With the warming of the climate and the resumption of the Northern Sea Route, studies of the dynamics of the northern deltas, that close the exit to the ocean, have intensified. The best way to detect changes is to compare images, obtained at the end of the last century from the Landsat/ETM satellite (resolution R = 30 m) and modern Sentinel-2/MSI images (R = 10 m). To identify the effect of differences in the resolution of the compared images on the accuracy of determining changes in the coastline, a graphical simulation of reproducing changes (areas of coastal erosion or sediment accumulation) at the pixel level was performed. Reproduction of changes had been simulated for coastlines, that coincide in the direction of the pixel grid lines and deviate from them at angles of 15°, 30°, 45°, when the coastline is shifted from 10 to 40 m. It has been revealed that it is possible to determine the displacement of the coastline starting from the value of 20 m from multitemporal images with a resolution of 30 and 10 m. For coastlines directed along the pixel grid lines, it is possible to downplay (or exaggerate) the washout (or accumulation) band by 1/2 RL + 1/2 LS = 20 m. Coastlines that are tilted to the pixel grid may show false changes, especially if the shoreline position is unchanged or the offset is small (10 m). The kind of the distortion strongly depends on the position of the real coastline within the large Landsat pixels. The greatest distortions are characteristic of coastlines that occupy a peripheral position in the cells of the pixel grid. The simulation results should be used when preparing palettes to determine changes from combined multi-temporal images.