Earth geometry — variation of one degree of longitude and latitude with latitude Which statement correctly describes how the ground distance represented by one degree changes from equator to poles?
-
AOne degree of longitude has its greatest ground distance at the equator
-
BOne degree of longitude has its greatest ground distance at the poles
-
COne degree of longitude has the same ground distance everywhere
-
DOne degree of latitude decreases from the equator to the poles
-
EOne degree of latitude has the greatest ground distance at the poles
Answer
Correct Answer: One degree of longitude has its greatest ground distance at the equator
Explanation
Introduction / Context:Surveying and cartography rely on how angular measures map to ground distances on a spherical or spheroidal Earth. Understanding this helps with scale and convergence effects.
Given Data / Assumptions:
- Earth approximated as a sphere/spheroid.
- “Value” refers to linear ground distance corresponding to one degree.
Concept / Approach:
Lines of longitude converge at the poles and are widest apart at the equator. Therefore, the ground distance per degree of longitude is maximum at the equator and diminishes to zero at the poles. By contrast, spacing of parallels (latitude) is nearly constant, so one degree of latitude is approximately the same distance everywhere (minor variation with ellipsoid flattening).
Step-by-Step Solution:
Longitude spacing ∝ cos(latitude) → maximum at 0°, zero at 90°.Latitude degree length ≈ constant (about 111 km).Hence option (a) is correct.Verification / Alternative check:
Meridian arc tables show ~110.6–111.7 km per degree latitude; longitude is ~111.32 km at the equator and 0 at the poles.
Why Other Options Are Wrong:
- (b) and (c): contradict convergence of meridians.
- (d) and (e): misstate latitude degree behavior (nearly constant).
Common Pitfalls:
- Confusing distances along meridians versus along parallels.
Final Answer:
One degree of longitude has its greatest ground distance at the equator.