FAQ - Reading & Interpreting Charts
How do I read depth soundings/contours?
Numbers are depth at LAT; contours connect points of equal depth.
Meaning of symbols for reefs, rocks, wrecks?
Crosses/dotted circles denote hazards; "VK" means wreck; "R" means reef.
How to interpret leads, transits, and sector lights?
Follow the line of the "Leading Lights"; stay within the white light sector.
What is chart datum?
The vertical reference (usually LAT) for all charted depths.
How to convert true to magnetic bearings?
Add/subtract the "Variation" found in the chart's compass rose.
What does LAT mean?
Lowest Astronomical Tide; the lowest level the tide can be expected to fall.
How do I use tidal stream arrows?
Arrows show direction; the numbers (e.g., 2,4kn) show spring/neap rates.
How to plan under-keel clearance?
(Charted Depth + Tide) - Vessel Draft = Clearance.