[R-sig-Geo] Distance between two points

[O'Hanlon, Simon J]

Dear list,
I am using the package geoRglm to do some predictive mapping. There is a function that calculates the distance between observed data points and the prediction locations using a .C call to a function which eventually calculates the length of the hypotenuse between one location and the other given the vertical and horizontal separation distance of those points.

My question is, is this method of distance-finding incompatible with long-lat style coordinates? Should I first transform my data and prediction locations into something where the unit of measurement is in metres rather than decimal degrees?

Many thanks,

Simon