David Abmayr <[email protected]> writes:

> The reason I ask it that the barometric altitude reads 9700 ft, but
> the GPS reported 10,240 ft.

That's not unusual.  Adrian used to go pull atmospheric sounding data
From NCAR after launches to re-compute baro altitudes with something
closer to reality than the standard model of the atmosphere we all use
for in-device firmware.  Even then, though, using baro pressure as a
proxy for altitude is still just an approximation.

> Most of my
> flights have been with the TeleMetrum 1.2, and the GPS clearly doesn't get
> a good fix until well after apogee. My TeleMetrum 2.0 and TeleMega seem to
> work much better, with good fixes at apogee.

Right.  The Venus chips we used on early TeleMetrum boards worked fine
for finding an airframe after flight, but their firmware did not behave
well in high dynamic situations.  The uBlox parts we use now are much
better suited for rocketry.  This past weekend at NCR North, for
example, son Robert and I had great GPS traces on all of our flights
using a mix of TeleMetrum v2 and TeleMega boards.

Bdale

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