Lack of elevation calibration in the receiver

[Nail]

I have a problem with calibrating the altimeter in GPSMAP 67. The receiver does not want to change the altitude above sea level to the current one. Calibration is set to once, even when I change it to continuous, in no way does altitude calibrate to GPS values during activity. I have a question, can you check if your GPSMAP 67 or 66sr receivers are changing the altitude to the correct one? (Fv 8.30)

(I asked this question in another topic, but the scope of the topic may have made it less frequently visited.)

[mimichris]

My 67 is configured as follows:
Auto calibration: once
Barometer mode: variable altitude
pressure trend: record when on
type of route: altitude distance

With this configuration, I always have the right altitude from the place to the ignition of the 67.

[Nail]

My 67 is configured as follows:
Auto calibration: once
Barometer mode: variable altitude
pressure trend: record when on
type of route: altitude distance

With this configuration, I always have the right altitude from the place to the ignition of the 67.

I have the same settings.
I have a request: enter the elevation manually, e.g. "0m" (or feet depending on what units you use) and calibrate. Then start recording and check if the altimeter has changed the elevation?
In my opinion, you will not see the correct height and it will still be "0m".

Of course, if you are currently at elevation 0m, it will actually be fine. In this case, calibrate a different elevation, e.g. "999m"

[Nail]

I couldn't edit the message anymore, correction to the previous post. Bold text
I added an image of how I do it and what the effect is.
The moderator may delete the previous entry.

My 67 is configured as follows:
Auto calibration: once
Barometer mode: variable altitude
pressure trend: record when on
type of route: altitude distance

With this configuration, I always have the right altitude from the place to the ignition of the 67.

I have the same settings.
I have a request: enter the elevation manually, e.g. "0m" (or feet depending on what units you use) and perform calibration. Then start recording, disable, delete or save the file and check if the altimeter has changed elevation?
In my opinion, you will not see the correct height and it will still be "0m".

Of course, if you are currently at elevation 0m, it will actually be fine. In this case, calibrate a different elevation, e.g. "999m"

Spoiler

Elevation.jpg

[Manu]

I own the following devices: Map 60 csx, Map 65s, Map 66sr, Map 67i and Tactix 7

The Map 65s is the device that works best overall: accurate track register, precise and consistent altimeter as well as the compass.

In the map 65s the total ascent/descent data are adherent to reality.

If I start a walking path from an altitude of 350 meters and arrive at 700 meters, the device must indicate a total ascent of about 350 meters.

Or if I walk flat for a few km the total ascent/descent must be a few meters.

This behavior always occurs with map 65s.

With map 66sr and 67i I always have total ascent/descent values more than 50% higher than in reality.

I think that the 66sr and the 67 have two distinct problems: the first is that the total ascent/descent calculation considers only the barometer data.

The second problem is the position of the barometric sensor whose hole is exposed at the rear of the device (in the map 65s this hole is inside the battery compartment being more protected and correctly measuring the pressure)

In the Tactix, to keep the total ascent/descent data adherent to reality, Garmin technicians have introduced an automatic mode for the operation of the altimeter (not present in portable devices).

I think it is needed for accurate measurements of the difference in height .. important for example for those who do running races in the mountains ..

In the Tactix the total ascent/descent data is perfect and superimposed on those of the 65s map.

I believe that Garmin technicians know about the total ascent/descent problem that persists on maps 66sr and 67 and I don't understand why it is not possible to remedy it.

Then in the map 67 with the latest firmware version 8.30 came to create a fluctuation of the position when the device is stopped .. 10, 20 and even 30 meters ..

Amen..

[Nail]

I own the following devices: Map 60 csx, Map 65s, Map 66sr, Map 67i and Tactix 7

Then in the map 67 with the latest firmware version 8.30 came to create a fluctuation of the position when the device is stopped .. 10, 20 and even 30 meters ..

Amen..

I don't notice a problem with large differences in the length of descent/entry compared to reality. I checked all historical GPS traces and I have no such discrepancies. I always prudently turn on the receiver in advance so that something doesn't surprise me at the beginning of the hike. Maybe that's why I don't see the differences. Of course it shouldn't be like this. The device should function properly immediately after startup.

I see a problem with GPSMAP67, which changes position when stationary, it happened before, but before 8.30 I didn't have this problem anymore. Now it's back.

Coming back to the problem I noticed was the lack of altitude calibration. If you have a moment, check out the following procedure in your 67 receiver: Manually change the elevation to a completely different one than the one you are on. Calibration setting at once. Wait until "Elevation GPS" stabilizes (fixes). Start activity recording. Turn off recording, you can delete or save permanently, it doesn't matter. "Elevation" should now calibrate itself. Turn the receiver off and on and you should see "elevation" in the field that matches the previous "elevation GPS". Is that so? You can also compare how it works in GPS-65. Thank you for your answer.

[mimichris]

That's what I have, I'm at 108m altitude and each time I start the GPS once the satellites have been acquired, I find my 108m, if I'm hiking and I go home, I turn the 67 back on, I'm again at 108m, no problem for me, version 8.30.
If I change location, the altitude of the place is displayed, and to be sure I have the right altitude, I look at the nearby altitudes indicated on the map which are accurate to within +/-5m from the IGN DEMs of France.

[Nail]

That's what I have, I'm at 108m altitude and each time I start the GPS once the satellites have been acquired, I find my 108m, if I'm hiking and I go home, I turn the 67 back on, I'm again at 108m, no problem for me, version 8.30.
If I change location, the altitude of the place is displayed, and to be sure I have the right altitude, I look at the nearby altitudes indicated on the map which are accurate to within +/-5m from the IGN DEMs of France.

So enter 0m and see if it corrects to an elevation of 108m? You describe the operation of a barometric altimeter. The barometric altimeter also works well for me. We have two altitudes, "GPS elevation" and elevation from the barometric altimeter. If you have calibration set, the barometric altimeter must calibrate when activity recording is turned on. I believe that the barometric altimeter does not calibrate to "Elevation GPS". Please check.

[Manu]

I don't notice a problem with large differences in the length of descent/entry compared to reality. I checked all historical GPS traces and I have no such discrepancies. I always prudently turn on the receiver in advance so that something doesn't surprise me at the beginning of the hike. Maybe that's why I don't see the differences. Of course it shouldn't be like this. The device should function properly immediately after startup.

I see a problem with GPSMAP67, which changes position when stationary, it happened before, but before 8.30 I didn't have this problem anymore. Now it's back.

Coming back to the problem I noticed was the lack of altitude calibration. If you have a moment, check out the following procedure in your 67 receiver: Manually change the elevation to a completely different one than the one you are on. Calibration setting at once. Wait until "Elevation GPS" stabilizes (fixes). Start activity recording. Turn off recording, you can delete or save permanently, it doesn't matter. "Elevation" should now calibrate itself. Turn the receiver off and on and you should see "elevation" in the field that matches the previous "elevation GPS". Is that so? You can also compare how it works in GPS-65. Thank you for your answer.

I did the test you described.

The Map67 also behaves as you say; that is, it does not self-calibrate.

But if for example I move to a higher effective quota and repeat the test the Map 67 performs the self-calibration.

You can't understand the logic with which you self-calibrate the altimeter.

Among other things, the altimeter settings you suggested are the factory ones.

However, at every turn I carry out a manual calibration to correct igm dimensions.

But I would like to focus on the issue raised in my previous message.

I set up my Map66 and Map67 so that they show two data fields: full ascent and total descent.

The values shown by these data fields must realistically show the ascent and descent in meters that the device has made up to that point.

The current quota is always accurate.

What's wrong with the 66 and 67 is the calculation of ascent and descent!

If you don't set these data fields with full ascent and total descent you probably can't see the problem.

I make fairly long walks or rides in the mountains.

Accurate ascent/descent data is important to me.

[JungleJim]

I also did the tst

I have a request: enter the elevation manually, e.g. "0m" (or feet depending on what units you use) and perform calibration. Then start recording, disable, delete or save the file and check if the altimeter has changed elevation?
In my opinion, you will not see the correct height and it will still be "0m".

So I tried this at well. When calibrating manually and entering an elevation that is not correct for the current position, the elevation reported by my GPSMAP 67 (via data field) does not change when starting activity recording. I did a manual calibration before the device had a GNSS fix and therefore did not have a value for the GPS elevation.

But honestly I'm not really sure how this is supposed to work. Based on my experience with Auto Calibration set to Once, the device will calibrate the elevation to GPS elevation after having been turned on and getting a GNSS fix. So not after starting activity recording, but this may simply be an error in the manual (because default configuration is that recording automatically starts).

Maybe the GPSMAP simply starts in an uncalibrated state. With Auto Calibration set to Once, the device calibrates itself to GPS elevation after getting a fix and changes to calibrated state. Or the user calibrates elevation manually, in which case the device also becomes calibrated. Continous Auto Calibration just expands on this by periodically recalibrating to GPS elevation.