Navigation Electronics & GMDSS Flashcards
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Read the first 7 Navigation Electronics & GMDSS flashcards as text
What does AIS stand for in the context of marine navigation equipment?
Answer: Automatic Identification System
AIS stands for Automatic Identification System; it automatically broadcasts vessel identity, position, speed, and course data to nearby ships and shore stations via VHF.
On which VHF channels does Class A AIS operate for its transmissions?
Answer: Channels 87B (161.975 MHz) and 88B (162.025 MHz)
Class A AIS transmits alternately on VHF channels 87B (161.975 MHz) and 88B (162.025 MHz), which are internationally designated solely for AIS use.
Which radar frequency band provides the best target resolution for close-range navigation in congested waters?
Answer: X-band (9-10 GHz)
X-band radar (9-10 GHz) uses shorter wavelengths that produce superior target discrimination and range resolution, making it the preferred band for coastal and harbor navigation.
What is the primary function of ECDIS aboard a vessel?
Answer: Electronic Chart Display and Information System used as an approved navigation system
ECDIS (Electronic Chart Display and Information System) displays official Electronic Navigational Charts and integrates position, radar overlay, and route planning data as an approved replacement for paper charts.
What does the ARPA CPA/TCPA alarm warn the officer of the watch about?
Answer: A tracked target whose closest point of approach or time to CPA falls below preset alarm thresholds
The CPA/TCPA alarm activates when ARPA calculates that a tracked target will pass within the preset minimum CPA distance or within the set TCPA time, alerting the officer to a potential collision risk.
Which data must be manually entered into a Class A AIS transponder by the bridge crew?
Answer: Destination, ETA, draught, and other voyage-related data
Voyage-specific information such as destination port, estimated time of arrival, and draught must be manually entered into the AIS transponder, while position and speed are fed automatically from connected sensors.
What does ARPA stand for as fitted on modern navigational radar systems?
Answer: Automatic Radar Plotting Aid
ARPA (Automatic Radar Plotting Aid) automatically acquires, tracks, and computes the CPA and TCPA of radar targets to assist officers with collision avoidance decisions.