ECDIS

Question 1

Explain safety contour and safety depth
How is it displayed on the ENC?

Answer 1

Safety Depth - Normally the ships draft + squat

Safety contour - The division between safe and unsafe water, calculated as follows:
Ship’s draft + Squat + UKC - Height of Tide

Question 2

What alarms are triggered by the safety contour

Answer 2

Mandatory Nautical alarm on ECDIS during route planning and monitoring.

Question 3

2 types of electronic charts

Answer 3

Electronic Navigation Charts (ENC) - Digital vector chart made up of multiple layers of information

Raster Navigational Charts (RNC) - Direct digital reproduction of paper chart produced by scanning

Question 4

List 3 items that must be interfaced with ECDIS

Answer 4

Heading (Gyro compass)
Position (GPS)
Speed (Log)

Question 5

Explain term “approved” with reference to electronic navigation charts

Answer 5

Must conform to IMO requirements

Question 6

Describe methods used in creation of a Raster and a Vectorised electronic chart

Answer 6

Raster chart - direct digital reproduction of paper chart reproduced by scanning.

Vectorised chart - Digital chart made up by digitally vectorising multiple layers of information .

Question 7

State 5 operational advantages of using Vector rather than Raster charts

Answer 7

Display can be customized
Possible to zoom without distorting data
Charted objects can be interrogated
Chart data may be shared with other equipment
Less memory required to save data

Question 8

Outline the main dangers when using a chart plotter with a non-approved electronic chart display.

Answer 8

Electronic chart systems are other forms of digital charts and displays which do not meet the IMO requirements, there are no official performance standards.
Can not be used as primary means of navigation.