  The NewtonWigner basis of orthonormal localized states is generalized to
orthonormal and relativistic biorthonormal bases on an arbitrary hyperplane in
spacetime. This covariant formalism is applied to the measurement of photon
location using a hypothetical 3D array with pixels throughout space turned on
at a fixed time and a timelike 2D photon counting array detector with good time
resolution. A moving observer will see these detector arrays as rotated in
spacetime but the spacelike and timelike experiments remain distinct.
