How are distances computed, in general? (That is, as the crow flies or straight line distance)

• A. Map bar scale
• B. Legend
• C. Compass rose
• D. Grid lines

Answer: (A)

Distances on a map are determined by the scale. To get the straight-line distance between two points, you measure the direct line on the map and then use the scale to convert that map distance into real-world units. The scale bar is a handy, direct readout showing how far on the ground corresponds to a given length on the map, so it’s the tool you use for the actual conversion. For example, if the scale bar indicates 1 cm on the map equals 10 km in the real world, and the measured line between the points is 3 cm, the real straight-line distance is 30 km. The other features serve different purposes: the legend explains symbols, the compass rose indicates direction, and grid lines help locate positions; they don’t provide the conversion from map distance to real distance.