How Accurate is Garmin MapSource?
About four months ago I bought a Garmin Legend Cx hand held GPS receiver and the Garmin Mapsource Canada Topo discs containing the topographical maps for all of Canada. I was surprised that most of the more popular trails in areas like Banff and Lake Louise appear on the topographical maps. For most of Kananaskis, which is where I prefer to hike, the trails are not included. Not a big deal because I did not expect that the maps would be included in the first place. As far as accuracy, mountain trails are not highways, depending on things like erosion, fallen trees, I would expect that the location of the trail would not be 100% accurate. Also, the sun, tree cover, cloud cover, and several other things interfere with the quality of the signal received by the GPS unit.
For this post I am only going to refer to hikes for which the quality of the satellite signal I was receiving was excellent.
Marsh Creek Trail near the Cave and Basin, which is a World Heritage site, should be a good example where one would expect a high degree of accuracy from Garmin.
The thin dotted line is the trail. It is tough to see in this post so I am sure you can imagine how hard it is to see on the 3x6 screen on the hand held. About 20 of the 140 recorded points are on the trail as reported by Garmin. The track is off the reported trail by up to 75 meters. Really not a big deal because the trail was easy to follow on the day I did the hike. Interestingly, the Bow River seems to have moved but then again, rivers do that.
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Another area, world-renowned Lake Louise. Saddleback Pass is a very popular trail. For this hike I would estimate the track was on the trail as reported by MapSource about 80% of the time. This short section was in a tree-covered area. The trail was very well defined, it is not like it was in a rock slide area and has changed over time. I had a very good signal and the trail is off at times about 100 meters.
A few weeks ago I did a short hike. I am going to call this one Victor's Hike in honour of our fearless guide. We basically hiked across Lake Louise to view the Victoria Glacier. Here is the topographical map I generated with MapSource.
I have been to Lake Louise numerous times. I strapped on my snowshoes on land, MapSource says I was about 100 meters from the shore on the lake. At waypoint #53 there was definitely water below my feet, more than enough to drown but Garmin puts me standing on the lake edge. From waypoint #53 to #54 and return I would estimate that I was much closer to the middle of the lake than shown on MapSource.
My conclusion at this point, my Garmin unit will likely help me figure out if I am on the right trail, it will certainly get me back to my car but if my Garmin unit shows you are anywhere near water, be alert because it is not accurate. Luckily, it is waterproof to a meter.