Polar 725 Altimeter Question

[PeterF]

I have recently purchased a Polar 725 HRM. I enjoy it quite a bit especially with the speed and cadence sensors. One question I have is regarding the Altimeter. I constantly have to re-set it to my home altitude. Does anyone else have this problem? I'm assuming it is using atmospheric pressure to determine altitude (this is a real moving target in coastal Massachusetts). What is the ideal pressure to get an accurate reading?

 

[BigDave]

I have the same problem. I don't really use the altitude readings, but the amount of climbing is helpful. Maybe in higher altitudes it is more reliable. I'm only at 310 feet.

 

[Arathald]

I don't know anything about this particular product, but I may be able to offer assistance. If the unit does indeed judge altitude by pressure, then you will never be able to set a home altitude correctly (because pressure constantly changes). The altimeter is only going to be as accurate as the pressure is steady, but if the pressure is fairly steady, then at just about any presuure, it should register altitude differences correctly. Any variation in pressure based on weather is going to throw it off, so it is best to figure that it's going to be a bit inaccurate, especialy on days with constantly changing weather.

 

[impakt]

I don't know anything about this particular product, but I may be able to offer assistance. If the unit does indeed judge altitude by pressure, then you will never be able to set a home altitude correctly (because pressure constantly changes). The altimeter is only going to be as accurate as the pressure is steady, but if the pressure is fairly steady, then at just about any presuure, it should register altitude differences correctly. Any variation in pressure based on weather is going to throw it off, so it is best to figure that it's going to be a bit inaccurate, especialy on days with constantly changing weather.

exactly.. all altimeters you must set a base point altitude. and calibrate the unit each time you are going to use it from that base point. it uses air pressure, air pressure changes.

a problem? no.

the way they are designed to work? yes

do they work? yes.like any other altimeter, but like the last person said, weather will effect it. but on a 3-6 hour ride how much does the weather actually change?

 

[PeterF]

exactly.. all altimeters you must set a base point altitude. and calibrate the unit each time you are going to use it from that base point. it uses air pressure, air pressure changes.

a problem? no.

the way they are designed to work? yes

do they work? yes.like any other altimeter, but like the last person said, weather will effect it. but on a 3-6 hour ride how much does the weather actually change?

I do feel that the "feet ascended" feature does work very well which is really why I wanted this model. I do have a good home point measurement (I ride by the ocean every day, so I'm pretty sure that it's accurate), I was just curious if resetting it daily was normal. Thank you everyone for your help.

Pete

 

[dgregory57]

If you have ever listened to air traffic control during a flight, you will frequently hear wind direction, wind speed (both for obvious reasons) and barometric pressure, usually expressed as "altimeter", so this same phenomenon impacts the expensive altimeters in jet liners... So, yes, if accuracy of current altitude is important, you will have to regularly set your altimeter.

 

[mises]

I have the same problem. I don't really use the altitude readings, but the amount of climbing is helpful. Maybe in higher altitudes it is more reliable. I'm only at 310 feet.

They are more accurate at higher altitudes. But in my experience the polar units generally do about as well as GPS triangulation (non-military anyway) and sometimes better.