This report describes the survey operation, survey and processing methods and the deliverables of an aerogeophysical survey in Olkiluoto area in April 2008.
The survey was conducted by Geological Survey of Finland (GTK). The survey aircraft was a twin-engine Twin Otter operated by Finnish Aviation Academy (SIO) and owned by Natural Environment Research Council / British Geological Survey (NERC / BGS), with whom GTK has established a joint venture called Joint Airborne-geoscience Capability (JAC).
The survey was conducted in April 2008 during six days. The survey consists of six separate survey flights, one of which was a magnetic calibration flight. The survey was based in Pori airport. Survey line spacing was 50 meters and nominal survey altitude was 30 meters. Measurements were completed in April 2008, and data processing and reporting was done in June 2008.
Two cesium magnetometers installed onboard the aircraft (at the left wingtip and in a nose cone) were measuring the magnetic total field intensity during the survey flights. An automatic compensation unit corrected the aircraft attitude errors in the magnetic data in real time.
In addition to magnetic measurement, auxiliary parameters such as flight altitude and aircraft attitude were also recorded simultaneously. Reference ground base station was used for recording the temporal variations in the magnetic field and also reference data for post-positioning of coordinate information.
In the post-processing phase, heading correction, base station correction and microlevelling procedures were applied to the magnetic data. The data was exported to numeric XYZ files and interpolated into grid data file.
A noteworthy local detail present in the survey and in the processing was the massive power line. For safety reasons, flight altitude had to be increased and survey lines had to be cut short in the vicinity of the powerline. However, due to reasonable planning of the survey area boundaries, this caused no great damage to the end result.