Based on your first sentence, what you are trying to convey is a condition of data collection. There are several ways to do this: some examples are below, think about which one is most consistent with what you are trying to say:
(1) These data were recorded with a distance of 500 meters between every two observation points.
(2) Each of the observation point was approximately 500 meters from any other point.
(3) The conditions for observation included a distance of 500 meters between each point, _______*state any other conditions in this same sentence in a list*
The main idea is that if you want to describe a condition without using the phrase "under the condition that" you can either just state the condition (like in 1 and 2) or make a list of conditions. There are other options as well- these are just examples.