Map Projections and Distortion Questions and Answers

Answer: A

Correct answer: a great circle

The shortest path on a sphere is an arc of the great circle through the two points - the circle whose plane passes through the centre of the Earth. A rhumb line crosses every meridian at the same angle and is longer, sometimes very much longer at high latitudes. Only on the gnomonic projection does a great circle appear as a straight line, which is why gnomonic charts are used to plan a route and Mercator charts to steer it.

Answer: B

Bearings measured from the centre of an azimuthal projection are correct to anywhere on the map, which is what makes it useful for radio, aviation and polar work. Other properties depend on which azimuthal variant is used.

Answer: C

How the graticule appears is one of the clearest signs of which projection is in use, since the spacing and curvature of the lines differ between them. It is distinct from a rectangular grid such as UTM laid over the map.

Answer: D

Wrapping a cylinder around the Equator makes the meridians vertical and evenly spaced, which is why such maps are rectangular. On the globe they converge at the poles, and that convergence is exactly what the projection has removed.

Answer: A

Correct answer: straight lines radiating from a point

Unrolling the cone gives a fan. The meridians become straight lines radiating from the apex, spaced at angles proportional to the differences in longitude, and the parallels become concentric arcs centred on the same apex. That is the signature of a conic projection in normal aspect, and it explains why such maps are usually cropped to a band of latitude.

Answer: B

Conformality is bought with area distortion that grows with latitude, so high-latitude countries appear far larger than they are. Local shape is exactly what the projection does keep, which is why the criticism has to be aimed at area.

Answer: C

Correct answer: Lambert Conformal Conic and Albers Equal Area

These two are the conformal and equal-area conics, constructed on the same cone with the same standard parallels and differing only in how the parallels are spaced along the radii. They are the standard pair for a mid-latitude region, and which to use depends entirely on whether angles or areas matter for the map in hand.

Answer: D

Correct answer: near the standard lines of the projection

The standard line or lines are where the projection surface meets the globe, so the scale there is true and the distortion is nil. It grows with distance from them, which is why a projection is chosen and centred so that its standard lines fall through the region being mapped. Corners and edges have no special status except that they are usually furthest from those lines.

Answer: A

Correct answer: they use different projections

Every projection distorts, and different projections distort differently, so the same coastline drawn on two of them will differ in shape, in relative area and in the curvature of its graticule. Nothing about the paper size, the printing date or the number of labels alters the geometry - only the projection does.