Navigation General · Chart Datums & Projections
The horizontal datum printed on a U.S. chart affects which of the following most directly?
- AThe depth contour intervals shown
- BThe latitude/longitude coordinates of charted features✓ Correct
- CThe compass rose magnetic variation
- DThe range of heights listed for bridges and overhead cables
Explanation
The horizontal datum (e.g., NAD 83 or WGS 84) determines the geographic coordinates assigned to charted features. GPS receivers output positions in WGS 84; if a chart uses a different horizontal datum, a systematic position error can result. Depths and bridge clearances use a vertical datum, not the horizontal datum.
Authority: Bowditch (Pub. 9), Ch. 2
Practice the full Navigation General bank
Free spaced-repetition quizzing across 2190 USCG exam questions — it schedules your reviews so the ones you miss come back until they stick.
Related Navigation General questions
- Chart Datums & Projections
On a Mercator chart, which of the following statements is TRUE?
- Chart Datums & Projections
A gnomonic chart is primarily used for which purpose?
- Chart Datums & Projections
Soundings on most U.S. nautical charts are referenced to which datum?
- Chart Datums & Projections
On a chart with a scale of 1:80,000, how does one nautical mile compare to one nautical mile on a chart with a scale of 1:20,000?
- Chart Datums & Projections
Which statement about chart scale is CORRECT?
- Dead Reckoning
A vessel departs a known position at 0800 on course 090°T at 12 knots. What is the DR position at 1100?