Exactly. This is about the same what I described on the LocusMap forum as
possibly ideal way of progressive calibration of barometric altimeter.
Dne 18. února 2018 3:36:55 Kevin Kenny <[email protected]> napsal:
For what it's worth, a smartphone WITH a barometer (and an altitude
correction model on board, which I think is wired into Location Services on
Android) is quite a robust altitude indicator. The GPS altitude can be
compared with the barometer, integrated over a very long time - relative to
altitude changes, but short relative to the weather. That can yield the
sea-level pressure reading that will calibrate the barometer for short-term
variability.
My phone doesn't generally do quite as well as my wrist altimeter (which
often nails a known elevation within 5 m if the weather is stable), but
many, many times better than an unassisted GPS.
On Sat, Feb 17, 2018 at 6:53 PM, Poutnik <[email protected]> wrote:
Sure, but I was not speaking in context of aircraft, but e.g. of multi-day
mountain trekking. Neither I have heard about OSMAnd to be used for a
precise aircraft altitude control.
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.
Dne 17/02/2018 v 23:35 Robert Grant napsal(a):
I'm pretty sure that none of the devices listed by the op use barometric
altimeters; even the Garmin Glo is GPS altimetry. GPS is known for its
lack of precision in determining altitude. In aviation, old school
barometric altimeters are still the gold standard, but they require
periodic barometric pressure adjustment. While GPS is great for navigating
around the earth, it would be very foolish to use GPS altitude for landing
an aircraft. Bottom line: don't expect any phone with only GPS altitude
to agree precisely with a database supplied measurement.
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On Sat, Feb 17, 2018 at 1:41 PM, Harry van der Wolf <[email protected]>
wrote:
2018-02-17 19:41 GMT+01:00 Poutnik <[email protected]>:
While Europe subtracts altitude by the correction,
US adds altitude, so the higher value is the (over?)corrected one.
I didn't know that :)
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My Brouter profiles https://github.com/poutnikl/Brouter-profiles/wiki
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