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Polar S710 Altitude - Very inconsistent readings(8 posts)

Polar S710 Altitude - Very inconsistent readingsFez
Dec 19, 2002 2:57 PM
I used the altitude for my regular rides. Each time the readings are different. Everything is different - ascent, min, max. Have used it more than 10 times on the same route in same weather.

Is altitude function worthless on this?
re: Polar S710 Altitude - Very inconsistent readingsChen2
Dec 19, 2002 3:20 PM
I haven't tried one of these yet, but I'd like to. As you know, the altitude calculation is a function of barametric pressure which vaies, sometimes rapidly. Something that might help you is a topographic map. If you can calibrate your instrument to a reference point on a map then the altitude calculations should be good for a while, until the pressure changes. You can print off a free topomap of any area in the U.S. from www.topozone.com. Search using the nearest city. The software has some scaling controls, minimal but hey, it's free.
~Al
Polar S710 Altitude - Very inconsistent readings because........gogene
Dec 19, 2002 3:46 PM
....... the 710 is a barometric altimeter, altitude readings will vary with temperature, weather etc. The weather is never the "same". There is nothing you can do about that. You can however set your altimeter at the start of your ride at 0. You will still have your total altitude gain at the end of the ride, and your PC charts will show all of the elevation gains and losses. If the ride begins and ends at the same place, you can adjust that setting in the altitude settings of the ride chart on your PC. It's easy to do.
Polar S710 Altitude - Very inconsistent readings because........Fez
Dec 20, 2002 6:05 AM
The readings are not even close, despite doing the same ride. Altitude gain is inconsistent, and the amount of ascent or descent between 2 points is also very inconsistent. Not to mention the current altitude readings are way off despite resetting the values at the start of each ride.

A GPS handheld caclulated altitude better, but not perfect. And they constantly recaclulated the reading so recalibration was unnecessary.

Are dedicated altimeters like Suunto any better at giving more accurate and consistent readings?
Polar S710 Altitude - Very inconsistent readings because........Chen2
Dec 20, 2002 6:49 AM
Sounds like you have a bad unit.
Altitude not consistent because it is a barometric device.gogene
Dec 20, 2002 8:11 AM
ANY altimeter, that is barometric, depends on air pressure to read altitude. If the air pressure (density) changes, the effective altitude will also.It you turned on your altimeter, calibrated it to your known altitude and left it on your front lawn for several hours, you would see an elevation gain and/or loss. This is due to the air pressure changing as time goes on. If the temperature gets warmer, the air density becomes less, therefore the air pressure becomes less, therefore the (effective) altitude has changed. If the temperature drops, the opposite happens.

So no barometric altitude device is going to be 100% accurate, 100% of the time. This is one reason is is better to set the altitude at your start to zero, if you want to know how much elevation you have gained, not necessarily how high you are. If you want to know height, you MUST calibrate a barometric altimeter to a know altitude before EACH use. Just as aircraft that use barometric altimeters do. There is no other way short of a GPS.
Polar S710 Altitude - Very inconsistent readings because........Lactate Junkie
Dec 20, 2002 11:14 AM
You really cannot set it to zero and get accurate results unless you live close to sea level. If you are up in the mountains and use zero as your altitude, the unit will significantly under measure your altitude gain. This is because there is a lot less pressure change to a 100' change in altitude at 5000 ft than there is at sea level. You really have to calibrate to a known altitude on a regular basis, especially if you live somewhere where there are a lot of weather changes.
Any altimeter is inconsistentfrankamo
Dec 20, 2002 6:29 AM
Even those in aircraft. As others mentioned, there are many parameters that affect them.

I've actually found the S710 to be more consistent than my plane's. After a two hour trip the S710 is much closer to the actual when I return to the house, than the plane's is to the airport's altitude after a two hour flight.