New Marathon training route

It says it is 15.5 miles, but I suspect it is actually further since I had to guess at the route through the woods--you cannot see the path on the map. I know from timing myself that my road pace is around 8 minutes per mile and while I spend more than 12 minutes in the first section of woods, the mapping gives me less than one mile: It is probably more like 1.5 miles. Similar analysis of the second wooded path indicates it is short by 1/4 to 1/3 mile. All these errors taken together probably push today's route to just shy of 17 miles. Maybe next time I will keep it all on the roads to make it easier to measure.