A planetary coordinate system is a way of naming points on the surface of a planet or moon. Every point on the surface of a planet has a unique name so that people can find it easily. To name these points, we use a coordinate system which uses two numbers: one for latitude and one for longitude.
Latitude measures how far north or south a point is from the equator of the planet. The equator is an imaginary line that goes all the way around the middle of a planet. Longitude measures how far east or west a point is from the Prime Meridian, which is a line that starts at the North Pole and ends at the South Pole.
With these two numbers, we can give a unique name to any point on the surface of a planet. The latitude and longitude of a point are usually written in degrees and minutes. For example, a point on the surface of the Earth might be 37 degrees, 27 minutes North and 122 degrees, 54 minutes West.
By using the planetary coordinate system, we can make sure we can find any point on the surface of a planet or moon.