Assessment of spatial resolution and linear resolution on the ground is an important task of quality control of the target equipment of space complexes of remote sensing of the Earth. A generally accepted, direct way to evaluate linear resolution on the ground is to visually decipher images of test-objects that represent special dashed worlds.
The purpose of this article is to develop a method for evaluating the probability of decryption of a standard three-spanned test-object with a spatial stroke frequency equal to the Nyquist frequency according to existing decryption criteria. Based on the formulations of the criterion for visual decoding of aerospace survey materials, expressions are derived that are suitable for calculating the probability of decoding a three-spanned test-object with a spatial frequency corresponding to the Nyquist frequency. The article substantiates the possibility of using the obtained expressions for a priori and a posteriori evaluation of the quality of observation materials. The efficiency of the method was evaluated by mathematical modeling using "hard" and "soft" criteria for image decryption. The "soft" decoding criterion allows for the possibility of "jumpers" between neighboring test-object strokes in the image. From the simulation results, it follows that to achieve the same probability of decryption by the "hard" criterion, the signal-to-noise ratio must be approximately 1.3...1.4 dB (25...27%) higher than when evaluating the probability by the "soft" decryption criterion. The method considered in the article is suitable both for a priori evaluation of the expected quality of digital optical-electronics systems, and for their a posteriori evaluation in the absence of bar codes on images. Enough information about the noise level, the level of the useful signal, and the decryption criteria used. If there is an appropriate software and methodological support for the assessment, it does not require the involvement of a group of qualified experts, just one trained operator.