GPSrChive Discussion Forum

Recently I got my GPSMAP 66s from ebay for use on my electric scooter, and everything related to GPS is working perfectly. no problems here. It acquires GPS faster than all of my garmin devices, and very versatile. Except one problem.

I've used lots of Garmin devices. Garmin Edge 810 installed on my bike, and wear Garmin Fenix 5s plus everyday. These units' barometic altimeter is great. Grade data resolution is 0.1% on uphill, and most importantly, smooth. On my Fenix, refresh rate of grade data is incredibly fast. Foretrex 601 was not that responsive, but still it does display right value whenever I move or stay still.

On the other hand, GPSMAP 66's Barometic altimeter itself is working properly, and shows uphill and downhill on the map. But It doesn't seems to be accurate and responsive as other units. Grade datafield is sluggish and shows inaccurate data. Sometimes grade displays 'inf' and refuses to work. Sometimes vertical speed data shows random value when i stay still. It displays reasonable data when I move vertically, so sensor itself is not defective.

Random value problem can be caused by a pressure change, but I wonder why GPSMAP 66 altimeter is worse than Edge or Fenix. There shouldn't be any reason for it. Are they using cheaper baro sensor? GPSMAP is one of the flagship handheld from Garmin, so they should not use inexpensive chip. If It's not chip problem, then why it becomes less accurate and sluggish than other cheaper units?

Even 20 years old Etrex Vista did great on vertical speed. Vista updated vertical speed frequently at 1Hz refresh rate. I hope my GPSMAP 66s displays accurate VS and grade so that I can measure battery usage on my Escooter. Uphill requires more energy, you know.

Thanks in advance.

The GPSMAP 66 is a great handheld GPSr.

With regard to your elevation issue with this device, please reference Barometric Pressure and Altimeters.

What firmware version is your GPSMAP 66 currently running? (Setup > About)

Also, consider that the unit was used when you received it, and the previous owner may have done some strange things when it came to 'manually calibrating the altimeter', so may I suggest performing the Master Reset shown below to restore all settings to default values, and then test again?

Make sure you backup any important data on your GPSMAP 66 first.

How do I Master Reset my GPSMAP 66?

1. Power the GPSMAP 66 off.
2. Press and hold the (Page) and (Enter) buttons simultaneously.
3. Press and release the (Power) button.
4. The GPSMAP 66 will begin the boot process.
5. Release the (Page) and (Enter) buttons after the backlight illuminates.
6. When prompted "Erase all user data?", select [Erase].


Please update us after testing again!

Hi.
I think there is a much slower barometric pressure reader in the 66 than in etrex vista or some other units.
While i still had my vista hcx (before it broke) i took the 66st and the vista side by side in the car sometimes.
On one particular long stretch of downhill road it became very obvious that the 66st is lagging a lot if the pressure changes a lot over a short period of time.
After i had reached the bottom and started to go up again, the vista was spot on, the 66st still shows that the elevation is going down even as i started moving up again.

Note also that there is no jump-start menu on the 66st, i think the chip is different and slower, it has nothing to do with the settings as far as i can tell.