Why is the A.T. Guide final mileage different than ATC’s final mileage?

Each year we gather reroute information all during the year and then wait for the ATC to release their final mileage to compare and make any last minute adjustments. This final piece of information comes in at Thanksgiving each year. This is why, while our updates are finished by October, the A.T. Guide historically doesn’t ship until mid-January. In 2021 supply chains and print lead times became slower than ever and we had to make the decision to go to print much earlier in order to avoid extraordinarily late shipping dates. This means we have to make our calculations before ATC releases their “official” mileage. In many ways this makes us work harder to make sure everything is correct. We still get the official number from ATC around Thanksgiving but we have to wait for actual data in January. Anything we may have missed we post in the PDF and on our online updates page. A pleasant side effect of this process is the PDF is immediately available for download in November and the A.T. Guide books arrive in time for Christmas shipping deadlines. Rest assured, anything we might miss as a result of our new process is small and confined to local areas on the trail.

2023 Difference Explained

1. The bulk of the difference between our mileage and The ATC official mileage is in NY. We were aware of, and make specific mention the Palisades Parkway detour. ATC actually put +3.0 mile number to it.
2. We included the Forth Mountain Relocation.
3. We included the remeasures for Mass & Connecticut. There were a few places where we had to guess how ATC might round up or down to the next tenth of a mile because it was right on the edge.