Advanced HEM system for georisk assessment

The quality of the assessment of risks outgoing from environmental hazards strongly depends on the temporary and spatial distribution of the data gathered from the area of interest. Natural hazards generally emerge from wide areas, e.g. in the case of volcanoes or land slides. Conventional surface measurements (e.g. geoelectrics, seismics, etc.) are restricted to certain lines or locations and often can`t be conducted in difficult terrain. So they only give a spatial and temporally limited data set and consequently limit the reliability of the risk analysis. Aerogeophysical measurements potentially provide a valuable tool for completing the data set as they can be performed over a wide area, even above most difficult terrain within a short time. Especially helicopter based electromagnetic (HEM) measurement system form - beside aeromagnetics - a practical method to cover such areas in short time with penetration depths of up to about 150 metres. A most desirable opportunity in course of such measurements is to retrieve the dynamics of potentially hazardous environmental processes. This necessitates repeated measurements. Current HEM systems can`t accomplish this without periodical time and cost consuming calibration procedures due to their system immanent drift. Furthermore, slowly changing trends as occurring in the case of shallow basins can`t be resolved for the same reason. So, to advance a state of the art HEM-systems to a valuable tool for data acquisition in risk assessment or hydrological problem areas (and similar areas of activity) different measures have to be undertaken, which are the contents of the proposed project. The methodology bases on two paths: First, comprehensive experimental studies are scheduled on an existing HEM system serving as an experimental platform. This will be accomplished by logging a variety of relevant system- and environmental parameters, in course of ground tests an in flight. Also crucial hardware components will be substituted by laboratory equipment and controlled test series will be performed. The data will be analysed by means of signal theoretical and multivariate analysis techniques, so the sources of drift and noise can be identified. In parallel a numerical model will be adopted and continuously refined according to the results of the experimental studies. The model then will serve to simulate alternative configurations and analyse them due to their drift and noise behaviour. Finally, concepts for minimizing drift and noise will be developed. A joint inversion processing will be developed, which considers the additional measured parameters correlating closest to drift and noise. If highly nonlinear correlating a neural network will be trained with the test series data set, which is intended to predict the drift free signal. Hardware changes will be conducted as far as scheduled in project budget. If essential, further changes will be suggested in a report for future work. The advancement to an innovative high resolution, non-drifting system/processing will make the HEM-method to a valuable tool for improved risk assessment and develop a number of new fields of application.

The quality of the assessment of risks outgoing from environmental hazards strongly depends on the temporary and spatial distribution of the data gathered from the area of interest. Natural hazards generally emerge from wide areas, e.g. in the case of volcanoes or land slides. Conventional surface measurements (e.g. geoelectrics, seismics, etc.) are restricted to certain lines or locations and often can`t be conducted in difficult terrain. So they only give a spatial and temporally limited data set and consequently limit the reliability of the risk analysis. Aerogeophysical measurements potentially provide a valuable tool for completing the data set as they can be performed over a wide area, even above most difficult terrain within a short time. Especially helicopter based electromagnetic (HEM) measurement system form - beside aeromagnetics - a practical method to cover such areas in short time with penetration depths of up to about 150 metres. A most desirable opportunity in course of such measurements is to retrieve the dynamics of potentially hazardous environmental processes. This necessitates repeated measurements. Current HEM systems can`t accomplish this without periodical time and cost consuming calibration procedures due to their system immanent drift. Furthermore, slowly changing trends as occurring in the case of shallow basins can`t be resolved for the same reason. So, to advance a state of the art HEM-systems to a valuable tool for data acquisition in risk assessment or hydrological problem areas (and similar areas of activity) different measures have to be undertaken, which are the contents of the proposed project. The methodology bases on two paths: First, comprehensive experimental studies are scheduled on an existing HEM system serving as an experimental platform. This will be accomplished by logging a variety of relevant system- and environmental parameters, in course of ground tests an in flight. Also crucial hardware components will be substituted by laboratory equipment and controlled test series will be performed. The data will be analysed by means of signal theoretical and multivariate analysis techniques, so the sources of drift and noise can be identified. In parallel a numerical model will be adopted and continuously refined according to the results of the experimental studies. The model then will serve to simulate alternative configurations and analyse them due to their drift and noise behaviour. Finally, concepts for minimizing drift and noise will be developed. A joint inversion processing will be developed, which considers the additional measured parameters correlating closest to drift and noise. If highly nonlinear correlating a neural network will be trained with the test series data set, which is intended to predict the drift free signal. Hardware changes will be conducted as far as scheduled in project budget. If essential, further changes will be suggested in a report for future work. The advancement to an innovative high resolution, non-drifting system/processing will make the HEM-method to a valuable tool for improved risk assessment and develop a number of new fields of application.