  The ambiguity function of a spatial signal in the "signal spatial frequency
displacement vs antenna linear displacement" coordinates is considered in this
paper; in case of a monochromatic signal with known carrier frequency, spatial
signal vector angular displacement is considered as the second coordinate. The
analysis is made taking into account an external (reradiated or thermal)
background which contributes considerable peculiarities in the properties of
the spatial ambiguity function. Accuracy of measuring the signal linear or
angular displacement and resolution are determined. Examples for the Fresnel
and Fraunhofer zones are given.
