GPS Caching

Accurate GPX data recording while in the woods requires the use of an active antenna. No GPS unit with an internal antenna will perform well under solid tree cover while riding.

GPS units are sold based on ease of use, so the manufacturers try to claim that their internal antennas are good enough, and while hikers move slowly enough for an internal antenna can get a good fix, mountainbike recordings require an active, external antenna to boost the signal strength enough to maintain a solid track. WAAS helps a lot but is still not good enough while biking in the woods. The manufacturers hide this data-quality fact so well that it is often challenging to find out whether a GPS unit even has an external antenna socket. The antenna manufacturers are often the best source for determining which GPS units have an external antenna socket.

For this reason, most of the MTB GPX data posted on the web is highly inaccurate, often up to 100' from the actual track. A sign that the GPX data is suspect is when the elevation data is jittery, caused by the position jumping around due to poor signal strength.

CascadeSingletrack GPX is recorded with a Garmin Colorado, which is a discontinued model, and so a cheap active antenna option.

Combined with an active antenna, most recordings are consistently accurate within 8', even in deep woods.

The Garmin units which support an external antenna use an MCX connector, so get an antenna with a short cable and a straight MCX connector.

For GPS units which do not have an external antenna socket, a repeater can be built, combining an active antenna with an output antenna, for the internal GPS antenna to pick up. There are some plans for these on the web, and one could be built using a flashlight housing. The active antenna has to be powered, and 3 AA or AAA batteries will work. The output antenna is wire cut to a specific length.

The Garmin GPSMAP is the best current-year model with an external antenna socket, and has been around for years so is a proven performer. GPSMap 60 60C 60CS 76 76C 76CS all have external sockets.