Chinese
Spanish
Russian
Portuguese
French
German
Indonesian
Thai
Vietnamese
Arabic
Italian
Turkish
Polish
Japanese
Radar commissioning can produce misleading error figures when the comparison measurement is less reliable than the instrument being assessed. A difference between two readings is not automatically radar error. The reference datum, reading resolution, surface movement and observation times all affect the comparison.
Qualify the Reference Before Radar Commissioning
Identify what the reference actually measures and where. A staff gauge near a disturbed inlet may see a different local surface from the radar. A delivered volume is not directly a level reference unless the vessel conversion and transfer conditions are established. Choose the method for the required test, not simply the nearest available number.
| Effect | Question | Action |
|---|---|---|
| Datum | Do both values refer to the same physical zero? | Survey or reconcile the references before calculating a difference. |
| Resolution | Can the reference distinguish the required change? | Do not report a finer conclusion than the method supports. |
| Timing | Did the surface move between observations? | Take paired readings or account for the measured movement. |
| Location | Are both methods observing a comparable surface? | Record positions and avoid treating local turbulence as instrument error. |
Why a Small Difference May Not Establish a Pass
Consider a test requiring assessment within a few millimetres, while the available reference can only be read confidently to about 10 mm. A displayed difference of 2 mm does not prove that the radar meets that requirement. The reference limitation must be reduced or the test conclusion explicitly restricted.
Timing can be equally important. As an illustrative calculation, a surface rising at 10 mm per second moves 30 mm during a three-second gap between observations. That apparent disagreement can exceed the instrument specification without indicating a radar fault. These figures describe the example, not MV-RD12 response performance.
MV-RD12 has a listed nominal accuracy of +/-2 mm. Do not use that figure as an installed acceptance tolerance without considering the agreed duty and measurement method. A formal uncertainty assessment may be needed where the acceptance decision depends on differences close to the reference capability.
Improve the Comparison Before Adjusting the Instrument
Repeat paired readings under stable, safely obtainable conditions. Record the spread rather than selecting only the closest pair. If disagreement varies with timing or surface disturbance, improve the test arrangement before applying an offset. Keep signed differences so a systematic shift is not hidden by averaging absolute values.
Reference-Method Questions
Q1. Is agreement between two radars independent proof?
Not necessarily. They may share a wrong datum or follow the same unwanted target. Use a reference whose principle, location and uncertainty are suitable for the decision, and document any common dependencies.
Q2. What should be done when no adequate reference is available?
State that the requested accuracy has not been demonstrated. Arrange an improved method or agree a limited functional test with its scope clearly identified. Do not convert a plausible display into a numerical accuracy claim.
Summary
Evaluate the comparison method before judging the radar. Include the datum, reference resolution, paired observation times and surface conditions in a commissioning measurement review request so adjustments are based on evidence rather than test noise.
