on a copy of the database, and all relevant information on each data point and model must be accessible for use any time during the analysis and interpretation procedure.
Such a system has in Denmark been developed during the last decade. This system includes the GERDA (GEophysical Relation DAtabase) database and the Aarhus Workbench system. The GERDA database which is hosted by GEUS (The National Geological Survey of Denmark and Greenland) is Oracle based and covers the entire country. The Aarhus Workbench is a sophisticated tool working directly upon GERDA. The Aarhus Workbench facilitate different electrical and electromagnetic field-data to be imported, stored and extracted in GERDA by anybody who might be interested. Data can be processed, interpreted, analysed, evaluated and visualised in the Aarhus Workbench. The Aarhus Workbench, which also includes a GIS tool and facilities for geological interpretation, is developed by The Department of Earth Sciences, University of Aarhus during an ongoing cooperation with the authorities being responsible for the groundwater mapping.
The large amount of data stored in GERDA originate from mapping of raw materials and from a nationwide programme for groundwater mapping covering some 37% of Denmark. All collected data are continuously being uploaded to GERDA. More than 7500 km2 have by now been mapped, and geophysical measurements, particularly transient electromagnetic soundings (TEM), have been carried out in most of these areas at a high density rate. During the last 5 years most TEM have been carried out as SkyTEM measurements with a spacing of only 170 - 250 m between flight lines. The database now contains more than 300.000 TEM/SkyTEM soundings.
The integrated system of GERDA and the Aarhus Workbench is now used by all involved consulting companies as well as all authorities responsible for the groundwater mapping. The benefits of the large amount of geophysical data gathered in the GERDA database and utilised by the Aarhus Workbench are invaluable for all future groundwater planning and administration.