Geosphysical Data Processing
GEOIMAGE specialises in processing airborne (and ground) geophysical surveys of all vintages. We use quality software (including Intrepid, Geosoft, ERMapper, Geomatica, ArcGIS, and MapInfo), and our staff have extensive experience in handling the good and the not-so-good digital data. Examples of some of the surveys we have worked on include re-processing and mosaicing the extensive publicly-released surveys from Australia, Canada and west and southern Africa.
Geophysical Data Integration
After carrying out all the preprocessing of your geophysical data sets including gridding, levelling, filtering, and mosaicking, we can then provide you with a complete set of integrated datasets. We can take all your raster datasets, which may include magnetic intensity, RTP magnetics, vertical derivatives of the magnetics, the radiometric channels, gravity, satellite imagery, etc and produce composite images that show the spatial relationships between the parameters. These composite images can be output as ECW compressed images that can be viewed in MapInfo or ArcView where they can be further integrated with your geological and other vector infomation. Alternatively we can make hardcopy from the images.
Examples of integrated datasets in the Georgetown region of Queensland.
- A. High U on vertical derivative magnetics.
- B. High U on EarthSat NaturalVue image.
- C. Composite radiometrics on 45az shade on TMI.
Data acquired by airborne geophysical surveys have been routinely stored on digital media and processed digitally since the late 1970s. However, in comparison to more recent surveys, these data are commonly seen to be inferior due to:
- Lower specification survey parameters like broader line spacing, increased terrain clearance, and smaller volume crystals for spectrometer surveys,
- Inaccuracies in the survey location data due to poor navigation and recovery and
- Difficulties in the digital processing due to lack of computing power and (by today’s standards) unsophisticated software and computing techniques.
Gridded representations of these earlier surveys are commonly characterized by:
- corrugations and “busts” due to poor tie-line levelling;
- crossing flight-lines and terrain clearance variation along lines;
- spikes due to inadequate diurnal corrections and poor processing;
- parallax and heading errors or introduced errors due to excessive filtering and smoothing of flight-line data by contractors.
The lack of separation between potassium, thorium, and uranium channels in spectrometer surveys is sometimes also a problem. In reality though, this earlier data is an invaluable resource. Careful re-processing can make any survey more interpretable, and allow easier extraction of relevant information. A re-processed survey with lesser specifications (or better still a careful mosaic of a number of these surveys) can provide a regional overview that facilitates interpretation of a structural setting, as well as providing the basis for better defining the parameters and location of “high-resolution” surveys over potential target areas, possibly suggesting airborne EM or airborne gravity as preferred or ancillary acquisitions. The re-processed survey may even serve in its own right (depending upon survey specifications) as a basis for detailed interpretation and information extraction.
An example of geophysical processing and mosaicing of multiple aeromagnetic surveys. Individual surveys were edited to correct obvious problems due to elevation errors, reflights, and noise spikes in the original data. Surveys were then microlevelled to a common base, and grid “stitched” at optimum cell size. This preserves high frequency information from surveys flown at closer line spacing. Data shown here is provided by the Northern Territory Geological Survey.
LEFT IMAGE: Total magnetic intensity (TMI) grid stitch of detailed state and federal government airborne surveys and company openfile airborne surveys. Background TMI is the Geoscience Australia terrestrial magnetics grid at 250 metre resolution. The state and federal government grids were downloaded from GADDS and the company openfile grids are held in GEOIMAGE’s archive.
RIGHT IMAGE: Background image is as per the image on the left and showing the detailed state government airborne surveys in blue, the detailed federal government airborne surveys in red and the openfile surveys in yellow used in the TMI grid stitch.