Latitude

Latitude is a measurement that specifies the north-south position of a point in the geographic coordinate system. It is measured in degrees (°) and ranges from 0° to 90° north or 90° south, spanning a total of 180°.

You can think of the geographic coordinate system as dividing the earth up into a grid, with latitude telling you the north-south position, and longitude telling you the east-west position.

If you are familiar with the coordinate plane, the concept of latitude and longitude are similar to the x and y position on the coordinate plane, except that the geographic coordinate system lies in 3D, as part of a sphere, rather than in 2D, on a plane.

In the geographic coordinate system, the equator divides the Earth into its northern and southern hemispheres, similar to the x-axis in the coordinate plane.

Expressing latitude

The primary unit of latitude is degrees, but it can be further broken up into minutes (') and seconds ("):

1° = 60' = 3600"

This allows us to be more precise, since not all positions that we want to reference will align with a whole degree since each degree of latitude is approximately 69 miles on earth. 42°3'27" N is one example of how we can write a latitude. It is read as "42 degrees, 3 minutes, 27 seconds north." We can also write the 3'27" portion of the latitude in decimals. To do this, we convert the minutes and seconds into their fractions of a degree:

When writing latitude and longitude, we always write the latitude first. So, if giving the coordinates of Houston, TX, we could write it as:

Degrees minutes seconds: 29°45'47.808" N 95°21'47.772" W

Decimal degrees: 29.76328° N 95.36327° W

These aren't the only ways latitude and longitude can be written. There are a number of other ways. For example, instead of specifying a direction like N for north, or W for west, we could use positive and negative numbers. Positive latitude indicates north and negative latitude indicates south. Positive longitude indicates east and negative longitude indicates west.