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Handheld or Wrist GPS Units for Hikers?
Professor Gérard Lachapelle
Canada Research Chair in Wireless Location
University of Calgary
A question facing GPS equipment buyers for hiking activities is which unit to select among the increasing large choice offered by suppliers. The equipment can be divided into two categories, namely hand held and wrist held. Hand-held units have batteries lasting 15 to 25 hours that can be changed in the field, a must-have feature for multi-day hikes. Screens and large memories allow one to upload and use maps in electronic format, an additional feature, although the use of a paper map to better navigate and identify topographic features is always preferable, especially for off trail hikers. I use Garmin units, the recent series of eTrex (10, 20 and 30) now being my favorites because of their combined use of GPS and GLONASS, the latter being the Russian equivalent of GPS. The eTrex 30 model also has the capability to record the heart rate wirelessly if the user has a monitor on the chest. GPS-GLONASS accuracy is not better than when using GPS alone under open sky (like on a ridge top) but can be in narrow valleys. An example of a well known trail falling in the latter category in the last 500 m to Ribbon Fall due to the high elevation of mountains each side of the trail. The situation gets worse when hiking all the way to Ribbon Lake. In these areas, GPS alone can give erroneous positions due to limited satellite availability. In very narrow canyons like King Creek in Kananaskis Country however, even a combined GPS-GLONASS unit will fail to provide continuous and accurate positions, as expected. Since all hand held units include integrated antennas, location of the unit on the hiker can make a difference. Good locations are a pocket on the upper part of the body or on the upper part of the hiking bag.
An interesting alternative to Garmin hand held units for the safety conscious hiker is the Delorme Earthmate PN-60W, which can be coupled with a Delorme inReach two-way message communication system as shown to the left. inReach uses the Iridium satellite communication system and is available worldwide. Short messages can be sent and received. A panic SOS button is available in case of emergency. In this case, the user’s location is related to the rescue service in the area. I have not used this system myself as I have a two-way voice satellite phone that uses Iridium as well. The latter is more flexible but it requires one to turn the unit on, wait for satellite availability (up to 10 minutes) and enter the full phone number, not an ideal situation in case of a heart attack, fall or mauling by an animal. A simple SOS button is an advantage in such a situation… at least to recover the hiker’s body. Both systems require subscription fees that are significant.
Wrist held GPS units are now available from various manufacturers. Due to their features, I use the Garmin 310XT and 910XT models, the latter being shown to the right. I use a heart rate monitor with them. Position and navigation performance are as good as those of the hand held units in most situations, despite compactness. The 910XT has a barometer which can be good to improve height gain accuracy but I have not seen significant differences with the 310XT model during the two months of testing since the availability of the 910XT. Batteries last up to 20 hours but are not interchangeable in the field but must be recharged with an external power supply. The small display would make map reading difficult, were map uploading be an option. Position coordinates can be displayed however making navigation with a paper map still possible. Each display can feature up to four different data windows (three shown in the picture of the 910XT). One can additionally sequence through different displays with a simple button. Hence the hiker can conveniently monitor distance travelled, height climbed, heart rate and calories burned, still while using hiking poles. This is truly impressive, informative and good to monitor wellness. I have been intrigued by the calorie count method, and have seen variations of 10 percent between successive hikes of Prairie Mountain at the same pace. Once the age, sex, weight and fitness level of the user are entered, the calorie count is based on heart rate increase. Consultation of books and colleagues in Kinesiology and Medecine on our campus made me realize the complexity of precise human body calorie expenditure. To make a long story short, a 10 percent day-to-day variation is normal due to nutrition, muscle tiredness, etc. This is still very good and it is fun to watch calorie spent, although it is much less than I had hoped for…hence the size of the after-hike ice cream is decreasing.
All Garmin units data can be downloaded and used by the Garmin Connect website or the Garmin BaseCamp software (Windows and Mac versions) to display and preserve the trajectories in gpx and other format files. The website preserves the position and heart rate data.
In summary, for the avid hiker, having both a hand held and wrist held unit is a good option. For day hikers in the mountains and walkers/joggers in the city or elsewhere, the wrist unit is the preferred choice.
The author has been involved with GPS signal processing development and research for 32 years and was part of the original group of engineers who started GPS research and applications in Calgary in 1980. He has no financial or other interest in Garmin, Delorme or GPS Central.
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