Pelorus

Pelorus assembly

Record evidence that the object provides a sighted bearing against an established angular reference.

1. Which components supply the graduated scale, target sight and reference index? definition
2. Is this a complete pelorus, a bearing-circle accessory or a heading-producing compass? boundary

Name and variant

Keep the conventional passive instrument interpretation distinct from documented broader uses of the name.

1. Which registry provenance, manual or collection record identifies this as a nautical pelorus? provenance
2. Does any heading-fed variant belong within this entry or require a relation to a separate compass model? boundary

Reading convention

Record the actual scale and distinguish its resolution from demonstrated measurement accuracy.

1. What angular range, numbering direction and smallest division does the scale show? measurement
2. Which index is read, and how is its zero related to the vessel's bow or another declared direction? definition

Bearing conversion

Require explicit conventions, contemporaneous heading and correction status before deriving a true, magnetic or compass-referenced bearing.

1. Which heading source and reference frame support this bearing, and when was that heading observed? provenance
2. Which angular convention and corrections must be applied before combining heading and relative bearing? action
3. Was the card already heading-set, making another heading addition erroneous? boundary

Station reference

Record alignment evidence for the actual mount rather than assuming every observing position shares the same zero.

1. How is this mount aligned with the vessel's fore-and-aft direction, and what offset was measured? measurement
2. Which alignment and retention checks are required after moving or reinstalling the pelorus? action

Usable observation envelope

Record levelling or gimbal provisions and the sectors where the installed sights can be used.

1. Is levelling or a gimbal provided, and does it move without interference through its documented working range? measurement
2. Which bearing sectors are blocked by vessel structures or inaccessible observer positions? measurement
3. When should the observer relocate or defer a sight because of vessel motion or obstruction? action

Sighted target

Separate target identification from the measured direction to a particular point on that target.

1. Which identifiable point on the landmark or vessel is being sighted? definition
2. Can the observer align the fitted vanes or optics and read the scale without losing the target? action

Bearing context

Associate each reading with its observing station, time, target and declared reference.

1. What bearing was read, at what time, from which station and in which reference frame? measurement
2. Did vessel heading or target alignment change between the sight and any supporting heading observation? measurement
3. What additional observations are needed before this bearing can support a position fix or motion assessment? boundary

Bearing quality

Evaluate alignment bias, sighting repeatability and reference uncertainty without inventing a universal tolerance.

1. What spread is observed when the same reference target is sighted repeatedly under controlled conditions? measurement
2. Which uncertainty contributions arise from zero alignment, sight alignment, reading and any external heading? measurement
3. What documented acceptance criterion applies to the intended bearing task? provenance

Serviceability decision

Record sight damage, unreadable graduations, binding movement and failure to retain the selected reference as conditions requiring assessment.

1. Are the sights intact, the scale legible and the rotating or clamping parts functioning as documented? measurement
2. Which manufacturer instructions govern cleaning, adjustment, storage and verification after repair? provenance
3. Which defects require withholding bearings until alignment or serviceability is restored? action

Configuration-dependent limits

Verify powered features, specialised sighting provisions and applicable requirements for the actual variant.

1. Does loss of electrical supply affect only illumination or also the angular reference? boundary
2. If solar observations are proposed, what manufacturer-approved sighting equipment and procedure permit them? action
3. Which issuing body, standard or approval document explicitly applies to this pelorus configuration and installation? provenance

Check these first

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these check these first hold for the sense of Pelorus this model covers, and on what evidence? provenance

Kinds and varieties

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these kinds and varieties hold for the sense of Pelorus this model covers, and on what evidence? provenance

Real-world use

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these real-world use hold for the sense of Pelorus this model covers, and on what evidence? provenance

Typical measurements

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these typical measurements hold for the sense of Pelorus this model covers, and on what evidence? provenance

Failure modes and hazards

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these failure modes and hazards hold for the sense of Pelorus this model covers, and on what evidence? provenance

Neighbouring kinds and how to tell them apart

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these neighbouring kinds and how to tell them apart hold for the sense of Pelorus this model covers, and on what evidence? provenance