Enter the latitude, declination of the sun, and hour angle into the calculator to determine the subsolar point.
Subsolar Point Formula
The following formula is used to calculate the subsolar point on Earth.
SP = arccos(sin(L) * sin(D) + cos(L) * cos(D) * cos(H))
Variables:
- SP is the subsolar point (degrees)
- L is the latitude of the observer (degrees)
- D is the declination of the Sun (degrees)
- H is the hour angle (degrees)
To calculate the subsolar point, first take the sine of the latitude and multiply it by the sine of the declination. Then, take the cosine of the latitude and multiply it by the cosine of the declination and the cosine of the hour angle. Add these two results together and then take the arccosine of the sum to get the subsolar point.
What is a Subsolar Point?
A subsolar point is the specific location on the Earth’s surface where the sun is perceived to be directly overhead at a particular moment. This point moves across the Earth’s surface as the planet rotates and also changes throughout the year due to the tilt of the Earth’s axis. The subsolar point reaches its most northerly position at the Tropic of Cancer during the June solstice and its most southerly position at the Tropic of Capricorn during the December solstice.
How to Calculate Subsolar Point?
The following steps outline how to calculate the Subsolar Point using the given formula:
- First, determine the latitude of the observer (L) in degrees.
- Next, determine the declination of the Sun (D) in degrees.
- Next, determine the hour angle (H) in degrees.
- Next, substitute the values of L, D, and H into the formula: SP = arccos(sin(L) * sin(D) + cos(L) * cos(D) * cos(H)).
- Finally, calculate the Subsolar Point (SP) in degrees.
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem:
Use the following variables as an example problem to test your knowledge:
Latitude of the observer (L) = 40 degrees
Declination of the Sun (D) = 23 degrees
Hour angle (H) = 60 degrees
