I need some good pointers to how could I derive arbitrary small circle equation in spherical coordinats (by hand or computer-aided), that is, LONG(t), LAT(t) or something like that. Also, any approximate equations? How bad they are? Please do not advice switching to cartesian, this is exactly what I would like to avoid. Thank you for reading. PS: if you happened to have ready equations, don't tease me, post'em.