On Feb 24, 9:18*am, wrote:
There seems to be a misconception around that gyros are required to implement a functional AH.
This is not true.

Gps derived attitude algorithms have been in the open literature for many years. Indeed, this is what is implemented in xcsoar.

A higher fidelity and faster AH is enabled by data fusion of gps, 3 axis accelerometers gyros and magnetometers. Emerging smartphones have these sensors.

To my knowledge, many of the apps available for smartphones do NOT implement the complete 9 degree of freedom data fusion - typically they assume unaccelerated dynamics (I.e not circling flight). This is just a warning should anyone decide to try those apps out.

Given the proliferation of open source sensor fusion software and
knowledge from the hobbyist UAV community, it's a very simple
programming project to implement a full 9 DF artificial horizon app.
Such apps already exist, just not for $5, yet...

Marc