1. A method for estimating a pose of a camera relative to a surface upon which a 3D object rests such that a volume can be estimated for that object in an image captured by that camera, the method comprising: determining a matrix K from parameters intrinsic to a camera used to capture at least one image of an object for volume estimation purposes; determining a camera translation vector T=[t X t Y t Z ] relative to a set of real-world reference coordinates in (X,Y,Z); determining a camera rotation matrix R from camera angles (φ,θ,ω) relative to the X, Y and Z axis, respectively, of said real-world reference coordinates, wherein said camera translation and said camera rotation are determined from depth values associated with pixels of a surface of said object, said depth values being measured by a depth sensor of said camera; and estimating a distance Z c of said camera, comprising: Z c ⁡ [ i j 1 ] = KR ⁡ [ X Y Z ] + KT T wherein K comprises: K = [ f 1 α ⁢ ⁢ f 1 c 1 0 f 2 c 2 0 0 1 ] , where f 1 and f 2 are focal lengths of a lens of said camera in each of two directions, α is a non-zero skew of a sensor of said camera, and c 1 and c 2 are center positions of said camera in pixels, and; wherein R comprises: R = [ 1 0 0 0 cos ⁢ ⁢ φ - sin ⁢ ⁢ φ 0 sin ⁢ ⁢ φ cos ⁢ ⁢ φ ] ⁡ [ cos ⁢ ⁢ θ 0 - sin ⁢ ⁢ θ 0 1 0 sin ⁢ ⁢ θ 0 cos ⁢ ⁢ θ ] ⁡ [ cos ⁢ ⁢ ω - sin ⁢ ⁢ ω 0 sin ⁢ ⁢ ω cos ⁢ ⁢ ω 0 0 0 1 ] .