A method of generating a topographical map of a region of a body of a subject for the manufacture of a body fitting article to be fitted to the region of the body, the method comprising the steps of: urging a contact probe, incorporating a first part of a 3D position sensing system, towards the outer surface of the body such that the contact probe is touching the outer surface of the body or separated from the outer surface of the body only by a barrier layer which is flattened against the outer surface of the body by the probe; and drawing the contact probe over the region of the body where the body fitting article is to be located such that the contact probe moves relative to a second part of the 3D position sensing system associated with a fixed reference fixture thereby to generate 3D positional data of the surface of the region of the body where the body fitting article is to be fitted and to generate a topographical map of the region; wherein, the method further comprises the steps of: using the reference fixture to locate a datum feature on the body that is spaced apart from the region of the body where the body fitting article is to be located; and using the probe to generate 3D positional data which is used to determine the 3D position of the located datum feature on the body by touching the probe onto a pre-determined datum location on the reference fixture of known relative position to the located datum feature on the body and capturing the 3D positional data generated at that datum location; and wherein the body fitting article is a helmet and the region of the body is the head of the subject and wherein the reference fixture is configured to stabilise and immobilise the subject's head and to locate the eyes of the subject, the datum feature being an eye socket of the subject. urging a contact probe, incorporating a first part of a 3D position sensing system, towards the outer surface of the body such that the contact probe is touching the outer surface of the body or separated from the outer surface of the body only by a barrier layer which is flattened against the outer surface of the body by the probe; and drawing the contact probe over the region of the body where the body fitting article is to be located such that the contact probe moves relative to a second part of the 3D position sensing system associated with a fixed reference fixture thereby to generate 3D positional data of the surface of the region of the body where the body fitting article is to be fitted and to generate a topographical map of the region; wherein, the method further comprises the steps of: using the reference fixture to locate a datum feature on the body that is spaced apart from the region of the body where the body fitting article is to be located; and using the probe to generate 3D positional data which is used to determine the 3D position of the located datum feature on the body by touching the probe onto a pre-determined datum location on the reference fixture of known relative position to the located datum feature on the body and capturing the 3D positional data generated at that datum location; and wherein the body fitting article is a helmet and the region of the body is the head of the subject and wherein the reference fixture is configured to stabilise and immobilise the subject's head and to locate the eyes of the subject, the datum feature being an eye socket of the subject. using the reference fixture to locate a datum feature on the body that is spaced apart from the region of the body where the body fitting article is to be located; and using the probe to generate 3D positional data which is used to determine the 3D position of the located datum feature on the body by touching the probe onto a pre-determined datum location on the reference fixture of known relative position to the located datum feature on the body and capturing the 3D positional data generated at that datum location; and wherein the body fitting article is a helmet and the region of the body is the head of the subject and wherein the reference fixture is configured to stabilise and immobilise the subject's head and to locate the eyes of the subject, the datum feature being an eye socket of the subject.