Maritime and Marine Marine Navigation and Charting 2

Question 1

What is the minimum number of GPS satellites needed to compute a two-dimensional position fix (latitude and longitude only)?

Accepted Answer

3

Answer

At least three satellites are required for a 2D position fix (latitude and longitude), while a fourth satellite is needed to also solve for altitude in a 3D fix.

Question 2

What does 'Differential GPS' (DGPS) primarily improve?

Accepted Answer

The accuracy of GPS position fixes by applying land-based correction signals

Answer

DGPS uses land-based reference stations to broadcast real-time corrections to GPS signals, significantly improving position accuracy, especially in coastal waters.

Question 3

What does the acronym 'ECDIS' stand for?

Accepted Answer

Electronic Chart Display and Information System

Answer

ECDIS stands for Electronic Chart Display and Information System, a computer-based navigation system that integrates vessel GPS position with electronic navigational charts (ENCs).

Question 4

What does 'COG' indicate on a GPS or chart plotter display?

Accepted Answer

Course Over Ground

Answer

COG (Course Over Ground) is the actual direction the vessel is tracking over the earth's surface, incorporating the effects of current, leeway, and wind on the vessel's movement.

Question 5

When using a GPS chart plotter near hazards, what is the most critical consideration to avoid position errors?

Accepted Answer

Verifying the GPS datum matches the chart datum

Answer

A mismatch between the GPS datum and the chart datum can cause significant position errors, potentially placing a vessel dangerously close to shoals or rocks.

Maritime and Marine Practice Test

Maritime and Marine Practice Test

Maritime and Marine Marine Navigation and Charting 2