Author(s): E. O. Lewis; B. W. Currie
Linked Author(s):
Keywords: No Keywords
Abstract: Ships navigating in an ice cover require information on the ice features and type being encountered in order to select a safe and optimum route. Most importantly, the ship must know the location of icebergs, multi-year ice floes and ridged first-year ice. Present marine radars do not adequately provide this information. The Canadian Department of Fisheries and Oceans and McMaster University have undertaken a program to improve the surface-based radar's ability to discriminate ice types and features. Three field experiments have been undertaken at a site overlooking the Northwest Passage. In the most recent experiment, radars were operated at 3 GHz (10 cm), 9 GHz (3 cm), 16 GHz (1.68 cm) and 35 GHz (0.96 cm), with the latter three providing both like and cross-polarized signals. To provide ground-truthing, the area of radar coverage was photographed with an aerial survey camera at scales of 1:20,000 and 1:8000. To provide the basis for comparison of radar parameters, ten lines oriented radially outward from the radar and passing through targets and ice of varying types were established. The radars were carefully aligned along each radial line and the radar returns for the various frequencies and polarisations were recorded. The paper describes the analysis, and compares the radar returns at various frequencies and polarizations. The radar returns as a function of range are compared with the aerial photography, showing that the radar can provide some surface topographic mapping capability. The 3 GHz radar was superior in highlighting areas of rough surface to be avoided, while cross-polarization at higher frequencies discriminated multi-year ice and icebergs from first-year ice. An ice navigation system is proposed which incorporates a single-polarized radar at 3 GHz and a dual-polarized radar at a higher frequency.
Year: 1984