Page 12 - Ranger Demo
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dynamic temporally and spatially. For example, multiple gliders can be instructed to fly to such locations with complementary flightpaths, resulting in excellent 3-dimensional coverage of the region of interest. As well as the academic community, the RN has been particularly interested in glider capability for improving their ocean forecast capability with this being the key objective of project HECLA. Figure 8 demonstrates one example from project HECLA to the north-west of Scotland, where the contoured and coloured areas of the figure show the wide-area ocean model forecast of the temperature structure, overlaid with the tracks of the two gliders within the 3D view (black and white tracks). In this instance, the gliders were instructed to begin to sample to a deeper depth (at about 3⁄4 of their way along the track). The purpose was to obtain data on the tactically significant temperature stratification feature predicted by the ocean model at about 1000m depth.
Figure 8 Model data provides continuous, high-resolution coverage of the 3D ocean. However, it needs to be ground-truthed against real observations. Here, the UK Meteorological Office AMM-15 model is sliced vertically, and two gliders are directed to sample feature predicted on the model during the 2020 HECLA exercise west of Scotland
Not All Plain Sailing
As with all oceanographic equipment, there is an inherent risk when deploying gliders. Missions can be compromised by biofouling (Figure 9), especially in shallow, biologically productive parts of the ocean. This fouling can affect both the accuracy of sensor data and vehicle performance.
Operation close to ice-covered areas is an obvious risk, but there have also been instances of damaged and lost gliders due to interactions with marine wildlife and ship traffic. A particular example of this is shown in (Figure 10) where a glider wing snapped
during a HECLA trial (unknown reason), but was still able to measure and transmit data and
Figure 9 A glider covered in biofouling (courtesy of Teledyne Webb Research)
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