a component configured to obtain captured image data representing an image captured by an imaging device associated with the portable apparatus;
a component configured to obtain mesh data representing a 3-dimensional textured mesh of at least part of the environment;
a component configured to process the mesh data to generate a plurality of synthetic images, each said synthetic image being associated with a pose within the environment and being a simulation of an image that would be captured by the imaging device from that associated pose;
a component configured to analyse the plurality of synthetic images to find a said synthetic image similar to the captured image data, and
a component configured to provide an indicatidn'of a pose' of the portable apparatus within the environment based on the associated pose of the similar synthetic image.
13. A device according to claim 12, wherein a lens of the imaging device comprises a wide angle lens.
14. A vehicle including a device according to claim 12 or 13.
15. A computer readable medium storing a computer program to operate a method according to any of claims 1 to 11.