A procedure for determining the available accuracy of satellite image-based positioning is proposed. The procedure is intended to evaluate the accuracy-related performance of Earth observation system. The procedure allows us to determine errors in positioning based on satellite Images without any reference points. Effects of the following errors in measurement of exterior orientation items are considered: 1) errors in the measurement or prediction of the spacecraft COG position, 2) spacecraft design errors, 3) errors in the measurement of spacecraft orientation angles. The following types of errors are analysed: 1) errors in the determination of object geographical coordinates (in angular measure), 2) errors in the determination of object coordinates along tangent and binormal to orbit (in linear measure). As an example of applying the procedure, results of analysing the dependence of limiting aggregate errors in positioning on the following design parameters of Sich 2 space system are presented: 1) orbital height, 2) nominal orientation of optical axes of the optoelectronic system, 3) object positions in satellite image.