Introduction to Chartwork Flashcards
What are the depths on charts referred as?
What are the depths on charts based on?
What is a contour line?
Contour Lines:
Depths on chart = ‘Chart Datum’ based on Lowest Astronomical Tide ‘LAT’
LAT = Zero depth where green area meets blue area.
Contour Line = Follows set depth. Anywhere on line is same depth. A= 50m
What are drying areas and how are they marked on the chart?
Tidal areas - sea rises and falls depending on position of sun and moon pulling on earths surface. So can cause land to be partially covered by sea as tide rises and uncovered when tide falls.
These areas, known as ‘drying areas’, are coloured green on the chart and are situated between the 0m contour and the buff coloured land area
Name the following degrees on a compass?
- North
- North East
- East
- South East
- South South East
- Due South
- South West
- West
- West North West
- North West
All points relevant to true North. Should always be written as 3 figures.
North - 000°
North East - 045°
East - 90°
South East - 135°
South South East - 157.5°
Due South - 180°
South West - 225°
West - 270°
West North West - 292.5°
North West - 315°
How are the latitude and longitude measurements?
What is the correct format of writing latitude?
Latitude and longitude are read as degrees, minutes, and decimals of minutes.
- Each degree of latitude = 60 nautical miles
- Each minute of latitude = 1 nautical mile
- 1/10th of a minute of latitude = 1 cable
Latitude Scale - Ensure latitude scale isn’t different to what you’re expecting
Format
00°00’.00.
If the latitude is, 5° 1’.1 is 05° 01’.10 followed by “N” for north or “S” for south.
What should the Longitude Position never be used for?
How is it measured and written?
- Should never be used for measuring speed or distance.
- Measured as E/W of Greenwich on 0° and can be up to 180° meeting on international date line
- Easy to use wrong degree. Golden rule - always use degree nearest to Greenwich
Format: Always shown in three figure notation.
5° west of Greenwich would be written thus, 005° 00’.00 W.
Research some symbols
