Adams Canyon


E-Mail Jeff

View Looking back down the canyon from the waterfall

This is a short hike I did after work to a waterfall in a canyon that often causes me GPS reception problems due to the terrain, and tree cover. On this trip I carried a Sportrak, and an eTrex, with both receivers carried in my hands for about half of the journey, and on the top of my camelbak straps for part of the trip with the etrex horizontal on top of my shoulder, the Sportrak vertical with the antenna above the level of my shoulder.

Thrown off position in middle of track, the Sportrak lost reception for a bit here, however the track is shown as unbroken.

Ricochet rabbit effect near Waterfall

As you can see, the Sportrak experienced some reception problems in this canyon, as is normal for every receiver I've ever tried. While the unit indicated loss of reception on occasion, the tracklog doesn't show any gaps. It does appear to have suffered from multipath interference problems in a couple of areas with the area at eastern end of the hike exhibiting what I often refer to as ricochet rabbit syndrome. It also appears that the up and down legs of the hike show slightly less positional consistency than that shown on the eTrex track, which you'll see if you download the maps overlaid on the TOPO. On this particular hike the the up and back tracks match up fairly well, but so far I've found the Sportrak to be less consistent in this area than the eTrex. Surprising given the accuracy I've been getting when logging a fixed position.

Here is the area midway through the track where the Legend lost reception

The east end of the Hike near the waterfall, where the Sportrak was doing the Ricochet rabbit, the Legend simply stopped logging.

The Legend lost reception in a couple of areas on this hike, as shown by the gaps in the track. In one area you can see the obviously misplaced trackpoint, while on the eastern end of the hike near the waterfall reception was lost completely as evidenced by the gaps in the track. On this trip the Legend seems to be slightly more consistent in recording the up and back legs than the Sportrak was, quite possibly a result of more trackpoints being recorded.

As you can see, both receivers struggled somewhat on this hike, but they both did a reasonable job of recording my journey in some pretty tough conditions for a GPSR. The eTrex in the auto normal mode recorded 349 trackpoints where the Sportrak in it's most detailed setting recorded 221. The distance of the Legend tracklog is 3.4 miles where the Sportrak logged 3.8, the difference most likely being a result of the area where the Legend lost reception, making it read short while the Sportrak took a little side journey making it read a bit high.

As for which receiver did the better job, it's a tough call. The tracklogs both do a reasonable job of recording my journey. Both receivers had some reception problems as a result of both tree cover in areas, coupled with terrain blocking much of the sky and making conditions ripe for multipath reception problems. Watching the satellite status page, the sportrak often appeared to be getting better reception, but while watching the compass and map pages, the eTrex appeared to be updating quicker and more accurately, making it hard to determine which one actually was getting the better reception. In the end, even in this somewhat tough to navigate via GPS area, I wouldn't have any trouble finding myself around with either receiver.

For the actual tracklog data:

Adams canyon Tracklogs Legend/Sportrak

Here you can view the two complete tracks overlaid on a TOPO map:

Sportrak Track   174 KB

Legend Track    174 KB