Not an exact science
Sometimes bees go in somewhere and walk to the hive. This was the case with this hive. They walked into a hole on the side of the house. I used my thermal scanner and thought I had found them. The condo’s carpenter removed some of the siding and trim. We couldn’t find them. So my wife tried the porch roof and there they were! We had the carpenter cut a hole and we removed the hive and bees. Knowing exactly where they are is not an exact science. We use what tools we have and the knowledge we have gathered over the years.