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City Sailingvideo
11. februar 2026 · 13 min · 623 visninger · Dover Harbour
Ferry Gotland alters course to dock at harbor
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Paul from City Sailing demonstrates ARPA (Automatic Radar Plotting Aid) in real traffic at Dover Harbour, using a live radar display cross-referenced with Actis to track multiple moving targets simultaneously.▶ 0:00 The radar is tuned at 12 miles, then stepped down to 1.5 miles on short pulse for better close-in definition, with the display set to North-up and stabilized.▶ 0:02 ARPA vector time is set to six minutes, then adjusted to two minutes and one minute to show where each target will be at those intervals.▶ 3:22 CPA and TCPA limits are zeroed for the demonstration to suppress alarms; Paul explains they should be set higher offshore.▶ 1:31 He distinguishes true vectors (red, showing absolute movement) from relative vectors (white/green, showing movement relative to own vessel) and stresses that relative mode is correct for collision avoidance under Rule 19.▶ 4:04 Targets include the USS Eagle, two cross-Channel ferries, a hovercraft, a square rigger, and inbound cargo ships doing 17–19 knots, with one showing CPA zero and TCPA 4.3 minutes.▶ 9:00 Paul recommends practicing ARPA first in good visibility so targets can be visually confirmed, then repeating the exercise at night and in fog.▶ 11:15
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