What are Altitude and Azimuth? (Intermediate)

I have just received a GeoClock program that runs on my PC. It graphically shows the position of the sun and gives figures for Azimuth and Elevation. I'm confused about what Azimuth and Elevation mean in reference to plotting the sun's course across the sky. Does one represent the position from North to South and the other represent the position East to West? This is very basic, but its been so long that I have used this information that I've lost track. Thanks for your help!

Azimuth represents the cardinal direction in which the object (in this case, the sun) can be found. It varies between 0 and 360 degrees. 0 degrees would be north, 90 east, 180 south, and 270 west.

Once you know in which direction the object is located, you need to know how high in the sky to look for it. That's where Altitude comes in. Altitude ranges from 0 to 90 degrees, and measures the angle between the horizon, you, and the object. An object with 0 degrees altitude is right on the horizon, while an object at 90 degrees altitude is directly overhead. If you stretch out your arm and make a fist, then your fist covers about 10 degrees on your field of vision, so if the sun is at 40 degrees altitude, it is about 4 outstretched fists above the horizon.

Occasionally, you will see altitudes less than zero, e.g. "At 9:30 PM, the sun will be at -20 degrees altitude." In this case, the sun would be 20 degrees below the horizon, you would be unable to see it, and it would be night time.

This page was last updated June 28, 2015.

About the Author

Dave Kornreich

Dave was the founder of Ask an Astronomer. He got his PhD from Cornell in 2001 and is now an assistant professor in the Department of Physics and Physical Science at Humboldt State University in California. There he runs his own version of Ask the Astronomer. He also helps us out with the odd cosmology question.

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