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Altitude struggles, GPS errors nearing the Summit

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10/14/2010 10:48 PM EDT

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DWenn
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re: Altitude struggles, GPS errors nearing the Summit
DWenn   10/24/2010 3:56:36 PM
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Good points on the GPS. As I said I think it was struggling because we only gave it 45 seconds to find a lock before going back to sleep. Now this was okay once we were on the mountain and walking normally but it obviously gave problems on the first few days. Really this is down to 'operator error', one of the more common causes of failure in electronic equipment! :-) Chris put his batteries in when in Africa and his unit started tracking correctly iummediately. Whereas I wanted to try and record the pressure changes during the flight down to Africa so I put my batteries in before flying hence causing the problem.... DOH! But at least it did catch up. One thing I would do in retrospect would be to add a 'Sample Now' button allowing the user to force a reading at any time.

Darius Pl.
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re: Altitude struggles, GPS errors nearing the Summit
Darius Pl.   10/24/2010 11:33:32 AM
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GPS unit based on almanac (satellite navigation data), its last known location and current time and date initiates signal search first for satellite signals that should be visible to it for given location and time (about 8 to 12 signals), plus it can compute the expected Doppler values of the signals to reduce the search space. If this fails then the GPS unit starts to look for the rest of signals out of 32 possible. When you move more than a couple thousands of kilometers the expected signal list will not match the actual situation at the new location - the older generation GPS units will spend quite some time to find the GPS signals.

Darius Pl.
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re: Altitude struggles, GPS errors nearing the Summit
Darius Pl.   10/24/2010 11:25:00 AM
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Yes, a bit more new GPS unit would help. They have many more HW resources to acquire GPS signals as consequence of design for a high sensitivity. You are right about GPS data rate, but if there are signal obstructions then the GPS signals will be even more week - data errors will require repeated reception(s) of data frames. If you can enter manually an approximate current position into your GPS unit, then this should help its acquisition process to find much faster the correct set and the correct parameters for satellite signal. Today you can by a dedicated GPS unit (consumer class) with an inbuilt barometer. That should give you quite precise elevation.

Phil16v
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re: Altitude struggles, GPS errors nearing the Summit
Phil16v   10/22/2010 12:25:17 AM
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Are you sure the southern hemisphere uses different satellites? I thought that most of the satellite constellation passed over both hemispheres.

selinz
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re: Altitude struggles, GPS errors nearing the Summit
selinz   10/21/2010 3:19:20 PM
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I've had a Garmin Palm based PDA for many years (definitley getting long in the tooth) but it still is quite a bit more accurate than my HTC cell phone GPS. This is particularly true in elevation. I work and live at about sea level and when I first turn on my phone, it shows -200 ft elevation. It eventually gets close. The Garmin is slower but more accurate. And yes, when I hop off of a plane in Japan or Europe, the Garmin takes significantly longer to find itself...

t.alex
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re: Altitude struggles, GPS errors nearing the Summit
t.alex   10/17/2010 2:05:59 AM
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The first 2 days data was not correct! that's a big deal.

Etmax
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re: Altitude struggles, GPS errors nearing the Summit
Etmax   10/16/2010 7:22:16 AM
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Yeah why is it that no one links electrolyte balance with dehydration?

Jack.L
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re: Altitude struggles, GPS errors nearing the Summit
Jack.L   10/15/2010 3:58:05 PM
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Watch you do not go too crazy on the water or you will lose too many eletrolytes.

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