Measurement of outdoor gamma dose distribution with a multicopter

By using geoinformatics methods it is possible to use a non-imaging detector in the conventional sense to obtain a dose distribution image from a specific area. To produce coverage of the area’s planar dose distribution, there is a need for discrete radiation measurements over the area in an even raster and to assign planar coordinates to these measured values. Assuming that the measured radiation does not show a rapid change between the measurement locations, the desired dose distribution coverage can be produced with the interpolation of the measured values. The coordinates of the measurement points can be used to calibrate the coverage. The calibrated and georeferenced coverage is capable of detecting and locating a radiation source hidden or lost in an area. The advantage of the developed method is that measurements can be conducted using a small-sized multicopter, therefore it is cost-efficient and broadly applicable. The flight time of small-sized multicopters is very limited, so increasing the efficiency of the measurement is especially important. Practical comparisons of several methods regarding the measurement procedure were made during the experiments. Similarly, based on measurement experiences, the detector system was developed and tested in three main steps. These improvements have resulted in a detector system with a total weight of 500 grams including a battery capable of operating the detector for at least 120 minutes. The device is capable of detecting an average of 30 events per minute at 0.8ms background radiation. Experiments have shown that the system can significantly detect a source of 300 μSvh with a scan flight at 10m from ground level.