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How to Find the Distance Between Longitude Points

A satellite navigation system isn't the only way to find the distance between two points. Another way is to use latitude and longitude which are measurements used to show how locations are defined on the earth's surface. Latitude is expressed as degrees north and south, longitude as degrees east and west relative to the Greenwich Meridian. Because the earth is spherical longitudinal lines differ in length depending on the latitude; for example at the equator they are much wider than at the poles where the lines disappear. To find the distance between longitude points you will need to use the latitude and geometrical and trigonometric calculations.

Instructions

- 1
  Calculate the approximate distance in miles: sqrt(x * x + y * y) using latitude and longitude values in degrees for example x = 69.1 * (lat2 - lat1) and y = 53.0 * (lon2 - lon1).
- 2
  Add the cosine: where x = 69.1 * (lat2 - lat1) and y = 69.1 * (lon2 - lon1) * cos(lat1/57.3); this will increase the accuracy of the measurement.
- 3
  Use the great circle distance formula to get further accuracy. To do this you will need to use spherical geometry and about 15 digits of floating point mathematical accuracy, also known as double-precision, and will have to use a software application to do the calculation. For this formula you will need to convert the latitude and longitude values from decimals to radians. You can do this by dividing the latitude and longitude values by 180/pi or approximately 57.29577951. The radius of the Earth is assumed to be 3,963 miles.