*** GPS Cold Weather Operation *** Message : #23136991 From: A P R Cooper Address : aprc@pcmail.nerc-bas.ac.uk Length : 448 words Subject : Re: Handheld GPS in cold weather Posted: Thu, 9 Mar 1995 11:34:41 Org. : British Antarctic Survey In article <3jlmj5$9q1@news.bu.edu> mhuang@buast7.bu.edu (maohai huang) writes: >From: mhuang@buast7.bu.edu (maohai huang) >Subject: Re: Handheld GPS in cold weather >Date: 9 Mar 1995 01:45:09 GMT >Markus Bjorksten (mfb@fyslab.hut.fi) wrote: >: >: Does any (which?) handheld GPS receivers have proper temperature range >: for winter use (-45C or so)? Keeping the receiver close to the body will >: obviously keep it warm, but it will start cooling when in use. Does anyone >: have experience with handheld GPS in extreme cold? >i don;t remember the two Norwegian expedition groups which skiied to the >South Pole at the end of 1994 used special handheld GPS. i was there when >they arrived. as you said, most of the time the GPS is somewhere in the >cloths. they don;t cool down that fast when brought out. Liv used a >compass fixed infront of her to determnine direction most of the time. >the LCD display on my camera became drowsy and low-contrasty at near -40C, >but still quite readable. >- mh As you imply, the main limitation is the temperature range of LCDs. I'm surprised it worked at all at -40C - the electronics must have been keeping it a bit warmer than that! We have found that LCDs in Antarctic field situations are OK provided you can carry them inside your clothing, or you only use them in a protected environment (a tent or whatever). For use in a permanently exposed position, they are useless - the liquid freezes, which may destroy the device. It is worth noting the minimum STORAGE temperatures for the device! Unfortunately, all the alternative display devices consume far more power, which, coupled with the usual expectation that battery life will be halved at low temperatures, makes them unattractive. I can't think of a device which couples low power consumption with resistance to low ambient temperature. It would be interesting to hear from the manufacturers what their ideas are on low temperature operation. After all, temperatures below zero are commonplace over most of this planet, and temperatures below -20C are still quite usual over many densely inhabited parts of the world. Even the UK can hit -20C, though not very often. Perhaps I should note that the lowest recorded temperature (at Vostok, in Antarctica) was about -80C! Designing equipment only for operation above 0C (the norm for electronics) seems to ignore the actual range of temperatures out there. A. Paul R. Cooper British Antarctic Survey aprc@pcmail.nerc-bas.ac.uk ***** Any opinions given here are my own, ***** ***** and not necessarily those of British Antarctic Survey ***** (A P R Cooper) Message : #23140253 From: Search & Rescue Info Address : SARINFO@mindlink.bc.ca Length : 154 words Subject : Re: Handheld GPS in cold weather Org. : MIND LINK! - British Columbia, Canada Re: GPS use at low temperatures. We have found that battery life can be quite short when alkaline batteries are used in GPS's below freezing temperatures. Apparently the units use lots of power amplifying the vey weak satellite signal. Even under normal operation battery life is just a few hours under continuous operation. For Search & Rescue operations (as opposed to practises) we put new lithium baterries in the units, which gives them significantly longer life and better low temperature operation. Hope this helps, Martin Colwell. ----------------------------------------------------------------------------- Martin Colwell E-Mail Address: SARINFO@mindlink.bc.ca SAR Technology Inc. 8570 Fremlin Street (604) 325 3017 (Home) Vancouver (604) 590 7419 (Office) British Columbia (604) 590 5347 (Fax) Canada _ _ __ V6P 3X2 Making.. / \ / \ | \ \ /___\ |__// \_/ / \ | \ Smarter... ----------------------------------------------------------------------------- (Search & Rescue Info) Message : #23195260 From: Hal Lillywhite Address : hall@macs.mxim.com Length : 212 words Subject : Re: Handheld GPS in cold weather Posted: 10 Mar 1995 09:54:53 -0800 Org. : Maxim Integrated Products, Beaverton OR. In article d.wiltschko@tamu.edu (David V. Wiltschko) writes: >This is a somewhat trivial consideration next whether the unit works at >all, but in choosing a hand-held, remember that you'll probably be wearing >gloves in extemely cold weather. Actually, probably mittens! Operating a >unit with little buttons will be harder than a unit with big buttons. Actually, the size of the buttons is less important than the distance between buttons. What you want is enough room around the one you want so you don't accidently hit an adjacent button. I've seem some instruments with very small buttons which were no problem because of the spacing between buttons. Another problem is recessed vs projecting buttons. If the buttons project it will be easy for them to be accidently activated. Recessed buttons are much less likely to be hit accidently but they are a problem if you are wearing gloves. Perfection is probably not available. >It may be useful, once you've found units that work at all at these >temperatures, to test them while wearing all of your intended cold weather >gear to see how easy they are to stow and use. Definitely a good idea. (Hal Lillywhite) Sat Mar 18 09:06:44 1995 Message : #23535227 From: Markus Bjorksten Address : mfb@fyslab.hut.fi Length : 357 words Subject : Re: Handheld GPS in cold weather Martin Colwell (Search & Rescue Info) > > We have found that battery life can be quite short when > alkaline batteries are used in GPS's below freezing temperatures. > Apparaently the units use lots of power amplifying the vey weak > satellite signal. Even under normal operation battery life is just > a few hours under continuous operation. > For Search & Rescue operations (as opposed to practises) we put > new lithium baterries in the units, which gives them significantly > longer life and better low temperature operation. I think there are two basic problems with GPS in a cold environment: - Power supply. Battery life is reduced in cold weather as with all electric devices. With GPS-devices this could be circumvented if needed as with eg. head lamps using an external power source kept close to the body and connected with a cable to the device. And by using Li-batteries as Martin advices. - LCD display. This I think of as potentially the bigger problem. It could probably be circumvented by keeping the receiver close to the body when not in use. The crucial question is then whether the device will cool below operation temperature before position acquisition and whether this kind of operation is feasible in practice. I'd still be glad to get more information and experience of problems, or lack of, with GPS receivers in (extreme) cold conditions. For comparision, here is some relevant data for a few receivers all having seemingly far too high min temperature limits for winter usage: Type Min temp@ Operation time# Battery Garmin GPS 45 -15C ( 5F) 15h [25h]* 4AA Magellan Trailblazer -10C (14F) 3AA Trimble Scout + 0C (32F) 5h [15h]* 4AA @ At least for 'Trailblazer', this is due to the LCD-display. For 'Scout', this is the lower limit of "optimal temperature range". # Probably at room temperature using alcaline batteries. * In power saving mode. Start up times for 'GPS 45' are apprx. 15s (warm), 2min (cold), 7.5min (AutoLocate). Markus Bjorksten From M.Colwell SARINFO@ mindlink.bc.ca 19th March 95 From information recently receive RECHARGEABLE lithium batteries have approximately 92% of their output at 0 deg C, and 82% of their output remaining at -20 deg C, compared to approximately 30% for a rechargeable NiCad battery at -20 deg C. Rechargeable lithium batteries also have 50% greater output (watt-hours/litre) for the same volume battery, when compared to rechargeable NiCads. Moli Energy, manufacturers of rechargeable lithium batteries, are working in co-operation with Trimble Navigation, who are currently evaluating their new lithium A and AA rechargeable batteries, due to be released by this summer. As yet I have received no infomation on this evaluation, or a direct comparison of non-rechargeable lithium or alkaline batteries. Regards, Martin Colwell ----------------------------------------------------------------------------- Martin Colwell E-Mail Address: SARINFO@mindlink.bc.ca SAR Technology Inc. 8570 Fremlin Street (604) 325 3017 (Home) Vancouver (604) 590 7419 (Office) British Columbia (604) 590 5347 (Fax) Canada _ _ __ V6P 3X2 Making.. / \\ / \\ | \\ \\ /___\\ |__// \\_/ / \\ | \\ Smarter... ----------------------------------------------------------------------------- -------------------------------