IFMP Authorized Surveying Officers Certification flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Chart datum

The low-water reference surface to which depths on a nautical chart are reduced, chosen so that actual water level is usually above the charted depth.

True bearing

A direction measured clockwise from true north through 360 degrees, independent of magnetic variation and compass deviation.

Dead reckoning

A position advanced from a known fix using course and speed through the water, without using external position observations.

Line of position

A locus of points where a navigator measures a constant value, such as a bearing or range; intersecting lines produce a fix.

Territorial sea

The belt of sea adjacent to a coastal state's baseline, extending up to 12 nautical miles, over which the state has sovereignty subject to innocent passage.

Exclusive economic zone

A zone extending up to 200 nautical miles from the baseline in which the coastal state has sovereign rights over resources while other states retain navigation freedoms.

Equidistance line

A boundary line every point of which is equally distant from the nearest points of the baselines of two states, used as the default delimitation method.

Normal baseline

The low-water line along the coast as marked on large-scale charts officially recognized by the coastal state, from which maritime zones are measured.

Survey order

A classification setting the maximum allowable horizontal and vertical uncertainty for a survey, chosen to match the intended use of the waters.

Total vertical uncertainty

The combined uncertainty in a depth measurement, often modeled as the square root of a squared plus the square of b times depth.

Geoid

The equipotential surface of the Earth's gravity field approximating mean sea level, used to convert ellipsoidal heights to orthometric heights.

Dilution of precision

A measure of satellite geometry quality; a low value indicates strong geometry and better expected positioning accuracy.

Line spacing

The distance between adjacent survey lines, commonly set as a multiple of water depth to ensure adequate coverage and overlap.

Sound speed profile

A measurement of sound velocity versus depth in the water column, used to correct echo sounder depths for refraction and variation.

Multibeam echosounder

An acoustic system that measures depth across a wide swath perpendicular to the vessel track, producing dense bathymetric coverage.

Side-scan sonar

An acoustic imaging system that shows seabed texture and contacts to the sides of the towfish but does not provide reliable depth.

Tidal reduction

The correction applied to measured soundings to reduce them to chart datum using observed or predicted water levels at the time of survey.

Patch test

A calibration procedure using carefully chosen survey lines over suitable terrain to estimate transducer offsets, latency, and heading, pitch, and roll biases.

Lever arm

The measured offset between a sensor and a reference point, such as antenna to transducer, which must be applied to correct positions.

Bar check

A calibration check in which the echo sounder is compared against a target lowered to known depths to detect offset or scale error.

Motion sensor

An inertial unit measuring vessel roll, pitch, and heave, whose alignment and offset must be calibrated to avoid depth error.

Shoal-biased selection

A data thinning rule that keeps the shallowest significant sounding in each area, preserving safety while reducing data volume.

Cross-check line

A survey line run across the main survey direction to test consistency and reveal systematic errors in depth or position.

Total propagated uncertainty

A combined uncertainty estimate accounting for measurement, positioning, motion, and sound speed errors, used to judge compliance with survey order.

Outlier

A sounding or position that deviates markedly from surrounding data and must be investigated before it is accepted or rejected.

Shoal-biased rounding

A charting rule that rounds depths toward the shallower value so displayed depths do not overstate the water available to mariners.

Survey report

A document stating the survey order, datums, equipment, calibration results, coverage, and limitations of the delivered survey.

Metadata

Descriptive information such as coordinate reference system, vertical datum, units, resolution, and processing history that makes a dataset usable.

Risk assessment

A documented evaluation of hazards and the controls applied to each, completed before survey operations begin.

Muster point

A designated assembly location on a vessel used during emergencies such as fire, man overboard, or abandon ship.

Scope of certification

The range of survey activities a certified officer is authorized to perform; work outside that range is a compliance failure.

Hazard reporting

The professional duty to notify the relevant maritime authority promptly of a discovered danger to navigation, even when not contractually required.