Hydrographic Survey Standards & Quality Control Flashcards

Which international standard provides the specifications for the content and format of digital hydrographic data exchange, including S-57 and S-100 product families?

Answer: IHO S-57 and the S-100 Universal Hydrographic Data Model

IHO S-57 is the established ENC data standard, and S-100 is its successor framework defining the universal hydrographic data model for modern chart products.

A quality control review finds that sounding density in a completed MBES survey is below the minimum required in a critical navigation area. What is the most appropriate corrective action?

Answer: Return to the area and infill the data gaps with additional survey lines

Insufficient sounding density in critical areas must be corrected by returning to collect additional data, as interpolation and alternative sources do not meet survey specification requirements.

In the CUBE (Combined Uncertainty and Bathymetric Estimator) algorithm, what is the primary advantage over simple nearest-neighbor gridding?

Answer: CUBE weights soundings by their individual uncertainty and detects multiple depth hypotheses in ambiguous areas

CUBE uses per-sounding uncertainty weights to compute statistically optimal depth estimates and can identify areas where two distinct depth hypotheses exist, flagging them for review.

A hydrographic survey is conducted in an area where the tidal range exceeds 4 m. Which water level collection strategy provides the most accurate tidal correction?

Answer: Deploying temporary tide gauges within the survey area supplemented by verified water level zoning

In high-tidal-range areas, temporary gauges deployed within the survey zone provide the most accurate water level corrections, supplemented by zoning from nearby control gauges.

What is the definition of 'least depth' in the context of hydrographic feature detection and charting?

Answer: The shallowest depth measured over a feature, used to characterize the hazard to navigation

Least depth is the shallowest depth detected over a feature and is the critical value used to assess and chart the navigation hazard.

Under IHO S-44 standards, what is the maximum allowable TVU (at 95% confidence) for Order 2 surveys at a depth of 50 m, using parameters a=1.0 m and b=0.023?

Answer: Approximately 1.32 m

TVU = √(a² + (b×d)²) = √(1.0² + (0.023×50)²) = √(1 + 1.3225) ≈ √2.3225 ≈ 1.32 m at 95% confidence for Order 2.

Which documentation is required in a NOAA Hydrographic Survey Project Instructions (HSPI) to define the geographic scope and priority areas of a survey project?

Answer: The survey limits diagram and priority area polygons with associated order requirements

HSPI must include survey limits diagrams and priority area polygons specifying the geographic scope and the applicable IHO order for each area.