The Flora of the PCT: Accuracy of Reported Trail Mileages

Mileages and elevation gains are always a bit problematic for trails, and shouldn't be taken as being accurate to the last decimal point. For the PCT, in particular, the trail is always changing. The trail shown on the USGS Topo maps is quite commonly different from the trail shown in the Pacific Crest Trail book by Schaffer et al. In general, the actual trail is usually exactly that shown in the Schaffer book, since the Topo maps are much older. However, segments change yearly, and we know of several segments in southern California that now differ from the version in the 1995 edition of the Schaffer book.

Even if one has the same version of the trail, the reported mileage is hard to determine accurately. Some of the problems are:

Hence a given mileage on any trail is probably never more accurate than 5 to 10%.

Examples: if a trail segment is 1.0 mile, that is probably accurate to 0.1 mile. But if a trail segment is 10.0 miles, that is probably accurate to only 1.0 mile. The error remains at about 10% as one adds together segments. Hence "Mile 100.0" on the PCT measured from Mexico, is probably only accurate to 5 or 10 miles.

Because it is fun to know how far a given segment is from Mexico, we have given the mileage from Mexico for each segment. We've arrived at that number by using the segment lengths we've adopted for each section, and then rounding the number appropriately.

Thus segment A1 covers miles 0.0 to 2.3 from Mexico, which is probably accurate to 0.1 mile. But even if a segment at mile 100 is said to cover mile 99 to 102, with no tenths of a mile quoted, the accuracy is much higher than one mile, and that segment might actually cover mile 97 to 100.

The mileages we quote from Topo! are those derived either from our own GPS track of a segment, or using Half Mile's GPS track. We also quote the mileage from the PCT Data Book from the PCT Association if it is different from the Topo! estimate. We use our best estimate, along with some rounding, to determine the mileages we give for each segment. In general, we err on quoting a larger distance, since hikers are never unhappy if a trail turns out to be slightly shorter than advertised, but are often very unhappy if the trail turns out to be a mile or more longer than advertised.


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Copyright © 2014 by Tom Chester, RT Hawke, and Shaun Hawke.
Permission is freely granted to reproduce any or all of this page as long as credit is given to us at this source:
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Comments and feedback: Tom Chester
Updated 4 December 2014.