Yachtmaster revision module 19 of 20

GPS

Electronic Navigation

Yachtmaster-level use of GNSS, chart plotters, electronic charts, radar, AIS, alarms, and backup navigation.

GNSS integrity, WGS84 datum, DOP, multipath, jamming, and spoofingChart plotter route checks, waypoint placement, and cross-track limits

18 guided lessons · 24 practice questions · 25 flashcards

3 outcomes · self-guided revision
  • Explain yachtmaster-level use of GNSS, chart plotters, electronic charts, radar, AIS, alarms, and backup navigation.
  • Apply GNSS integrity, WGS84 datum, DOP, multipath, jamming, and spoofing to a realistic onboard situation.
  • Recall the core check: electronic systems support, not replace, navigation.

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Lesson summaries

Use this module hub to choose the right lesson, then open the dedicated lesson page for the complete explanation, worked examples, FAQs, and practice questions.

Electronic Navigation Mindset

Electronic navigation is an aid to navigation, not a separate standard of seamanship. A Yachtmaster-level navigator uses GNSS, chart plotters, radar, AIS, depth, log, compass, and visual...

  • Electronic systems support, not replace, navigation
  • Cross-check with independent evidence
Read the full lesson: Electronic Navigation Mindset

GNSS Integrity and Datum

GNSS positions are usually referenced to WGS84, but charts may have a different or imperfect datum. Modern UKHO charts are normally compatible, yet older charts, harbour plans, and some f...

  • Most GNSS positions use WGS84
  • Check chart datum warnings
Read the full lesson: GNSS Integrity and Datum

Chart Plotter Route Checking

A route plotted electronically must still be appraised like a paper route. Check the entire track at the largest practical scale, especially around waypoints, headlands, drying banks, ove...

  • Check the whole route at large scale
  • Zoomed-out screens hide dangers
Read the full lesson: Chart Plotter Route Checking

Electronic Charts

Electronic charts are not all the same. Official Electronic Navigational Charts (ENCs) are vector charts designed for ECDIS and approved systems. Raster charts are scanned or image-based...

  • ENC: official vector chart data
  • Raster chart: image-style chart display
Read the full lesson: Electronic Charts

Alarms and Waypoint Management

Electronic alarms are useful only if they are configured sensibly and understood by the crew. Cross-track error, depth, anchor, AIS CPA/TCPA, arrival, and guard-zone alarms can all reduce...

  • Set alarms deliberately before departure
  • Avoid alarm fatigue
Read the full lesson: Alarms and Waypoint Management

Radar Set-up and Tuning

Radar performance depends on the set-up. Range scale, gain, sea clutter, rain clutter, tuning, heading alignment, and display mode all affect what you see. A poorly tuned radar may miss s...

  • Use an appropriate range scale
  • Tune gain and clutter controls carefully
Read the full lesson: Radar Set-up and Tuning

Radar Fixing and Parallel Indexing

Radar range is usually more accurate than radar bearing on a yacht set. A radar fix from two or more ranges to identifiable charted objects can be very reliable. Use variable range marker...

  • Radar range is often more accurate than radar bearing
  • Use two or more ranges for a radar fix
Read the full lesson: Radar Fixing and Parallel Indexing

Collision Assessment with Radar

Radar can show whether a contact is closing and whether the bearing is steady. A constant bearing with decreasing range indicates collision risk. MARPA or ARPA may calculate CPA and TCPA,...

  • Constant bearing and decreasing range means collision risk
  • CPA: closest point of approach
Read the full lesson: Collision Assessment with Radar

AIS CPA and Limitations

AIS broadcasts a vessel's identity, position, course, speed, and other data. Plotters can calculate CPA and TCPA from AIS targets, making AIS extremely useful for identifying ships and pl...

  • AIS helps identify traffic
  • CPA and TCPA support early collision assessment
Read the full lesson: AIS CPA and Limitations

Failure Planning and Redundancy

A Yachtmaster passage plan should include what happens if the plotter, GNSS, radar, AIS, depth sounder, log, or charging system fails. The answer may be paper chartwork, backup handheld G...

  • Plan for electronic failure before departure
  • Carry backup position and plotting methods
Read the full lesson: Failure Planning and Redundancy

Sensor Independence and Common-Mode Failure

Two displays are not necessarily two independent sources. A chart plotter, AIS overlay, DSC radio, tablet, and autopilot may all receive position from the same GNSS antenna or network. If...

  • Several screens may repeat one sensor and one error
  • Identify the source, power, network, and failure mode behind each value
Read the full lesson: Sensor Independence and Common-Mode Failure

Safety Depth, Contours and Display Configuration

A vector-chart display is a filtered view of a database. Safety depth, safety contour, shallow contour, deep contour, category layers, and scale determine which dangers are emphasised. Sm...

  • Derive display settings from draught, UKC, tide, squat, and uncertainty
  • Know how the fitted plotter selects and displays contours
Read the full lesson: Safety Depth, Contours and Display Configuration

Worked Radar Closing Assessment

A contact bears 045° relative at 6.0 NM. Three minutes later it still bears 045° relative but is at 5.0 NM. The near-constant relative bearing and decreasing range indicate collision risk...

  • One nautical mile closed in three minutes equals 20 kn relative closing speed
  • Five nautical miles at 20 kn gives a nominal 15-minute zero-range time
Read the full lesson: Worked Radar Closing Assessment

Restricted Visibility: Evidence, Rule 19 and Command

In or near restricted visibility, safe speed and a proper lookout are the starting conditions, not optional responses after a target appears. Have engines ready for immediate manoeuvre, d...

  • Rule 19 governs vessels not in sight in or near restricted visibility
  • Use safe speed, lookout, lights, signals, engines, radar, and position evidence together
Read the full lesson: Restricted Visibility: Evidence, Rule 19 and Command

GNSS Anomaly and Spoofing Response

Warning signs include an unexplained position jump, impossible course or speed, several vessels appearing displaced from radar echoes, a charted buoy shown on land, loss of time agreement...

  • A plausible display can still contain a false GNSS position
  • Protect sea room and disengage position-dependent automation first
Read the full lesson: GNSS Anomaly and Spoofing Response

Electronic Watch Handover and Configuration Control

A watchkeeper needs more than the active waypoint. Handover should cover the current fix and its evidence, course and speed, cross-track trend, next alteration, traffic and CPA concerns,...

  • Handover the evidence, limits, alarms, defects, and call-the-skipper triggers
  • Log route and sensor changes that alter the navigation picture
Read the full lesson: Electronic Watch Handover and Configuration Control

Yachtmaster Offshore Standard

Electronic Navigation at Yachtmaster level is not just recall. The answer has to show command judgement, evidence quality, margin, and a fallback if the first plan stops being safe.

  • State the evidence you trust and the evidence you distrust.
  • Name the margin that makes the plan defensible.
Read the full lesson: Yachtmaster Offshore Standard

Advanced Scenario Check

Decision pressure: The approach is narrowing, so the decision must be made before the last safe turn.

  • Apply GNSS integrity, WGS84 datum, DOP, multipath, jamming, and spoofing to a changed real-world situation.
  • Separate fact, estimate, and assumption.
Read the full lesson: Advanced Scenario Check

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