GPSmap 60CSx - How to turn off the barometric altimeter?

[+LBREWSTER]

How do I turn off the built-in barometric altimeter so I can use the gps-determined altitude on the GPSmap 60CSx ??

 

(I want the actual satellite-determined altitude in an airplane cabin rather than the pressurized cabin altitude).

[+hurley_108]

How do I turn off the built-in barometric altimeter so I can use the gps-determined altitude on the GPSmap 60CSx ??

 

(I want the actual satellite-determined altitude in an airplane cabin rather than the pressurized cabin altitude).

 

Can't do it on the unit alone.

 

Only way to do it is to hook it up to a computer and read off the NMEA sentences, as those don't use the baro altimeter.

 

I really hate that - I bought a $50 higer unit expecting more, but all I got was a different way of doing altitude, one with its own pros and cons.

[Michael Cook]

You can read the GPS-determined altitude by pressing Menu on the satellite page and choosing GPS Elevation.

 

The annoyance is that you can't choose to display the GPS Elevation in a Data field: you have to go through the menu each time to see it. It would be nice if Garmin added this option in an update.

[Hertzog]

How do I turn off the built-in barometric altimeter so I can use the gps-determined altitude on the GPSmap 60CSx ??

 

(I want the actual satellite-determined altitude in an airplane cabin rather than the pressurized cabin altitude).

In addition to looking at it on the satellite page, you can mark a waypoint and then average it; when you average, the GPSr switches the elevation from the barometric value to the GPS elevation.

 

A highly undocumented method - and so far I'm the only one who has reported seeing this - is to set the Barometer Mode to "Fixed Elevation"; when you do this the 60CSx records the GPS elevation rather than the barometric elevation in the active track log and displays it in the elevation profile on the Altimeter page (but the data field values are still the barometric elevation values).

[TeamCypherX]

Aside from riding in an airplane where the pressure is constant, why would you want to turn off the barometric altimeter? Wouldn't it be more accurate overall?

[+Snoope]

These are my thoughts about the barometric altimeter. Carefully read pg.61

I went to my nearby airport, they have a national weather service automated

weather station there. It automatically transmits the info on 134.0MHZ. I listen

on a scanner, they update the pressure about every minute. On the Internet

it is updated about once an hour. They also have a surveyers elevation disk

near by. I have used both methods and they are very close, but if you answer

no to the elevation and pressure questions on the barometric setup page,

then it will give a default GPS reading, which I found to be about

30ft. different. As you know GPS elevation is not very accurate. Snoope

[+hurley_108]

Aside from riding in an airplane where the pressure is constant, why would you want to turn off the barometric altimeter? Wouldn't it be more accurate overall?

 

It's different.

 

GPS will always be close to the true altitude, but with some large error. Averaged out, the errors will cancel each other, and you can get an idea of true altitude.

 

If a barometric altimeter is properly calibrated, its error will be small and it'll give you a good altitude, but if it's calibrated badly, it will show small deviations from an altitude which is always wrong. Take it into a pressure-controlled environment and you might as well give up.

 

Thing is, the weather changes the pressure enough to screw up barometric altimetry, so you have to constantly recalibrate the altimeter, even when you're not in a plane. The unit does this for you if you tell it to, based on the altitude of the first GPS fix after powering up it seems, but this fix is always bad and so your calibration is always hopelessly screwed up, unless you know your accurate pressure, accurate elevation, or have a few minutes to average a waypoint and get a good altitude.

 

Sometimes you don't know your correct pressure because you don't carry a barometer around with you, or you don't know your correct altitude because you're out in the field trying to determine exactly that, and you don't have time to spend five minutes getting a good average waypoint. And then the weather changes over a few hours and you have to start all over again.

 

In short, barometric altitude is not better, it's different, and it's really sucky of garmin to force a different set of problems on its users who paid more for "better."

 

I bought the CSx, but I'll recommend to anyone to buy the Cx instead. It's no worse and costs less.

[TeamCypherX]

I see what you mean. I looked at the Cx as well, but I wanted the magnetic compass so I opted for the CSx instead

[NewZealand]

How do I turn off the built-in barometric altimeter so I can use the gps-determined altitude on the GPSmap 60CSx ??

 

(I want the actual satellite-determined altitude in an airplane cabin rather than the pressurized cabin altitude).

This works fine for the tracklog as described by Hertzog:

 

A highly undocumented method - and so far I'm the only one who has reported seeing this - is to set the Barometer Mode to "Fixed Elevation"; when you do this the 60CSx records the GPS elevation rather than the barometric elevation in the active track log and displays it in the elevation profile on the Altimeter page (but the data field values are still the barometric elevation values).

I recorded a flight from Paris to Vienna that way and generated a kmz-file for Google Earth from the tracklog, it looks great looking at the track in a height of 35000 feet, and seeing exactly the touchdown point at the landing and things like that.

Unfortunately there is no datafield for GPS-elevation, so if you want to see it directly during the flight, I know only the way via the satellite page, and pressing menu.

Unfortunately it's not possible to upload files here, so that I could show you the kmz-file as a sample for the correctly working GPS-elevation for the tracklog.

Edited March 12, 2007 by NewZealand