On the study of comprehensive airborne survey system for geothermal structure

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We conducted fundamental study for improving the depth of investigation, resolving ability and accuracy of airborne electromagnetic, magnetic and infrared image survey aiming at practical application for a geothermal survey. The study was carried out to investigate practically some issues through field survey using helicopter at some geothermal fields. The major results of each method was indicated as follows.As for the airborne electromagnetic, we developed instrument and data processing method of grounded electrical source airborne electromagnetic to increase the depth of investigation up to several kilometers. To observe magnetic response of the ground in the air, we developed high accuracy flux-gate magnetometer. The fiber optic gyros attached to the attitude measurement equipment was used to measure pitch and roll of the magnetometer, which were using collection of the motion of magnetometer. We obtained expected data using practical set up in the field test survey.We improved proton magnetometer to detect small magnetic field change due to geothermal structure with the airborne magnetic survey. We also developed the method measuring vertical gradient of the field. To increase the accuracy, we developed new circuit for exciting strong proton signal. And we contrived a circuit to adjust timing of measurement between magnetic and electromagnetic methods.To improve the accuracy of estimating heat discharge using airborne infrared image, we investigated characteristics of the data obtained in the air in comparison with surface data. We also developed data processing method for wide data.