GPSMAP 64st Elevation Determination Methods

[+Team CowboyPapa]

On 3/12/2018 at 5:42 PM, Mineral2 said:

I don't have a 64, and it sounds like the barometer settings are similar but different, but on my Oregon, if I set the altimeter settings to: Auto calibration - off; and Barometer Mode - fixed elevation then the unit will record and display the GPS elevation. ......

The 64s manual does not state the same as above when Fixed Elevation is selected, from the manual.  It reads:"

"Barometer Mode

Variable Elevation allows the barometer to measure changes in elevation while you are moving. Fixed Elevation assumes the device is stationary at a fixed elevation, so the barometric pressure should only change due to weather."

https://www8.garmin.com/manuals/webhelp/gpsmap64/EN-US/GUID-3A78E778-DC5F-4F9F-BDD0-DF4C5F86B81C.html

The manual says "Fixed Elevation assumes.....", it does not say that "...selection of Fixed Elevation results in GPS derived elevations only (to the exclusion of barometric) are recorded in waypoints and tracks".

Again, nowhere in the 64s or 64st manuals is there specific, how-to, keypunch-by-keypunch, step-by-step description on how record track elevations based solely on GPS data.

 

 

 

 

 

[+Red90]

Once again, for the THIRD TIME!!!!!  I own a 64S.  I specifically went and tested the settings just for YOU.  It results in the GPS Elevation being displayed and recorded.

[+Team CowboyPapa]

19 minutes ago, Red90 said:

Once again, for the THIRD TIME!!!!!  I own a 64S.  I specifically went and tested the settings just for YOU.  It results in the GPS Elevation being displayed and recorded.

I apologize for misreading your post and not assuming that the manual failed to state that correctly and clearly..

Edited March 20, 2018 by Team CowboyPapa

[+The A-Team]

So.... have we finally reached orbit? Have you now accepted the answers you've been given, or are you still insisting on finding authoritative Garmin documentation that includes a "specific, how-to, keypunch-by-keypunch, step-by-step description on how record track elevations based solely on GPS data"?

[+Team CowboyPapa]

17 hours ago, The A-Team said:

So.... have we finally reached orbit? Have you now accepted the answers you've been given, or are you still insisting on finding authoritative Garmin documentation that includes a "specific, how-to, keypunch-by-keypunch, step-by-step description on how record track elevations based solely on GPS data"?

I don't know what other authoritative Garmin documentation there is outside of the manual which is referenced in the 2nd post above: https://www8.garmin.com/manuals/webhelp/gpsmap64/EN-US/GUID-E7105207-33CC-48F3-80D6-BBF105DFF58F.html

Please note, again, that this manual does not specify how to implement GPS only (no barometric data) elevations in recorded tracks.  Whatever Garmin source might there be?

However, looking at the manual, there are two elevation mode possibilities, Variable and Fixed, shown below from the manual in bold:

Barometer Mode

Variable Elevation allows the barometer to measure changes in elevation while you are moving. Fixed Elevation assumes the device is stationary at a fixed elevation, so the barometric pressure should only change due to weather.

Note that in engineering parlance the terms Variable and Fixed are directly opposite, or they are not synonymous and interchangeable. In this context and according to the manual description above, imposing the Fixed Elevation option will yield a constant, unchanging, barometric pressure based elevation during a track regardless of whether the actual elevation is changing or not.

Now, this inference is not in agreement with Mineral2's advice below in bold:

That is how you effectively disable the barometric altimeter with a Garmin gps. ....... But there is a homologous option.

Settings > Altimeter >
Auto Calibration > Off
Barometer Mode > Fixed Elevation

Consequently, my interpretation of Fixed Elevation is just that, Fixed and Non-Varying elevation not based on changing GPS data as the device moves up and down.

Okay, here is what I did on a walk today with my inReach, which does not record GPS data only elevations:

1.  Booted up with Auto Calibration ON and recorded every 30 seconds while walking essentially at Sea Level.

2.  Tuned Auto Calibration OFF, calibrated Altimeter to Known Elevation of 300 ft., and recorded another track while walking.

3.  Inspection of tracks back home showed the first points to be within an expected range about Sea Level and the second group about a similar range relative to 300 ft.

4.  Now, if the GPS data were to have been listed on the second track instead the barometric calibrated to 300 ft., would not the elevations (if GPS derived) be shown in the recorded track as an expected range about Sea Level?

 

As that which I would do if I had a 64s or 64st, would be somewhat similar:

1.  Walk and record a track after selecting Variable Elevation and then another after selecting Fixed Elevation.

2.  I would download both as GPX files and then open with Microsoft WordPad to inspect both.

3.  I would expect to see some data scatter in the Variable (or I may have to go up and down to impose such).

4.  If there were no GPS involvement with the Fixed option, I would expect no scatter; however, if there was pure GPS (no barometric) elevation data, I would expect to see typical scatter.

 

Outside of that, maybe the description of me above as posted by HHL is correct:

" I'm not sure of his purpose in asking here if he will not ever believe anyone....He is either rather ignorant and stupid or a Troll. Both qualifies an Ignore.""NB: I'm sorry being that harsh here. But the TO's behaviour is more than unfriendly to helpful people."

[+The A-Team]

2 hours ago, Team CowboyPapa said:

Please note, again, that this manual does not specify how to implement GPS only (no barometric data) elevations in recorded tracks.

<snipped irrelevant discussion of terminology>

Now, this inference is not in agreement with Mineral2's advice below in bold:

That is how you effectively disable the barometric altimeter with a Garmin gps. ....... But there is a homologous option.

Settings > Altimeter >
Auto Calibration > Off
Barometer Mode > Fixed Elevation

Consequently, my interpretation... <snipped more irrelevant discussion>

Okay, at this point it's become pretty clear that you have no intention of ever accepting the answers you've been given, and instead insist on receiving authoritative documentation and/or modified GPSr firmware with labels that more closely follow your personal line of thinking. Or maybe you just like arguing for the sake of arguing.

As per the two quoted posts below, you can have the device record only the GPS elevation in tracks if you use the suggested settings.

On ‎3‎/‎12‎/‎2018 at 5:42 PM, Mineral2 said:

I don't have a 64, and it sounds like the barometer settings are similar but different, but on my Oregon, if I set the altimeter settings to: Auto calibration - off; and Barometer Mode - fixed elevation then the unit will record and display the GPS elevation. I use these settings when flying and the tracks show altitudes of 35000 feet rather than the 6-8000 I would get when the barometer is set to variable.

On ‎3‎/‎14‎/‎2018 at 6:09 AM, Red90 said:

Yes, I checked Mineral2's settings and it does display and record the GPS Elevation.

You can either accept that the users here are not lying to you and have actually gone above-and-beyond by testing their suggestions in practice, or you can reject them. Either way, I think this discussion is over.

[+Team CowboyPapa]

OTOH, posting the question on the Amazon site resulted in the same answer as that above regarding the selection of Fixed Elevation: https://www.amazon.com/ask/questions/Tx1VLX1SQKW6VE8/

What truly befuddles me about that is:

1.  Nowhere in the manual does it explicitly discuss a how-to implement the GPS only option for elevation,

2.  Nor does the Fixed Elevation description mention GPS only elevations instead of barometric, it just states barometric as fixed, unchanging. 

[+Team CowboyPapa]

20 hours ago, The A-Team said:

So.... have we finally reached orbit? Have you now accepted the answers you've been given, or are you still insisting on finding authoritative Garmin documentation that includes a "specific, how-to, keypunch-by-keypunch, step-by-step description on how record track elevations based solely on GPS data"?

Yes, I have given up finding authoritative Garmin documentation; however, I would be pleasantly surprised with credible, hands-on test results.  I will admit that I will do the same in answering questions here as I prefer to respond with zero uncertainty.

[+Team CowboyPapa]

20 minutes ago, The A-Team said:

Okay, at this point it's become pretty clear that you have no intention of ever accepting the answers you've been given, and instead insist on receiving authoritative documentation and/or modified GPSr firmware with labels that more closely follow your personal line of thinking. Or maybe you just like arguing for the sake of arguing.

As per the two quoted posts below, you can have the device record only the GPS elevation in tracks if you use the suggested settings.

You can either accept that the users here are not lying to you and have actually gone above-and-beyond by testing their suggestions in practice, or you can reject them. Either way, I think this discussion is over.

1.  I am not being argumentative, I am just looking for credible answers.

2.  I have no suspicion of lying whatsoever.

[+HHL]

15 minutes ago, Team CowboyPapa said:

[...] I am just looking for credible answers.[...]

This:

 

[+The A-Team]

15 minutes ago, Team CowboyPapa said:

I am not being argumentative, I am just looking for credible answers.

In that case, you're in the wrong place. You've been given the correct answer here, but you apparently don't consider those users to be credible enough. Considering that those who provided the answer are folks who spend a lot of time answering questions in this sub-forum and are very familiar with practical GPSr usage - and therefore would be considered some of the most credible users here - you won't get anything more credible in these forums. I wish you luck in whatever platform you decide to attempt next, and sincerely hope that I don't somehow stumble into that discussion.

[+Red90]

He just likes to argue.  I can only imagine how much fun it was to work with this guy.

I've already stated multiple times that I tested it for him and somehow that is not enough.  Do we need a double blind study?  Do I need to provide my credentials?  Would you like a report and letter with my engineering stamp on it?  Screenshots on each step to change the settings with all of the results?  Fly to your house, hold your hand and push the buttons for you?

[+Team CowboyPapa]

My most humble and heartfelt apologies.

[+Mineral2]

1 hour ago, Team CowboyPapa said:

OTOH, posting the question on the Amazon site resulted in the same answer as that above regarding the selection of Fixed Elevation: https://www.amazon.com/ask/questions/Tx1VLX1SQKW6VE8/ 

Did you not put two and two together?

[+Team CowboyPapa]

2 hours ago, Mineral2 said:

Did you not put two and two together?

YUUUP! As I type!!

[+Team CowboyPapa]

On 3/12/2018 at 5:42 PM, Mineral2 said:

I don't have a 64, and it sounds like the barometer settings are similar but different, but on my Oregon, if I set the altimeter settings to: Auto calibration - off; and Barometer Mode - fixed elevation then the unit will record and display the GPS elevation. I use these settings when flying and the tracks show altitudes of 35000 feet rather than the 6-8000 I would get when the barometer is set to variable.

If it shows altitudes greater than 8,000 feet as you climb to a cruising altitude of 35,000 ft., then they must by GPS sourced as opposed to Barometric sourced where they would stay at or below 8,000 ft.

[+Atlas Cached]

4 hours ago, Team CowboyPapa said:

If it shows altitudes greater than 8,000 feet as you climb to a cruising altitude of 35,000 ft., then they must by GPS sourced as opposed to Barometric sourced where they would stay at or below 8,000 ft.

Precisely what others have been telling you.

 

Like some of them, I have used my Garmin GPSr to track flights, and the only way to get correct altitude (it's not elevation unless you are standing on the ground) readings is to set any of my Garmin GPSr to "Barometer Mode > Fixed Elevation" and set the auto calibration off. 

Now, when the Garmin GPSr is in this mode, where it is NOT using the atmospheric pressure to calculate elevation, the unit CAN be used as a portable weather station to assist in predicting the weather, so long as it is also set to collect barometer readings even when powered off.

See Applications > Elevation Plot > Weather Station. for an example.

[+Team CowboyPapa]

On 3/21/2018 at 10:27 AM, Team CowboyPapa said:

Fixed Elevation assumes the device is stationary at a fixed elevation, so the barometric pressure should only change due to weather.

OK, the quote above is from the manual.  As I have stated above, I feel that the omission of GPS sourced elevations in that statement from the manual is an error.  I would have written it to include that when selecting the Fixed Elevation option, "elevations recorded for waypoints and tracks are GPS sourced".

However, now that I accept that they are GPS derived, I see another supporting reason in addition to values greater than 8,000 ft while flying.

That is, assuming it is true that the elevations fixed after selecting the Fixed Elevation option are Barometric elevations, then those that vary at any elevations must by GPS derived.

[+Team CowboyPapa]

@Mineral2

I thank you very much for the suggestion above. I now have a GPSMAP 66i, and tested with the settings you provided. Prior to the test, I modified the Trip Computer page: (1) I retained “Elevation” in the upper most left column slot, (2) I replaced the next slot down with “GPS Elevatiom, (3) I replaced the upper most right column slot with “Barometer”, and (4) I replaced the next slot down with “Ambient Press.”.

I then changed the Auto Calibration to “Off” and the Barometer Mode to “Fixed Elevation”. Additionally, I manually selected the Calibrate Altimeter Method of Current Elevation to Calibrate to 200 ft.

 

Walking along the level Green Belt (about 100 yards off the shore) in Sunset Beach, CA, I recorded about a ½ mile track. As I walked the Elevation slot displayed a constant value of 200 ft. while the GPS Elevation slot displayed between 9 ft. and 15 ft., which was reasonable. After concluding the walk, I synced to the Explore app on my phone and viewed the elevation profile as a constant 200 ft. Conclusion, these Altitude settings resulted in the barometric elevations being recorded and not the GPS derived elevations.

 

My next test was to set the Auto Calibration to “Continuous” and the Barometer Mode to “Variable Elevation”.Additionally, I manually selected the Calibrate Altimeter Method of GPS Altitude and selected “Calibrate”.

I then drove up and down a hill, while not recording a track, of about 50 feet and noticed that the Elevation and GPS values were identical. Now, selecting “Start” to record the track, I noticed that the values for Elevation and GPS Elevation varied by a few feet, with the Elevation being a few feet higher than the GPS Elevation values/ Actually, they both decreased going down the hill and increased going up. On basically a level street, they both went up and down slightly, with the Elevation values always slightly higher than the GPS Elevation values.

 

Conclusion: Referring back to the top, with the two top fields, on the left, being Elevation above GPS Elevation, it is the top most, Elevation values that always are recorded. When Altitude calibrated to GPS and Continous selected, the top most value is GPS. However, when not recording, both fields are identical while there are slight differences when recording.

[robertlipe]

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