Garmin 60CSx showing incorrect altitude

[Peakbagr]

My 7 year old otherwise very accurate Garmin 60CSx has been showing inaccurate altitude numbers. I've noticed it the last 18 months so it may have been going on longer.
When the unit was less than a year old it was having difficulty 'finding' satellites when used on consecutive hikes in widely separated locations. It was suggested that the unit needed to get a long look at the sky and I should leave it on for a few hours in a location with a wide view of the sky. That cured the problem.

Could the altitude inaccuracy be caused by not my setting the elevation at a known point at the beginning of a hike, or the compass not being recalibrated after a battery change? I used to recalibrate the compass before every 'whack but fell out of that habit.

Thanks,
Alan

 

[DougPaul]

The 60CSx (and all Garmin GPSes with "sensors") has a barometric altimeter. As with all barometric altimeters, the accuracy depends upon proper calibration. The easy way is to set them to automatic calibration which uses the GPS altitude to calibrate the barometric altimeter. In my experience, the altitudes are pretty accurate after an hour or so of continuous operation. (The automatic calibration takes a while.)

GPSes without barometric sensors can only output the GPS altitude which has a nominal accuracy of 95% probability of being within ~20 meters.

Doug

 

[jniehof]

Might be worth looking for the "altimeter hole." Don't know where it is on the 60CSx, but if that gets clogged up (the usual culprit on the wrist models is sweat/salt, for yours I'm guessing spruce bits from bushwhacking), the air can't get to the actual pressure sensor and everything will be out of whack. Clean it very gently with a toothpick or needle (don't go poking in too far). I think the waterproofing is sufficient for a quick rinse-off, but I won't buy you another if it isn't

 

[DougPaul]

Might be worth looking for the "altimeter hole." Don't know where it is on the 60CSx,

The altimeter hole is the four small holes in the upper back of the case.

When I shine a light in the holes, there is something visible (an air-permeable membrane?) on the inside surface of the case covering the holes. I would be very careful not to poke a hole in it--such a hole would probably allow dirt into the interior of the sensor or case.

Clean it very gently with a toothpick or needle (don't go poking in too far). I think the waterproofing is sufficient for a quick rinse-off, but I won't buy you another if it isn't.

I'd try a bit of adhesive tape across the back to try to pull the dirt out. The 60CSx is rated for a 30 minute 1 meter deep immersion so it should be able to withstand a gentle rinsing. (Remove the batteries and dry it thoroughly before reinstalling the batteries.)

Doug

FWIW, I carry my 60CSx in a Garmin case and there is no visible dirt.

Doug

 

[Peakbagr]

I've blown into the holes and going to try tape next. I too use a Garmin GPS case on the pack strap but have left the top open for quicker access.
Is automatic calibration in one of the easy to find menus and if set, does setting the elevation at a give location override it?

 

[bikehikeskifish]

You have three choices

1. Use GPS Elevation
2. Enter known atmospheric pressure
3. Enter known elevation (such as at your house or the trailhead)

The option is right on the Altimeter screen under Menu...Calibrate Altimeter.

Tim

 

[DougPaul]

I've blown into the holes and going to try tape next. I too use a Garmin GPS case on the pack strap but have left the top open for quicker access.

If blowing on the holes changes the altitude reading, they are not blocked. (Hold the GPS in front of a mirror so you can read it while blowing on the back.) Also if you can see the membrane on the inside of the case the holes are also unlikely to be blocked. I wouldn't poke anything inside the holes except as a last resort.

Is automatic calibration in one of the easy to find menus and if set, does setting the elevation at a give location override it?

main_menu>setup>altimeter

You can still initialize the altimeter to the current pressure/altitude/gps_altitude to reduce the automatic calibration time. (from the altimeter screen: menu> calibrate_altimeter>)

I generally just leave the GPS on while driving to the trailhead (3hrs for the Whites--1 hr should be enough). The (auto) calibration is fine when I get there. I just swap in a fresh set of batteries and hit the trail. Or you can just turn the GPS on at the trailhead and the calibration should be fine by the time you reach the summit (again, anything over an hour should be ok).

Doug

 

[bikehikeskifish]

If blowing on the holes changes the altitude reading, they are not blocked. (Hold the GPS in front of a mirror so you can read it while blowing on the back.)

Put it in a gallon zip lock bag, seal it up, and squeeze the bag. You'll descent at an alarming rate!

Tim

 

[Peakbagr]

Thank you folks