Suppose that we do not have any way to measure distance, but do have clocks. There are N observers, who can all see the distant events, say spaceships taking off and landing on far away planets. The question is: assuming the speed of light is constant, can we deduce the distance to the events and other observers based on differing delays? What is the minimum number of observers/observations required? I know this is a general question, but I would be interested in a general solution, and any necessary preconditions.