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Reported by Mal Heron
One innovation at ISIE was the Interactive Session where poster presenters were each given a 3-minute time slot to summarize their poster during an extended coffee break. It was very informal and some people did not listen; but many did. It was held in the foyer where the coffee was served with people coming and going. I thought it was an excellent feature without imposing on the schedule. Afterwards I went back to look more carefully at a couple of the posters.
Victoria Chapter Technical Meeting
Reported by Nick Hall-Patch
The earth’s magnetic field varies somewhat with time, and these variations affect the accuracy of modern navigation systems. Dr. Rasson described the network of magnetic observatories. maintained by various countries, as having an objective of establishing a “magnetic atlas” that records variations in the geomagnetic field. These observatories are land-based internationally, and must be accessible due to frequent recalibration. There are no true magnetic observatories located under the ocean at this time, so a comprehensive picture of the magnetic field over the Earth is not currently observable.
Dr. Rasson then described the set of instruments used in land based magnetic observatories, which includes a variometer to measure changes occurring along the three axes of the magnetic field, and a proton magnetometer, providing the modulus of the magnetic field. Additionally, there is a non-magnetic theodolite which provides the bearing of the field relative to true north, as well as its inclination with respect to the vertical.
Although he pointed out that there are presently magnetic observatories on small islands around the world, in addition to those on the continents, Dr. Rasson presented a rationale for placing additional observatories on the ocean floor. Scientific research would benefit from the resultant quantity and quality of magnetic field data, particularly at high latitudes where geomagnetic field variations are more intense. Improved magnetic field modeling could lead to greater understanding of the physics of the deep Earth, as well as of such phenomena as the south Atlantic anomaly, in an area of the world where the strength of the magnetic field is considerably lower than elsewhere.
Dr. Rasson also discussed how tsunamis and underwater earthquakes create perturbations in the Earth’s magnetic field. These pertubations could be identified by ocean-based observatories and provide earlier warnings to the public about these events.
Finally, greater accuracy in geomagnetic field observations provided by ocean floor-based observatories could benefit industry, by integrating acquired data into the products employing magnetic declination for compass correction. Dr. Rasson pointed out, as an example, that more accurate local geomagnetic field information could ensure more precise positioning for drilling undersea oil wells.
There are some notable obstacles associated with deploying present magnetic observatory sensors under the ocean. In addition to the standard concerns associated with placing instrumentation on the sea floor, such as power, communications, corrosion, extreme water pressure, et al, there are other issues for the observatories. These include the need to be in a non-magnetic environment, to have an autonomous ability to derive the direction of true north, and to perform self-leveling. Unlike surface observatories, all orientation of the instrumentation needs to be automated.
Dr. Rasson continued by describing some technical solutions to the problems associated with creating underwater magnetic observatories. The use of a fluxgate variometer provides low-noise measurements of the magnetic field vector changes with a high sampling rate. Together with a proton magnetometer, this provides the absolute measurement of the field’s modulus. A non-magnetic theodolite, equipped with a fluxgate and a fiber optic gyro, provide an indication of true and magnetic North as well as magnetic inclination. The levelling of the system is accomplished with software rather than by using motorized leveling screws.
The use of commercial products in the design of the underwater observatory required some modifications in order to meet desired specifications. The total resulting package was low powered enough to be suitable for battery operation, and could communicate via an acoustic modem.
A question and answer time followed the presentation. Among the issues discussed were the impact of ocean currents and underwater electrical cables on the observed magnetic fields.