SOLAS V/22 Bridge Visibility Calculator: Blind Distance

Q: What is the maximum permissible blind sector ahead of the bow under SOLAS?

Under SOLAS V/22.1.1, the view of the sea surface forward of the bow must not be obscured by more than two ship lengths (2 x LOA) or 500 meters, whichever is less, up to 10 degrees on either side.

Q: What is the formula to calculate the blind distance ahead of the stem?

The total distance where the sightline strikes the water is X_sea = (D_obs * H_eye) / (H_eye - H_obs). The net blind distance forward of the stem is S_blind = max(0, X_sea - D_bow).

Q: What observer eye height is legally mandated for SOLAS calculations?

SOLAS Regulation V/22.1.8 mandates an observer eye height of 1800 mm (1.80 meters) above the bridge deck plating at the conning position.

Q: What occurs if deck cargo height exceeds observer eye height (H_obs >= H_eye)?

If deck cargo height equals or exceeds observer eye height, the line of sight points upward into the sky, resulting in total forward obscuration and a critical SOLAS non-compliance.

Q: How does a trim by the stern affect forward visibility?

Trimming by the stern raises the bow and pitches the line of sight upward across the cargo, significantly increasing the blind sector forward of the stem.

SOLAS V/22 Bridge Visibility Calculator

Evaluation of conning position blind sector forward of the bow in compliance with IMO SOLAS V/22

IMO SOLAS V/22.1.1

Standard Vessel Presets

Vessel & Navigation Bridge Geometry

Length Overall (LOA) For IMO limit calculation

Bridge Deck Height above WL (H_deck) At loaded draught

Observer Height of Eye (H_eye) +1.80m per V/22.1.8

Bridge to Bow Distance (D_bow) To forward stem

Typical: 80–90% of LOA

Visibility Obstruction (Deck Cargo / Containers)

Distance from Bridge to Obstruction Edge D_obstacle

Max Obstruction Height above WL H_obstacle

Blind Sector Ahead of Bow

0.0 m

Obscured sea surface distance

IMO Statutory Limit

280.0 m

min(2 × LOA, 500 m)

Visibility Safety Margin

+0.0 m

Reserve to maximum limit

Water Intercept from Bridge

0.0 m

Total sightline ray to sea

IMO Limit Allowance Used: 0% Max Statutory: 100%

Elevation Profile & Sightline Ray (Side View)

Auto-scaled Vector

Bridge / Observer (1.8m)

Obstruction (Cargo)

Sightline Ray

Blind Sector

Waterline (WL)

Regulatory Framework & IMO SOLAS V/22 Guidelines

SOLAS Chapter V, Regulation 22 (Navigation bridge visibility):

Paragraph 1.1: The view of the sea surface from the conning position shall not be obscured by more than two ship lengths, or 500 m, whichever is less, forward of the bow to 10° on either side under all conditions of draught, trim and deck cargo.
Paragraph 1.8: The standard height of eye is defined as 1,800 mm (1.8 m) above the bridge deck level at the conning position.
Geometric Calculation: By similar right triangles, total distance to the sea surface intercept is X_sea = D_obs × H_eye / (H_eye - H_obs). Obscuration forward of the bow: S_blind = max(0, X_sea - D_bow).

Navigation Safety Hub IMO // SOLAS V/22.1.1

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Bridge Navigation Visibility: SOLAS Regulation V/22 Blind Sector Assessment

Maintaining an unobstructed visual lookout from the navigation bridge is a statutory safety mandate under Regulation 22 of SOLAS Chapter V and Rule 5 of the International Regulations for Preventing Collisions at Sea (COLREGs). When loading container tiers on hatch covers, deck timber cargoes, or project equipment, Shipmasters and Chief Officers must verify that forward sea surface obscuration stays well within statutory thresholds. Port State Control (PSC) regimes (Paris MoU, Tokyo MoU, USCG) routinely inspect cargo visibility declarations and detain non-compliant vessels.

The NavLib SOLAS V/22 Bridge Visibility Calculator automates geometric sightline analysis from the conning position. The software resolves the sea surface tangent point, calculates the net obscured blind distance forward of the stem (Blind Distance), verifies the statutory limitation of min(2 x LOA, 500 m), and exports verified compliance declarations for port clearance and cargo stowage files.

Statutory Geometry

SOLAS V/22.1.1 Limits

Automated auditing of forward sea surface obscuration: restricted to no more than two ship lengths (2 x LOA) or 500 m, whichever is less, across 10° either side.

Conning Station

Eye Height & Datum

Strict application of the statutory 1800 mm (1.80 m) observer eye height datum above the wheelhouse deck plating pursuant to SOLAS Regulation V/22.1.8.

Vector Diagram

Dynamic Sightline SVG

Real-time profile rendering with color-coded blind sectors, deck cargo height limits, and isolated A4 portrait printing for official inspection audits.

Frequently Asked Questions: Bridge Visibility & SOLAS V/22 (FAQ)

What is the maximum permissible blind sector ahead of the bow under SOLAS?

Under SOLAS Chapter V, Regulation 22.1.1, the view of the sea surface from the conning position shall not be obscured by more than two ship lengths (2 x LOA) or 500 meters, whichever is less, forward of the bow to 10 degrees on either side under all operational conditions of draught, trim, and deck cargo.

What is the formula to calculate the blind distance ahead of the stem?

The sightline geometry uses similar triangles:
1. Total distance from the bridge conning point to where the line of sight strikes the sea surface:
X_sea = (D_obs * H_eye) / (H_eye - H_obs)
where D_obs is the horizontal distance from the bridge to the forward edge of the obstruction, H_eye is observer eye height above the waterline, and H_obs is obstruction height above the waterline.
2. Blind distance forward of the bow:
S_blind = max(0, X_sea - D_bow)
where D_bow is the horizontal distance from the bridge conning point to the vessel's stem.

What observer eye height is legally mandated for SOLAS calculations?

SOLAS Regulation V/22.1.8 strictly defines the observer's eye height as 1800 mm (1.80 meters) above the bridge deck plating at the conning position.

What occurs if deck cargo height exceeds observer eye height (H_obs >= H_eye)?

If the top of the deck cargo or containers equals or exceeds the height of the observer's eye, the line of sight aims parallel or upward into the sky, creating total forward visual obstruction. This constitutes an immediate critical SOLAS violation. The vessel will be denied departure until container tiers are restowed or water ballast adjusted.

How does a trim by the stern affect forward visibility?

A trim by the stern tilts the ship's longitudinal axis, elevating the bow and lowering the aft deckhouse. This angle pitches the sightline upward over the cargo, substantially expanding the blind sector ahead of the bow. SOLAS V/22 calculations must therefore be conducted for the worst-case departure trim condition.

Regulations: IMO SOLAS V/22.1.1, SOLAS V/22.1.8, COLREGs Rule 5

Inspections: Port State Control (PSC), USCG, Class Cargo Securing Manual

Reporting: Isolated DOM Print (A4 Portrait), LocalStorage Auto-Save