Easy, 2,650 Miles, right? Well… not quite.
The question of the PCT’s length comes up often, with guidebooks, phone apps, and other sources across the internet offering varying figures. In recent years, PCTA has come a long way in better tracking and calculating distance. While we regularly reference the rounded figure of 2,650 miles as shorthand for the trail’s length, our current best estimate places it at approximately 2655.8 miles. It’s complicated because the length actually varies year by year, and homing in on highly accurate mileage for a trail that spans thousands of miles can pose significant challenges. We know that trail mileage matters a lot to PCT trail users. Read on to discover some of the complexities involved in determining the true length of the PCT.
Northern Terminus, Photo by: Ryan Weidert
It Moves!
Sometimes, the trail gains a mile or two, or sometimes, the trail shaves off miles (you’re welcome thru-hikers!) You might be thinking… how does this happen, isn’t the trail already on the ground? While true, PCTA, alongside managing agencies and dedicated trail crews, continually refines and optimizes the trail’s route. These efforts range from minor adjustments to larger-scale relocation projects aimed at enhancing the overall trail experience. For instance, routine maintenance often involves realigning sections of the trail to improve sustainability, such as adding switchbacks or adjusting trail tread within the existing corridor. These alterations might end up making the trail a bit longer or shorter, typically on the order of hundreds of feet. Pretty small potatoes when looking at a trail that crosses thousands of miles. Other times, the PCT undergoes bigger relocation projects based on a process called Optimal Location Reviews (OLR). These relocations can be significant and can take years to complete. These projects aim to relocate the PCT to a location better suited to providing a natural setting, scenic beauty, and safe public access, among other things. As a result of these projects, the trail’s length may fluctuate by several miles. But they also end up making the trail safer and more enjoyable for all.
The Sierra Buttes Relocation – Old decommissioned PCT shown in dashed black line, current PCT in maroon.
What’s so hard about miles?
Calculating distance across such a large geographic extent is challenging. Even minor inaccuracies that are repeated hundreds of thousands of times compound errors, resulting in significant discrepancies in overall mileage. For example, if each point in our PCT dataset were off by 1ft, the margin of error would be over 200 miles. Additionally, the translation from a three-dimensional Earth to a two-dimensional map necessitates “projecting” data in GIS (Graphical Informational System) software, which can introduce different types of accuracy loss. However, advancements in technology offer us promising avenues for improvement, such as using LiDAR (laser scans of the earth) to more precisely capture and map changes to the trail.
A little bit about the data
PCTA’s current iteration of PCT mapping data is built upon data that was donated to the organization from the Halfmile Project. You may have heard of Halfmile, he and his team are kind of a big deal. The resulting data from this project’s multi-year effort was the best, most accurate data for the PCT of its time. Volunteers in the project mapped thousands of miles of trail with survey-grade custom and commercial GPS units and spent tremendous amounts of time analyzing, processing, and curating the results.
Halfmile, using his iPhone to control the Long Distance Geo Logger. The blue GPS unit is in the lower black side pocket of his pack. You can see coiled cable right above it.
Building on this legacy, PCTA now builds upon that same highly accurate data from Halfmile, revised to account for re-routes and trail reconstruction that have happened since PCTA assumed control of the data. We maintain our PCT Centerline (the line data for the trail’s location) and Mile Markers (points every tenth or half mile), with new versions released on an annual basis, usually in January. The data is displayed on our Interactive Map and made available on our PCT Data webpage, freely available for download in a variety of formats. By fostering an environment of transparency and accessibility, we empower trail users, app developers, and agency partners alike to utilize this standardized dataset, facilitating seamless communication and navigation along the trail.
Graceland takes an emotional moment at the Northern Terminus after an adventure of a lifetime. Photo by: James Townsend
Conclusions
As we continue to monitor changes, refine our modeling of the PCT, and offer it to users in new ways, we realize that our data remains imperfect. Digitally representing the complexities of the natural world always is. Despite this, the Association’s renewed prioritization of data management, built upon the invaluable foundation set by the Halfmile project, marks significant progress in this work. We recognize that our path toward data accuracy is ongoing and that we’re by no means at the finish line (approx. 2,655.8 😊), but we’re always improving, collaborating, and working to celebrate the intricacies of the PCT in this unique aspect of our work.
For any questions or comments, please contact me at [email protected]