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April 24, 2010
I am often asked this question. Prime considerations include cost, power autonomy, weight, functions and robustness. Cost ranges from approximately $100 to $600. Important specifications include the use of a high sensitivity GPS chip inside the device. Most if not all handheld devices now have this feature. Such a chip allows signals to be acquired and tracked under non line-of-sight (to the satellites) conditions, such as under the forestry canopy, which is highly preferable for hikers. It also provides flexibility as to where the device can be stored, such as in a pocket and inside a backpack. If one stores the unit in a backpack, it should be in the upper compartment to minimize signal attenuation thereby improving accuracy and saving battery power.
I will use the Garmin series (http://www.garmin.com/garmin/c.....nthetrail/) as examples below (No I do not have a financial interest in this company).
Weight is not an issue as the range is typically between 150 and 200 grams. Specified power autonomy is typically between 10 and 25 hours using two AA batteries under ideal conditions, which means line-of-sight. Unless the unit is placed on the head (quote uncomfortable…), the signals are not line-of-sight and the above autonomy will be somewhat lower. Likewise, low temperatures will decrease power autonomy.
Functions are great but require patience and training to learn and remember (As my wife tells me when I look enviously at new cameras, don’t get the advanced model, you are not patient enough for it…). The lower end models can usually only provide positions and waypoints (e.g Garmin e-Trex H with a plastic housing). Having a track function allows one to continuously track one’s trajectory and display it later on the computer. This is nice to keep track of one’s hikes, prove to others where you have been… and boast to your friends how good you are. A prime example of such a mid-range device is the e-Trex Vista HCx that has a good colour screen, a robust metal housing and a specified battery life of 25 hours. These mid-range units currently cost $250-$300. Reliability is usually excellent and there are plenty of functions to play with. Then come the high end units with touch screen, cameras, etc. A prime example is the Garmin Oregon series. Nice and easy to use, $500+. Is there a difference in accuracy between units: Not at the level of a few metres, as required for hiking. What affects the accuracy for hiking is the presence of signal obstructions, such as mountains… Using GPS at the base of a vertical rock wall will result in poor accuracy due to the poor geometry of the signals coming from the satellites which, by the way, are all over the sky. On a ridge, where open sky prevails, an accuracy of 1-2 m is no longer unusual.
One should learn to use all functions by READING the manual and practicing in the neighbourhood before venturing in the backcountry (Reading such a device while walking on a rocky steep trail is not a good idea as I learned myself coming down Fairview Mtn last Spring…). This includes setting the various functions needed for one’s use. GPS should be turned on. WAAS if available should be turned on as it improves accuracy by allowing measurements on additional satellites that are in geostationary orbits. The right reference system (datum) should be used. For the Canadian Rockies, users of Gem Trek maps should use WGS84 (which is the same as NAD83 at the accuracy level needed by hikers). Some NTS (National Topographic Series) maps are still in the NAD27 reference system and the necessary change should be made in the device settings in this case. Then learn how to create waypoint, tracks, etc. What about an electronic map for the device and the computer at home? I suggest that one buys them from the GPS device provider. The Garmin one (purchased separately) for example comes in one file; the latest version (4) can be displayed in 3D on the computer. NTS maps can be downloaded freely from the NRCan website. These are generally of high quality but precisely because of this attribute, they are not stitchable in one piece due to map projection constraints and convergence of meridians.
Software is needed to download the tracks from the device to a laptop and display them on maps. The Garmin software (BaseCamp comes in a PC and Macintosh version and can be downloaded free of charge). The software is capable of showing the tracks on Google Earth (Software for the latter can be downloaded freely from the Internet). Tracks saved as .gpx can be transferred to other GPS devices and computers.
The do’s and dont’s: If one walks off trail where the device is used for serious location and navigation, bring spare batteries. Use the track function to retrace the path in case of problems. Mark waypoints at critical locations for retracement in case of problems with the track function. In forested areas and ridge walks when a storm or heavy fogs can come in quickly, a device failure could become a critical issue. Always bring a paper map and a traditional compass and know how to use these for orienteering.
What about if an accuracy better than a few metres, say a few centimetres is needed, as the Canadian Olympic Ski Team have been using for their training since 2007? As with any technology, complexity increases rapidly with performance gain. Leave this one to GPS engineers.
Enjoy GPS on the trail!
April 14, 2010
Some other observations:
1) The high sensitivity is essential. My Vista Cx (predecessor to the high sensitivity HCx) is virtually useless as described here http://drandkc.blogspot.com/20.....sucks.html
2) Mac users need to keep expectations low. Connectivity with either Magellan or Garmin units is marginal. Pre-planning routes using Garmin's maps is only possible if you can run a PC emulator first because the Garmin's proprietary maps are not Mac compatable. I solved this buy buying the maps on a micro-SD card that is installed in the Cx, but therefore have limited trip pre-planning capability. The Calgary Trail Mapping Project is a notable case of a lot of potentially useful tracks that cannot be used by Mac users without intervention from the CTMP people.
3) Speaking of pre-planning, without much skill, it's pretty easy to set waypoints in Google Earth, export them as .KML files, convert them to .GPX files, and upload them to the Vista.
4) Also as described in the above post, they couldn't have made the user interface any more counter intuative if they had tried on the Vista. These things are not for the "VCR still flashing 12:00" crowd.
5) I still have great difficulty equating the UTM coordinates with the GemTrek maps even though the GPS's settings are correct.
6) Past experience: just when you need it most, you will lose the signal. People who rely on their GPS 100% wil be in trouble. So always bring a map and compass and know how to triangulate an approximate position by siteing a bearing to a known landmark. And because batteries run out, don't assume the map in the GPS will always be available even if the GPS has no signal.
December 8, 2008
I have had a Garmin GPSMAP 60cx since they first came out and get a good signal most of the time. I find though that the number of satellites visible is the most significant factor in getting a good tracklog and accurate waypoints. Even in open country satellite coverage varies considerably over the course of a day. I chose the 60cx rather than the 60csx (with altimiter and digital compass) because of the better battery life.
We work exclusively on Macs and use MacGPS Pro sofware, http://www.macgpspro.com/. None of the map sets are up-to-date for our area of the Rockies.
April 15, 2010
I have been using the Ibycus mapset for a few months now, and have been very happy. It's seamless, works great, and fairly detailed. Oh, and free. I'd never recommend buying maps from garmin.
What's amazing to me is to think back to when I was a kid and in scouts. On camping/hinking trips we used a magnetic compass and paper maps to navigate!!! Times sure have changed. And of course it's important (although most people to my knowledge don't do this) to know how to navigate without a GPS. They can lose battery power, get lost, break, and all manner of things to cause them to stop working. Great to have, of course, when they are working, but good to know how to manage without as well!
January 13, 2014
I have had a Garmin Dakota 10 for the last 3 or 4 years. Had a Garmin Etrex Legend for many years till it decided to pack it in. I don't use or rely on GPS as others do. Mainly it gets used for distance and elevation readings. I do use it to input in my favorite trails or the trail I happen to be on for the day. The track back feature is nice, especially in a blizzard or thick brush. Used it in all kinds of weather conditions and there was only one occasion where I didn't have a clear signal. Otherwise, in the valleys, in the forests, to the summit of a mountain, it has performed well. I haven't used the mapping software as I am more of a map and compass and remembering landmarks individual. For what I use it for, it works well.
I am using Gpsmap 64s since last year and it works like a charm, no issues found so far.
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