Appendix 3 - Sensor errors
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Statutory Documents - IMO Publications and Documents - Resolutions - Assembly - IMO Resolution A.823(19) – Performance Standards for Automatic Radar Plotting Aids (ARPAs) – (Adopted on 23 November 1995) - Appendix 3 - Sensor errors

Appendix 3 - Sensor errors

The accuracy figures quoted in 3.8 of these standards are based upon the following sensor errors, and are appropriate to equipment complying with the performance standards for shipborne navigational equipment.

  • Note: s means ‘‘standard deviation’’.

Radar

Target glint (scintillation) (for 200 m length target)

  • Along length of target σ = 30 m (normal distribution)

  • Across beam of target σ = 1 m (normal distribution)

Roll-pitch bearing: The bearing error will peak in each of the four quadrants around own ship for targets on relative bearings of 045°, 135°, 225° and 315°, and will be zero at relative bearings of 0°, 90°, 180° and 270°. This error has a sinusoidal variation at twice the roll frequency.

For a 10° roll the mean error is 0.22° with a 0.22° peak sine wave superimposed.

Beam shape – assumed normal distribution giving bearing error with σ = 0.05°

Pulse shape – assumed normal distribution giving range error with σ = 20 m

Antenna backlash – assumed rectangular distribution giving bearing error ±0.05° maximum

Quantization

Bearing – rectangular distribution ±0.1° maximum.

Range – rectangular distribution ±0.01 nautical miles maximum.

Bearing encoder assumed to be running from a remote synchro giving bearing errors with a normal distribution s = 0.03°.

Gyro-compass

Calibration error 0.5°.

Normal distribution about this with σ = 0.12°.

Log

Calibration error 0.5 knots.

Normal distribution about this, 3σ = 0.2 knots.

Parent topic: IMO Resolution A.823(19) – Performance Standards for Automatic Radar Plotting Aids (ARPAs) – (Adopted on 23 November 1995)
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