Note to all you mile-conscious Appalachian Trail thru-hikers: Your trail data book is out-of-date. Latest measurements show the foot path is now 2,180 miles on the dot, up nearly 2 miles from 2009's length.

Each year the Appalachian Trail Conservancy reassesses the length of the Appalachian National Scenic Trail via information provided by volunteers who always seem to be at work improving the trail. And according to that data, which was pulled together by Daniel D. Chazin, of Teaneck, New Jersey (a volunteer who has been doing this re-calculation since 1983), relocating parts of the trail and remeasuring other sections this past year have added 1.9 miles to the length of the AT.

This year, increases were reported for Massachusetts–Connecticut (0.2 mile), New York–New Jersey (0.9 mile), central Virginia (0.1 mile), and Tennessee–North Carolina (0.9 mile), while the southwest Virginia mileage was reduced by 0.1 mile, according to the trail conservancy, which reflects those changes in its 2011 data book.

“The Appalachian Trail Conservancy’s 2011 Data Book is an essential planning resource for any Appalachian Trail hiker; whether they are out for a day hike or hiking the entire length from Maine to Georgia,” says Brian B. King, the conservancy's publisher.

Each year, the $6.95 Appalachian Trail Data Book is a top-selling official guide to the longest continuously marked footpath in the world—it condenses into 96 pages the high points of the series of guidebooks and maps. Information is presented at a glance in the same geographic units as the guides, with elevations for major points. Shelters, campsites, water sources, road crossings, supply sources, off-trail lodging, eateries, and post offices are all easy to identify in the Data Book.

For more information about the 33rd edition of the Appalachian Trail Data Book or to purchase a copy, please visit www.atctrailstore.org or call 888-287-8673.