At measurement of co-ordinates of objects in radar-tracking, optic-locational and so forth systems traditionally it is considered that the best measuring instrument of co-ordinates and on simplicity of hardware realization, and on accuracy of measurement of co-ordinates is measurement by criterion of the maximum credibility. It is show that the split-hair accuracy of measurement of co-ordinates such measuring instrument corresponds to only not deformed forms of signals. The top estimation mean-square measurement errors by criterion of its minimum for the typical form and typical distortions of the form of signals of type “smaza” images is received.