Parallel Indexing and Landfall

Question 1

Considerations for planning a safe landfall

Answer 1

• Any radar conspicuous objects to verify position when in range
• Objects available for determining position during day time (e.g. headland)
• Suitable lights or radio beacons for a night arrival
• Sufficient depth of water and area free of shoals and other nav hazards
• Position not affected by heavy traffic or fishing boats
• Position not affected by poor vis
• Position free from strong currents

Question 2

Considerations when determining a PI reference point

Answer 2

• Distance of object and likely radar range scale to be used at that time
• Drying heights that may affect the coastline and how it appears on the radar display
• Is the object fixed and radar conspicuous
• When no fixed objects are available the light vessel can be used but consideration must be given to the fact that it is not fixed

Question 3

Precautions when using PI techniques as per MGN 379

Answer 3

• Does not remove requirement for regular position fixing
• PI only indicate if vessel is left or right of tack not its progress along the track

Question 4

Checks when using PI techniques as per MGN 379

Answer 4

• Identity of fixed objects
• Radar, overall performance
• Gyro error and accuracy of heading alignment marker
• PI lines are correctly positioned and on a suitable display
• Accuracy of variable range markers, cursor and fixed range rings

Question 5

Accuracy of Radar

Answer 5

• 1°
• Range rings accurate to 30m or 1% of scale in use