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I have downloaded an EM survey data pack recently and within the zip file it contains:

  • Final_EM.des - header file describing contents of the located data
  • Final_EM.dfn - Channel definition file containing info on located data in the *.dat file
  • Final_EM.dat - Flat ascii file containing located EM, magnetic and digital terrain data
  • Final_EM.gdb - Geosoft database file containing located EM, magnetic and digital terrain data

I am trying to upload the EM data files onto QGIS so that I can visualise it against some other geological data files.

I have trying dragging and dropping, tried uploading as a vector layer, raster, it does not seem to be able to load up.

Just wondering if there is anyone here that could help me out?

Snaileater
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david Lim
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2 Answers2

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You haven't given detail so this could be airborne EM (Electromagnetic data) or ground EM or down-hole EM. The first 3 files are information and source files. The gdb file contains located data, so this is all you need. Qgis can certainly open gdb files, and the layers in there are probably in point data format, so vectors. Choose "Add vector layer", "Source Type = Directory" and source should be either "OpenFileGDB" or "ESRI FileGDB" (I don't know which format Geosoft uses). If you cannot access the gdb file then try to unzip it first.

Note that (as you may already know) EM data is much trickier for a non-geophysicist to interpret than is, for example, magnetic data. You might need to come up with some color coding or even imaging to make sensible comparisons with geology data.

Leigh Bettenay
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You can also create a point database in QGIS using delimited text import of the dat file with regex capture groups, e.g. (.{16})(.{15})(.{12}). See Importing DAT file with different space width delimiter in QGIS 3

LSgeo
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