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Answer 1

At the equator, both longitude and latitude measure approximately 60 nautical miles. This converts to 69.046767 statute miles.

Both latitude and longitude degree lengths change with respect to latitude; latitude however changes very minimally between the equator and the poles, the distance only changes by about 75 meters between 0 degrees (the equator) where the degree length is 110574 meters, and 90 degrees (the north pole) the degree length of latitude is 111694 meters (note: miles = meters/1609.344)

Longitude however changes quite a lot from the equator to the poles, at 90 degrees the degree length of longitude is 0, where as at the equator it is 111320m.

There are a number of ways of finding the degree length, for close enough approximations it is usually said that the degree length of latitude does not change, lets say it's=111132m (it's that around 45 degrees of latitude), and degree length of longitude is then computed as:

L - latitude in radians

Longitude = 111132*cos(L)

(note: here that since its a trig function you have to convert degrees to radians, which can be done with radians = degrees*pi/180)

A much more close approximations for arcdegree lengths, based on an ellipsoid earth are:

(Radii based on WGS-84 ellipsoid, used by all current GPS devices)

E - equatorial radius - 6378137

P - polar radius - 6356752.314

L = latitude in radians

Latitude = (pi/180)*((PE)2/((E*cos(L))2+(P*sin(L))2)3/2)

Longitude = (pi/180)*cos(L)*(P2/((E*cos(L))2+(P*sin(L))2)1/2)