E nav

The skipper of a 7m RIB plans to do a coastal passage using a hand held GPS and a paper chart inside a waterproof cover. His estimated cruising speed is 15Kts.

GPS is generally very reliable and accurate. Give 2 possible causes of inaccurate positions.

• Option 1: Damage to the aerial

• Option 2: Power failure

• Option 3: Difficulties with the radar system

• Option 4: Unpredictable triangulations

Identify some simple precautions you can take in case of GPS failure.

• Option 1: Regularly call home and ask a friend to write down your current position

• Option 2: Regularly record the current position in the logbook

• Option 3: Ensure the crew are in an effective watch pattern

• Option 4: Plot the current position on the chart at regular intervals

GNSS receivers usually have functions to allow you to view the number of satellites in use and to view the value of Horizontal Dilution of Precision (HDOP).  Which factors would give you more confidence in the precision of the location?

• Option 1: A HDOP of below 2 indicates an excellent precision

• Option 2: A HDOP over 10 indicates an excellent precision

• Option 3: 2 or more satellites will give a good location

• Option 4: 4 or more satellites will give a good location

A waypoint is a reference point used in navigation, often as part of a route. Their latitude and longitude can be measured from the chart or found in almanacs and other books.

The GNSS will display the direction and distance to the waypoint, but does a basic GPS make an allowance for the tidal stream when giving the direction?

• YES

• NO

What does the abbreviation XTE stand for?

• Option 1: Calculation Track Error

• Option 2: Calculation Transmission Error

• Option 3: Cross Trail Error

• Option 4: Cross Track Error

If a waypoint is chosen in an unsafe area or if the route crosses a hazard, will a basic GPS give a warning or navigate round the danger?

• yes

• no

What else could you do to help verify your position?

• Option 1: Check that the GPS positon recorded was correctly entered in the log

• Option 2: Check with the Coastguard on the VHF

• Option 3: Plot a fix

• Option 4: Plot an estimated position

A leisure chart plotter usually displays a warning when it is switched on. Is an electronic chart an official navigational chart?

• yes

• no

Snapshot B shows the settings function on a chart plotter that allows the user to customise aspects of its operation. The chart plotter in this illustration is being configured for use with the paper Training Chart 3.

Identify any changes to the units settings that would better match the chart plotter to the paper chart.

• Option 1: The geodetic datum should be set to WGS 66

• Option 2: Depths should be set to metres instead of feet

• Option 3: Distances should be set to nautical miles instead of kilometres

• 
  Option 4: Speed should be set to knots

Suggest two advantages to setting the variation to 'automatic'?

• Option 1: There is no requirement to update the value each year

• Option 2: There is no requirement to update the value when the vessel travels to different locations

• Option 3: There is no requirement to update the value each time the plotter is turned on

• Option 4: There are no advantages