Magnetic Compass Deviation Card

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NAVLIB - Magnetic Compass Deviation Card & S-Curve Generator

Magnetic Compass Deviation Card & S-Curve

NAVLIB Marine Navigation Suite • Airy / Poincaré Harmonic Analysis & S-Curve Plotter

Vessel Particulars & Observation Conditions

Particulars

Observed Deviation (8 Cardinal Headings)

Observed Data
Course (CC) Deviation (δ) Magnetic (MC)

Deviation Coefficients (Airy / Poincaré)

Harmonics
A
+0.0°
Constant A
B
+0.0°
Fore-and-Aft B
C
+0.0°
Athwartships C
D
+0.0°
Quadrantal D
E
+0.0°
Quadrantal E
δ(θ) = A + B·sin(θ) + C·cos(θ) + D·sin(2θ) + E·cos(2θ) (θ = CC)

Real-Time Navigation Calculator

Live Calculation
+0.0°
000.0°
000.0°
Formulas: MC = CC + δ, TC = MC + Var (where Var = 3.5° W)

Deviation Graph (Admiralty S-Curve)

Scale: ±10°
Vertical Heading Scale (000° ➔ 360°)

Working Deviation Table

Course (CC) Deviation (δ) Magnetic Course (MC) True Course (TC)

Magnetic Compass Deviation Card & S-Curve Table Generator

The NAVLIB Magnetic Compass Deviation Card & Curve Generator is a specialized maritime application engineered for Master Mariners, Navigation Officers (OOW), and Certified Compass Adjusters[cite: 1, 3]. It simplifies residual deviation analysis, computes harmonic coefficients (Airy / Poincaré formulations), and plots a professional vertical S-Curve in full compliance with SOLAS Chapter V (Regulation 19) and IMO Resolution A.382(X).

δ(θ) = A + B·sin(θ) + C·cos(θ) + D·sin(2θ) + E·cos(2θ)

By entering observed deviations across 8 principal headings (000°, 045°, 090°, 135°, 180°, 225°, 270°, 315°), the algorithm computes the continuous magnetic deviation profile across the entire 360° compass rose at 15° intervals.

Key Features & Operational Highlights

📈 Standard Vertical S-Curve Layout Plotted in the recognized Admiralty Form NP159 design: vertical heading axis from 000° (top) to 360° (bottom) with West (-) and East (+) horizontal scale.
📐 Harmonic Coefficients A, B, C, D, E Instant calculation of constant, semicircular, and quadrantal magnetic parameters of the vessel's hull and cargo influence.
💾 JSON Data Session Export & Import Save vessel parameters into a structured JSON file formatted as DeviationCard_[ShipName]_[Date].json for seamless reloading on any device.
🖨️ A4 Print & PDF Certificate Mode Dedicated print stylesheet producing a clean bridge certificate with ship particulars, deviation table, S-Curve grid, and signature lines for Master and Adjuster.

Frequently Asked Questions (FAQ)

When must a magnetic compass deviation card be renewed?

In accordance with IMO standards: after extensive shipyard repairs, carriage of magnetic cargo (e.g., steel, iron ore), lightning strikes, structural alterations, or whenever observed deviations exceed ±3°–5° on any heading.

How is Magnetic Course (MC) derived from Compass Course (CC)?

Apply the standard marine rule: Magnetic Course (MC) = Compass Course (CC) + Deviation (δ). East deviations are positive (+), while West deviations are negative (-).

Disclaimer: This application is intended for operational and educational assistance. The Officer of the Watch remains responsible for cross-checking compass errors with the Compass Error Log Book and celestial observations.

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