Abstract.A wireless sensor network deployment on a glacier in Iceland is described. The system uses power management as well as power harvesting to provide long-term environment sensing. Advances in base station and sensor node design as well as initial results are described.
The Glacsweb projectThe Glacsweb project [1] aimed to study glacier dynamics through the use of wireless sensor networks. It replaced wired instruments which had previously been used with radio-linked subglacial probes which contained many sensors. The base of a glacier has a large controlling effect on a glacier's response to climate change and there is a growing need to study it in order to build better models of their behaviour. Several generations of systems were deployed in Briksdalsbreen, an outlet of the Jostedal icecap in Norway. As a multi-disciplinary research project it involved people from many domains: electronics, computer science, glaciology, electrical engineering, mechanical engineering and GIS.Initial deployments had to solve the mechanical design of the probe cases and the unknown radio communication issues. The solutions involved craft as much as science and engineering but the key success has been to create data which had not existed before [2,3,4,5] while advancing our knowledge of sensor network deployments. Hot water drills are used in order to produce holes which reach the glacier bed. Most probes are placed 10-30cm under the ice while some are placed within the ice. Due to the relatively slowly changing environment the probe sense rate is normally set to once every four hours, although an adaptive sampling algorithm has been developed in the lab [6] which would optimise this sampling rate.
Iceland deploymentSkalafellsjökull is a part of the large Vatnajökull icecap in Iceland and our site was chosen at (64°15'27.09"N, 15°50'37.68"W) around 800m altitude near an access road. Although there was no local internet connection there was a mobile phone signal which we used for the main internet link. The glacier is deep enough to test beyond 100m depth in the future (we used 60-80m).Due to the nature of the team and time available a few key topics were chosen for the developments for the Iceland deployment. One main area was to improve the basestation design through the use of a Gumstix processor. This would provide a better development environment and easier package management. The probes would maintain the PIC18 microcontroller but would gain an improved power supply and simplified code. In terms of sensors the temperature needed to have smaller quanta in order to sense small changes. A light reflectance sensor was also on the list of items to be tested in order to provide more information on the nature of the material surrounding the probes. A simple star network was used rather than our more complex TDMA-based protocol [7] in order to simplify debugging.The disintegration of the ice front in Briksdalsbreen [8] meant that we lost our previous basestation infrastructure. This coupled with the higher altitude of the Icel...
