Guys, I'll do a spreadsheet from my future bicycle rides with various sets of data using bike computers with barometric altimeters and GPS only phones. This data will get parsed in various ways based on source (GPS, baro), recording app (Osmand, Wahoo fitness) and post ride analysis programs (Strava, RideWithGPS, Garmin Connect). I may even have my buddies that I ride with help since we're all data junkies. My theory is that GPS will prove less accurate.
<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon> Virus-free. www.avast.com <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> On Sun, Feb 18, 2018 at 8:45 AM, Poutnik <[email protected]> wrote: > After some quick check via an Excel table, I evaluated atmospheric > influences on barometric altimeter : > > 1/ The biggest concern is for the air pressure trend. The difference 2 hPa > makes altitude error about 17-18 metres. The pressure change about 2 hPa/h > is easily and steadily happening during 12-18 hours before advent of the > warm front. A static altimeter would report you are climbing 18 metres in 1 > hour. Near a cold front, pressure trough or ridge, the air pressure can > change even faster. Once can easily check this effect during a day trip > with the same start and destination. Difference can be tens of meters. > 2/ Less concern is change of free air temperature wrt the standard > atmosphere, as altitude error is proportional to the altitude difference. > 10 deg C temp. change makes error about 33 metres for 1000 m difference. > This is more concern for the aircrafts than terrestrials. > 3/ The least concern is vertical temperature profile different from > standard atmosphere -00065K/m. The error grows with the square of the > altitude difference, but is usually small for the difference <1000 m. It is > usually biggest during foggy cold seasons. In winter isotermia in lower > 2000 m it makes about 11 m / 1000m and 44 m/2000m > > Dne 18/02/2018 v 00:39 Robert Grant napsal(a): > > While my experience agrees with you regarding accuracy and stability, it's > still better to know the local pressure setting, especially if landing an > aircraft without a radio altimeter. Setting an altimeter based on GPS > sounds quite rare to me. > > On Feb 17, 2018 3:12 PM, "Poutnik" <[email protected]> wrote: > >> As being trained in past as the military meteorologist, in pre-GPS era, >> I am aware of that. But the offset value is bigger than GPS accuracy of the >> static value averaged. BTW, the most handy way how to calibrate the >> barometric altimeter at unknown altitude is the GPS device. While >> barometric altimeters have superior short-term accuracy and stability, GPS >> devices have superior long-term accuracy and stability. Fortunately, for >> most personal usage, absolute altitudes are not that important, rather the >> relative changes. >> > > -- > Poutnik ( The Wanderer ) > > My Brouter profiles https://github.com/poutnikl/Brouter-profiles/wiki > > -- > You received this message because you are subscribed to the Google Groups > "Osmand" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- Robert Grant -- You received this message because you are subscribed to the Google Groups "Osmand" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
