Charts and Chart Projections
Why Projections Exist
A chart is a flat representation of a curved surface, so every projection distorts something: shape, area, scale or direction. A candidate must state which properties are preserved and the navigational consequence.
Mercator
A normal Mercator is conformal: angles and small shapes are correct, and a rhumb line plots as a straight line. Scale expands with latitude by sec(latitude), so the same physical distance occupies more chart space at high latitude. Great circles plot as curves concave to the pole. It is the standard plotting chart for dead reckoning and radio bearings.
Transverse Mercator and Lambert Conformal Conic
A transverse Mercator has its cylinder along a meridian; it is conformal and used for charts where north–south extent dominates. A Lambert conformal conic is conformal, has straight meridians and concentric arcs for parallels, and plots great circles as almost straight lines; it suits mid-latitude charts such as those of Brunei's region.
Other Types
Polar stereographic is used near the poles; the gnomonic is the only projection on which all great circles are straight lines but it is not conformal. Oblique and grid charts appear in high-latitude operations.
Traps
Watch for questions mixing conformality with great-circle straightness, and for scale questions: on a Mercator, a measured distance must use the scale at the latitude of the measurement.
Rule of Thumb
Mnemonic: Mercator = rhumb lines straight; Gnomonic = great circles straight; Lambert conformal conic = both nearly straight at mid-latitudes.