Jump to content

Vista Cx Barometer


Mearth

Recommended Posts

I turned a buddy onto the use of a GPS while kayaking. I showed him how to use my Legend on day one and didn't get it back until the end of the week. So, of course, he has to go out and buy a unit that's LOTS better than mine. He's intrigued by the barometer function of the Cx, but since it seems to be a new addition, I wonder how well it works and how user-friendly it is. Any feedback for him?

Link to comment

Barometers in GPS units have been around for years. I have never found the use for one. They will report altitude more accurately than a non-barometer unit, if, and only if, they are properly calibrated. They must be calibrated often. You have to calibrate them against a known altitude or a known barometric pressure to have good accuracy. A regular GPS will give you altitude readings that are pretty darn accurate. Besides...Who really cares? I mean, you are where you are. Who cares if you really are at 7580 feet instead of 7500 as reported by your regular old non-barometer GPS? Some will claim they use it to predict weather...Watching the barometer climb or dive over several hours. I tend to rely on the TV or Radio for my weather predictions. They are more accurate than me guessing about it based on my GPS. The other thing they will do is track your elevation gain/loss over a time period. My legs will tell me that data!

Link to comment

I assume you meant the barometric altimeter. I have two units with the barometric altimeter, a Vista and a 60CS. I can't think of a time it was ever useful to me. I even have the altimeter screen suppressed on my 60CS and would on my Vista if I knew how.

 

As the previous poster mentioned, they require frequent calibration. you generally already need to know your altitude to calibrate it. I do this buy calibrating it when I cross a contour line on the topo map. At least I used to. Because I rarely use the altimeter I haven't calibrated it in nearly a year.

Link to comment

I found the previous responses interesting, since I use the barometric altimeter quite a bit on my Vista Cx.

 

Perhaps its just a factor of what you use your GPSr for the most. For me, it's hiking, backpacking and photography. I like being able to glance at my GPSr and know my altitude as well as my location. I can do this without having to squint at a contour line, and/or count in between labeled contours on the topo.

 

You just need to be aware of the limitations of barometric altimeters, as mentioned above (frequent calibration, especially during changing weather). I usually calibrate the altimeter during rest stops. It take about 15 seconds.

 

I don't use the barometer for weather forecasting.

Link to comment
A regular GPS will give you altitude readings that are pretty darn accurate. Besides...Who really cares? I mean, you are where you are. Who cares if you really are at 7580 feet instead of 7500 as reported by your regular old non-barometer GPS?

 

Well, a sky diver would! :laughing: Interestingly, my Vista comes with a Jumpmaster program used by skydivers where knowing your altitude using the barometric readings is really important. The satellite data would not be accurate or reliable enough. I suppose hang gliders, soarers and others like them would find the barometric altimeter a real plus as well.

 

If you're tracking your elevation to report tracking later on for hiking or trail info to share with others, the barometric readings continue even during the times you lose the sats. It's more accurate as well.

 

Also, people have mentioned that using it for weather prediction is handy too.

 

Like bells and whistles on any kind of equipment, no one uses them all. But if you have a use for it, or might in the future, it's there.

Edited by Alan2
Link to comment
A regular GPS will give you altitude readings that are pretty darn accurate. Besides...Who really cares? I mean, you are where you are. Who cares if you really are at 7580 feet instead of 7500 as reported by your regular old non-barometer GPS?

 

Well, a sky diver would! :laughing: Interestingly, my Vista comes with a Jumpmaster program used by skydivers where knowing your altitude using the barometric readings is really important. The satellite data would not be accurate or reliable enough. I suppose hang gliders, soarers and others like them would find the barometric altimeter a real plus as well.

 

If you're tracking your elevation to report tracking later on for hiking or trail info to share with others, the barometric readings continue even during the times you lose the sats. It's more accurate as well.

 

Also, people have mentioned that using it for weather prediction is handy too.

 

Like bells and whistles on any kind of equipment, no one uses them all. But if you have a use for it, or might in the future, it's there.

 

On my map76scx, why when i try to calibrate the barometer by local weather settings, say 28.89mb, when I clik ok it goes to say 1013.1 mb, same as abient pressure ?

Link to comment

On my map76scx, why when i try to calibrate the barometer by local weather settings, say 28.89mb, when I clik ok it goes to say 1013.1 mb, same as abient pressure ?

If your local pressure is really 28.89 mbar then you better have a space suit and oxygen supply handy since that's not nearly enough to sustain life. You probably mean that the local pressure is 28.89 inches of mercury ("Hg), which would be equivalent to 978.3 mbar.

 

I presume your 76CSx is refusing to accept the 28.89 value since it's way outside the normal range. Can you change the units to accept values in inches of Hg instead of millibars?

 

With regard to calibration, the Vista and 60/76CS/x models can be set to automatically calibrate the barometer sensor using time-averaged GPS readings. This won't be quite as accurate as frequent manual recalibration if you can do so at places of precisely known altitude, but will still be much more accurate than using a GPS without any barometric sensor. The altitude values using this convenient automatic calibration should still be more accurate than the contour lines on the 1:100,000 scale USGS maps used by Garmin's USTopo maps. So I certainly wouldn't use crossing of the contour lines on those maps to do manual recalibrations.

Edited by peter
Link to comment
With regard to calibration, the Vista and 60/76CS/x models can be set to automatically calibrate the barometer sensor using time-averaged GPS readings.

 

Reading the manual for the 60CSx, seems like this is the default method and is used unless the unit is manually calibrated. If you manually calibrate the unit, how long does the calibration last, til the unit is turned off?

 

Also, since most of the time I would use the altimeter is while towing to determine the road grade, would using the elevation signs at overlook be better for manually calibrating or just leaving at the default?

Link to comment
With regard to calibration, the Vista and 60/76CS/x models can be set to automatically calibrate the barometer sensor using time-averaged GPS readings.

 

Reading the manual for the 60CSx, seems like this is the default method and is used unless the unit is manually calibrated. If you manually calibrate the unit, how long does the calibration last, til the unit is turned off?

 

Also, since most of the time I would use the altimeter is while towing to determine the road grade, would using the elevation signs at overlook be better for manually calibrating or just leaving at the default?

 

On the 76, it has 1011mb for abient pressure as well as barometric pressure. And when I try to change pressure to local readings, like 29.50 etc, it doesn't stick and goes back to whats being read??????

Link to comment
With regard to calibration, the Vista and 60/76CS/x models can be set to automatically calibrate the barometer sensor using time-averaged GPS readings.

 

Reading the manual for the 60CSx, seems like this is the default method and is used unless the unit is manually calibrated. If you manually calibrate the unit, how long does the calibration last, til the unit is turned off?

 

Also, since most of the time I would use the altimeter is while towing to determine the road grade, would using the elevation signs at overlook be better for manually calibrating or just leaving at the default?

 

On the 76, it has 1011mb for abient pressure as well as barometric pressure. And when I try to change pressure to local readings, like 29.50 etc, it doesn't stick and goes back to whats being read??????

 

Peter, I changed the measurements as you suggested and that fixed the problem, thanks a bunch.

Link to comment
With regard to calibration, the Vista and 60/76CS/x models can be set to automatically calibrate the barometer sensor using time-averaged GPS readings.

 

Reading the manual for the 60CSx, seems like this is the default method and is used unless the unit is manually calibrated. If you manually calibrate the unit, how long does the calibration last, til the unit is turned off?

 

Also, since most of the time I would use the altimeter is while towing to determine the road grade, would using the elevation signs at overlook be better for manually calibrating or just leaving at the default?

1) Depends on how you have the "Altimeter Setup" arranged from the Main Menu page. If "Auto Calibration" is turned off, then the unit will use your manual calibration as the starting point and determine elevations based on pressure changes from that time on until you again do a manual recalibration. OTOH, if "Auto Calibration" is turned on, then the manual calibration will be used initially but the unit will continuously check how the measured pressure and the GPS-determined altitude vary and will gradually recalibrate based on the GPS data. The time constant for this recalibration seems to be about 30 minutes. That's long enough to smooth out the up and down jumps in GPS readings while still being reasonably quick compared to weather changes that affect the barometric pressure.

 

2) If you'll have the unit on continuously during the trip and in a position where it can get reasonable GPS reception then I'd tend to just rely on the automatic recalibration. I've found significant errors on some roadside signs that give the elevation. One on a hill near my home indicates an altitude of 2000' at a spot where my GPS and altimeter watch both consistently indicate around 1870' instead. But the sign lower on the hill at 1000' is in good agreement with my instruments. I tend to be more trusting of the signs on summits or passes where a specific altitude is given as opposed to the ones that give a round thousand foot number which may sometimes be placed where convenient rather than at the actual spot where the given altitude is reached.

Link to comment

Barometers in GPS units have been around for years. I have never found the use for one. They will report altitude more accurately than a non-barometer unit, if, and only if, they are properly calibrated. They must be calibrated often. You have to calibrate them against a known altitude or a known barometric pressure to have good accuracy. A regular GPS will give you altitude readings that are pretty darn accurate. Besides...Who really cares? I mean, you are where you are. Who cares if you really are at 7580 feet instead of 7500 as reported by your regular old non-barometer GPS? Some will claim they use it to predict weather...Watching the barometer climb or dive over several hours. I tend to rely on the TV or Radio for my weather predictions. They are more accurate than me guessing about it based on my GPS. The other thing they will do is track your elevation gain/loss over a time period. My legs will tell me that data!

Actually, tha baromiter feature can be useful if you don't have a weather radio or are out of NOAA broadcast range. Here is a weather prediction chart.

 

Over 30 ingh= good weather (unless you are already in fog)

around 29 ingh= cloudy

under 28 ingh= get your rain jacket

under 20 ingh= may be snowing

under 10 ingh= uh oh

under 3 ingh= you are probably on mount everest in a low pressure time or in a leaky plane

Edited by ossumguywill
Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...