Charts Flashcards
What would you find on a routing chart
- Wind rose with; prevailing wind for time of year of chart in Beaufort number, number of obsevations, percentage of variable winds, percentage of calms,
- ocean currents
- mean iceberg limit
- great circle shipping route distances
- load line zones
- tropical storm tracks
- percentage of Beaufort wind scale seven or greater
- dew point temp
- mean sea temp
- mean air pressure
- mean air temp
- fog
- low vis
Publication for chart symbols
NP 5011,
What is a rhumb line
Line which cuts all the meridians at the same angle
What is a great circle route
It is the shortest distance between two points on the earths sphere,.
The shortest distance between two points on a globe is the circumference of the circle that joins them where the centre of the circle is the same as the centre of the sphere.
The great circle route extended to itself will always cut a sphere exactly in half.
Equator is a great circle and all meridians.
What is a Mercator projection
It is a projection where a rhumb line cuts all the meridians at the same angle.
How would You draw and transfer a route from a Gnomonic chart to a mercator chart.
Draw the route on to the genomic chart. (Straight line from point A to point B)
Add a waypoint every 15deg. Tackle the co-ordinates for the waypoints and plot them onto a ,reactor projection. It will appear as an ARC.
How to check Chartrs up to date.
Current Cumulative list of notice’s to mariners. (Release January and July).
Find chart number In list.
Check Chart edition is latest
Check bottom left of chart for list of applied NTM’s (year, Week, correction number)
Check Corrections match Cumulative list.
If all match then Charts is up to date until Cumulative notice.
Next need to check each weekly NTM up until current date. By looking in index of effected charts.
Enter chart corrections onto bottom corner of chart and then into Np133A Paper chart maintenance record.
Datums on the chart for measurement of depth, drying height and clearing heights
Depth - Chart datum (LAT)
Drying height - Chart datum (LAT)
All other heights - Above MHWS
Bridge height (Vertical Clearance/Air draft) - Above HAT
