We discussed a lot of factors that affect what image analysts call resolution, but in the end, the consideration of what is useful resolution is fairly simple. We just need to ask ourselves the question:

When looking at the image at the pixel level, can I reliably identify the links connecting objects or the gaps separating them?

If we can answer that question in the positive then we can say that we have enough resolution in the image. If not, then considering the factors above should help in formulating a strategy to try and improve the resolution of our images. Of course, in the end, some compromises will most likely be required, but we should then be in a better position to judge the limitations of the analysis capabilities.