Ultra-high tech mapping the PCT: introducing the Long Distance Geo Logger

Well below our community’s radar, a team of volunteers have been working to build a custom GPS, and the software to power it, in order to make a highly accurate map of the Pacific Crest Trail. Here’s a glimpse into what they’ve been working on for the past year and a half. The team, made up of retired technology professionals, has built these custom Geo Loggers as a gift to the trail. The data is being fed into the Halfmile Project and the maps at pctmap.net.


Here’s the 12 gram circuit board. It logs raw GPS information that is post-processed for 10X accuracy improvements. The design is optimized for long running times.

The first GPS unit has hit the trail and a few more will be finished soon. They use expensive, highly accurate GPS chips, special antennae, and they are controlled by an iPhone. Prototypes were carried on the trail last summer.

The main half of the "Long Distance Geo Logger" with batteries, and the PCB.  The blue case was  designed and printed by Chris Dominik, a member of the high school robotics team. I painted a  solution of a especial epoxy on the outside to make it water tight.  Hot glue was used to seal the antenna connection at the bottom. I was unable to get the proper o-rings, so we made a gasket (not shown) that fits between the two halves.

Seen in its blue 3D printed case, the Long Distance Geo Logger will run for about five days on a set of batteries. The case was designed and printed by Chris Dominik, a member of Dal Brandon’s high school robotics team. The unit is watertight.

The goal for version 1.0 of the Long Distance Geo Logger is to generate a track and waypoint set for the Pacific Crest Trail at sub-meter accuracy and to know the degree of confidence behind each point. The trail has never been mapped with this level of accuracy.

Here, we are flashing the Geo logger with the program that we have been working on for the last six weeks.  Turns out that we produced well over 20,000 lines of code that reside in the Logger and the iPhone.

A huge part of the project is writing the code that runs the unit and post-processes the data. Here, David Lippke and Dal Brandon are flashing the Geo logger with the final program that they worked on over the last six weeks. More than 20,000 lines of code reside in the Logger and the iPhone.

This is top of the antenna mount. The orange "pipe" was 3D printed.  It connects the antenna to the adjustable angle clamp.  We actually printed two sides, but the side that goes into the pipe proved to be too fragile, and we had to resort to a heavier pipe clamp.

An external antenna is an essential part of a highly accurate GPS.  The orange “pipe” was 3D printed to support the antenna. They actually printed another piece, but it proved to be too fragile, and they had to resort to a heavier pipe clamp.

This is the entire antenna assembly... The loop at the bottom is to keep the assembly from twisting  in a pack.  The Geo Logger is connected at the end of the wire and carried in a pack.  Sorry, but I forgot to get a picture of the Geo Logger in its final configuration, connected to the antenna.

Here is the entire antenna assembly. The loop at the bottom is to keep the external antenna from twisting in a backpack. The wire at the bottom connects to the blue GPS unit.

The eponymous Halfmile, Lon Cooper, is carrying the first unit on his thru-hike this summer. The creator of the Halfmile App, David Lippke aka “White Jeep”, is the workhorse behind the code and design. David is the expert at converting GPS trail data into actual maps. Dal Brandon is the primary person designing and building the physical device. He also wrote a large portion of the code. Jeff Hayward provided critical design input at every stage of the project and also worked on coding and testing of the unit, especially regarding battery issues. Jeff also is the guru behind the theoretical aspects of GPS signals and differential post-correction. Rick Watson also worked on code and circuits. Their wives, significant others and friends deserve recognition for supporting this hugely time consuming and expensive passion.

Halfmile, using his iPhone to control the Long Distance Geo Tracker.  The Geo tracker is in the lower black side pocket of his pack.  You can see coiled coax right above it.

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.

Halfmile and Debbie, leaving the Junction at Highway 18 at Big Bear for the next leg of their hike. Notice that the GPS Antenna is almost perfectly level (a requirement for high accuracy).

Halfmile and Debbie, hiking north near Big Bear, California, carrying the new unit a few days ago. Notice that the GPS antenna is almost perfectly level (a requirement for high accuracy).

We’re looking forward to seeing the results at summer’s end. It’s possible that this technology will be made available for mapping other trails in the future, but at this time, the focus is on the Pacific Crest Trail.

Screen caps for the iPhone application that runs the logger.

Screen shots for the custom iPhone application that controls and monitors the logger.

The Long Distance Geo Logger is just a piece of the Halfmile Project. We’ll be sharing more views into this project, and other remarkable PCT volunteer projects, in the future. It’s this type of passion that makes the Pacific Crest Trail experience what it is.

Check out some of the Halfmile Project’s great work:

Author: Jack "Found" Haskel

As the Trail Information Manager, Jack works to connect people to the PCT. He's involved with a wide variety of projects that help the trail, the trail's users and the community that surrounds the experience. He has thru-hiked (Pacific Crest Trail in 2006; Colorado Trail in 2008; Continental Divide Trail in 2010) and is an obsessed weekend warrior.