I am currently in the process of designing a spatial survey to assess the abundance/density of woody debris across an ecosystem with multiple defined habitats (i.e. I am interested in not only the abundance across the entire system, but also any differences across habitat type). I have no prior data or similar studies to perform a power analysis to help determine how many sites I will need to address my questions, but I do have presence-absence data of woody debris within my study area. Is there a way to use this data to inform my design? I am likely going to be developing a small pilot study to collect enough data to run a power analysis, does presence-absence data help in any way?