Delta Fares

How does a degree of longitude vary in size?

Is there a nice formula that will tell me how a degree (expressed as radians) of longitude varies in size? E.g. at the equator 1 mile is approximately 0.014467 radians. I am looking for a nice formula that will tell me what this delta radians for 1 mile is at 45 degrees, 47 degrees, etc. Your help is much appreciated.

Public Comments

1. One minute of latitude is 1 nautical mile. One minute of longitude is cos( | latitude | ) nautical miles. where | x | means absolute value of x. ie make it +ve whatever the sign of it.
2. 1 mile is approximately 0.014467 degrees at the equator, not radians. For other latitudes, simply multiply by the cosine of the latitude. This should be pretty accurate, but not exact, since the Earth is an oblate spheroid rather than a sphere.
3. Your use of prepositions is really unfortunate, that makes you say 'no I didn't mean this, I meant that'. A degree of longitude (I interpret it as A degree on longitude line) does not vary. 1 degree= 60nautical miles= 0.0174533 radians {@equator in ur words} 1 naut. mile = 0.29 milliradians = (20/23) st. miles 1 st.mile = 0.253 milliradians (= 0d 52' 10.43") A degree on a latitude (between two longitude lines differing in 1 degree) is a function of latitude (a) 60*cos a naut.miles However, don't interpret saying that the length of a naut.mile varies with latitude. It remains the same at 6080 feet.