Regents Prep: Earth Science: Mapping: Latitude & Longitude

Latitude and Longitude
This is the coordinate system that we use on Earth. It is measured in angular units: degrees, minutes, and seconds. There are 60 minutes in a degree, and 60 seconds in a minute.

Latitude

 Latitude is the angular distance north or south of the equator. The equator is the middle location on the Earth's surface, and is located halfway between the North and South poles. If a line is drawn from any point on the Earth's surface to the center of the Earth, the angle that line makes with the equator is that location's latitude. The diagram on the right shows the equator (highlighted in red), as well as other lines of latitude and longitude.

Measuring Latitude
The North Star (Polaris) is located directly above the North Pole. This means that the altitude of the North Star in the sky is equal to the latitude of the person observing it. If you are at 90 degrees North latitude (the North Pole), Polaris will be 90 degrees above the horizon (directly overhead).

As shown in the example to the right, this method will work for any location in the northern hemisphere. The girl in the diagram must be at 42 degrees North latitude.

Longitude

 Longitude is the angular distance east or west of the Prime Meridian. The Prime Meridian is designated as 0 degrees longitude, and passes through Greenwich, England. The diagram on the right shows the Prime Meridian (highlighted in red), as well as other lines of latitude and longitude.

Measuring Longitude
Solar noon is defined as being the time at which the sun reaches its highest point in the sky. Since the Earth rotates on its axis at a rate of 3600 per day, it rotates at a rate of 150 per hour (3600 divided by 24 hours). This means that the occurrence of solar noon will move from east to west at a rate of 150 per hour. Longitude can be calculated, if when solar noon occurs, the observer knows what time it is at the Prime Meridian. By determining how many hours difference there is between you and the Prime Meridian, you can calculate how many degrees of longitude away you are (using the formula of 150 per hour).

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