Not flying today, but I was looking at weather this morning at the airport. The visibility is reported as 3 miles mist, winds calm. But is that 3 miles horizontal or vertical? At 3 miles, you should be able to clearly see down the runway, but if it is vertical, then the actual horizontal range could be much less. Take off or not? I know from local observations and history that this is a common morning thing because the airport was built next to a swamp. It is not pervasive in the area and once at 100’, the visibility is greater than 10 miles with most stations near by reporting clear.