Aerial survey line planning — spacing between parallel flight lines on map An area 30 km wide is to be covered by 16 parallel flight lines run perpendicular to the width. What will be the spacing between adjacent flight lines as measured on a photographic map of scale 1:50,000 (assume first and last lines lie along the two edges so spacing = total width/(16 − 1))?

Introduction / Context:
Flight line spacing determines overlap/sidelap and coverage uniformity when planning aerial photography. Converting ground distances to map distances requires careful use of the representative fraction (RF) of the map scale.

Given Data / Assumptions:

• Total coverage width perpendicular to flight lines = 30 km.
• Number of flight lines = 16.
• First and last flight lines coincide with the two edges, so spacing = width/(n − 1).
• Map scale = 1:50,000.

Concept / Approach:
Compute ground spacing between adjacent lines, then convert to map distance using the scale RF. For n lines spanning a fixed width, there are (n − 1) equal intervals between edges.

Step-by-Step Solution:

Verification / Alternative check:
Reverse check: 4 cm on map at 1:50,000 represents 4 * 50,000 cm = 200,000 cm = 2 km on ground, consistent with the computation.

Why Other Options Are Wrong:

• 1 cm, 2 cm, 3 cm, 5 cm correspond to ground spacings of 0.5, 1, 1.5, and 2.5 km respectively at this scale, none of which match 2 km.

Common Pitfalls:
Using n instead of (n − 1) intervals; unit conversion errors (km → m → cm); misreading the map scale RF.

Final Answer:
4 cm