tnle2 Posted May 21, 2008 Share Posted May 21, 2008 (edited) Hi, I did a search but couldn't find an answer to this. Are you suppose to recalibrate the altimeter each time you turn the GPS off and back on again? I went on a hike the other day to the top of a 5600' peak mountain. At that point I turned the GPS off. When I got home I turned it back on and it still says 5600' elevation even though my home is at an elevation of 700'. I have the altimeter settings to the default: Auto Calibration ON and Variable Elevation. Is there something else I'm missing? My old GPSMAP 60CS didn't exhibit this behavior, but I read it keeps track of the barometric pressure even when the unit is turned off. Does that have something to do with it since I assume the HCx does not do this? Thanks, Tim Edited May 21, 2008 by tnle2 Quote Link to comment
Rhialto Posted May 21, 2008 Share Posted May 21, 2008 Never calibrated mine and I checked it once when I saw a sign on a road telling the current altitude and it was spot on. I never really used it after that but I see the atitude sometimes when travelling and it seems on the accurate side. Quote Link to comment
Hertzog Posted May 21, 2008 Share Posted May 21, 2008 Hi, I did a search but couldn't find an answer to this. Are you suppose to recalibrate the altimeter each time you turn the GPS off and back on again? I went on a hike the other day to the top of a 5600' peak mountain. At that point I turned the GPS off. When I got home I turned it back on and it still says 5600' elevation even though my home is at an elevation of 700'. I have the altimeter settings to the default: Auto Calibration ON and Variable Elevation. Is there something else I'm missing? My old GPSMAP 60CS didn't exhibit this behavior, but I read it keeps track of the barometric pressure even when the unit is turned off. Does that have something to do with it since I assume the HCx does not do this? Thanks, Tim That doesn't sound like normal operation; although they have possibly made some changes to the software algorithms, it should still work basically the same as the 60CS. I wonder if the vent hole for the altimeter has somehow gotten plugged up. As a sanity check look at the ambient pressure to see if it is consisent with being back at 700 feet, or if it is still reading 5600 feet pressures. Quote Link to comment
+julianh Posted May 21, 2008 Share Posted May 21, 2008 Hi, I did a search but couldn't find an answer to this. Are you suppose to recalibrate the altimeter each time you turn the GPS off and back on again? I went on a hike the other day to the top of a 5600' peak mountain. At that point I turned the GPS off. When I got home I turned it back on and it still says 5600' elevation even though my home is at an elevation of 700'. I have the altimeter settings to the default: Auto Calibration ON and Variable Elevation. Is there something else I'm missing? My old GPSMAP 60CS didn't exhibit this behavior, but I read it keeps track of the barometric pressure even when the unit is turned off. Does that have something to do with it since I assume the HCx does not do this? Thanks, Tim Your settings all sound right. I can only assume that your GPSr is one of the units that does not log barometer pressure even when turned off (some do, some don't) or else, if it is capable of logging barometric pressure when off, you have not activated the function. (This is user-selectable - you have to set it to record barometric pressure even when turned off, and of course, this mean your unit will still be consuming some battery power when turned off.) If so, when you turned it back on, it just started off assuming that your elevation was unchanged since the last time it had a reading. I'll bet that if you had left it turned on during your descent, it would have been close to spot on when you got back home. Also, even with the big starting error, it should self-correct when turned back on, although it can take half an hour to an hour of auto-calibration to iron out an initial mis-calibration of this magnitude. Hope this helps! Quote Link to comment
EFIALTIS Posted July 9, 2008 Share Posted July 9, 2008 ....."And the altimeter problem seems to happen because the HCX units don't measure pressure while off. All the previous units like the 60csx measured even while off (at a low battery cost) and this is vital if you want to have continuous readings without calibrating all the time. (this happens for example with my casio altimeter wrist watch) So i don't understand why Garmin changed the altimeter algorithm It seems that Garmin (the supposed Leader blah blah ....) really messed things up and they don't do anything about it We are just the suckers who bought their precious little machines".... Quote Link to comment
+DENelson83 Posted July 9, 2008 Share Posted July 9, 2008 (edited) The 60CSx with its S★III receiver does not have that pressure-trend recording feature. My 76CSx doesn't have it either, but that's okay since I live near a surveyed location with a known surveyed elevation above sea level. Edited July 9, 2008 by DENelson83 Quote Link to comment
EFIALTIS Posted July 9, 2008 Share Posted July 9, 2008 The 60CSx with its S★III receiver does not have that pressure-trend recording feature. My 76CSx doesn't have it either, but that's okay since I live near a surveyed location with a known surveyed elevation above sea level. Yes sorry the Vista C is the unit that recorded pressure while turned off... Quote Link to comment
EFIALTIS Posted July 9, 2008 Share Posted July 9, 2008 The 60CSx with its S★III receiver does not have that pressure-trend recording feature. My 76CSx doesn't have it either, but that's okay since I live near a surveyed location with a known surveyed elevation above sea level. Yes sorry the Vista C is the unit that recorded pressure while turned off... Quote Link to comment
sokolo0 Posted July 9, 2008 Share Posted July 9, 2008 You can perform similar test everywhere. Climbing mountain is not necessary. If you are at 100mtr above sea level, and you calibrate GPSr - say - as 444mtr above sea level, GPSr will keep that altitude (or near this) to the end of this day. The same with Colorado. Auto calibration works only when you set realistic elevation ( error less than 100mtr). Recalibration is necessary after significant change of elevation. Colorado - after such false calibration: return to reality next day: 60CSx - false calibrated : normalisation - next day: Christopher Quote Link to comment
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