Published for Free Biology and Maths Tuitions.

1. EARTH GEOMETRY
Locating Places on the
Earth
Two places on the same
longitude but different
latitudes.
Both south of equator?
 If yes, subtract the
latitudes, to find
difference.
Both north of equator?
 If yes, subtract the
latitudes to find the
difference.
One south of equator &
another north?
 If yes, add the
latitudes

2. Two places on the same
latitude but different
longitudes.
Both east of Greenwich?
 If yes, subtract
longitudes
Both west of Greenwich?
 If yes, subtract
longitudes
One east & another west?
 If yes, add longitudes
Distance Along Places
The circle of latitude
∅° 𝑁 𝑜𝑟 ∅° 𝑆 has radius 𝑟 =
𝑅𝑐𝑜𝑠∅, where R=radius of
the Earth.
Arc length=
2𝜋𝑟𝜃
360

3. Examples.
1.Given that the radius of the
earth is 6400km, find
(i)The length of the parallel
latitude 30°𝑁
(ii)The shortest distance
along the surface of the
earth from town Q
(30°𝑁,10°𝐸)to town P
(30°𝑁,50°𝑊
Solution
(i)
Given that R=6400km
∅ = 30° 𝑁, ∅ = 30°
Length=2𝜋𝑟
r=Rcos∅
=2×
22
7
× 6400 × 𝑐𝑜𝑠30
=34,839km
(ii)
2𝜋𝑟𝜃
360
=
2×
22
7
×6400×𝑐𝑜𝑠30×60
360
=
5806𝑘𝑚
𝜃 = 10 + 50 = 60°
r=Rcos∅