What type of coordinates is used in iNav code, and why comments "x axis of accelerometer is pointing backwards"?

[lida2003]

Hi

I'm new to this code. And I have two quesitons here:

a) What's the body frame coordinates we use in code? ENU, xEast-yNorth-zUp , am I right?
b) In function imuMahonyAHRSupdate(when we use COG), why comments "x axis of accelerometer is pointing backwards." what does this mean?

BTW, x axis of accelerometer is pointing to the head of aircraft, right?

[lida2003]

Is ENU the body frame coordination system for iNav's code?

[breadoven]

Defined here https://github.com/iNavFlight/inav/wiki/Developer-info

[lida2003]

Thanks for the links.

BTW, it seems NEU Coordinate System(iNav) is quite different from the description from https://ww2.mathworks.cn/help/map/choose-a-3-d-coordinate-system.html.

And I also noticed that :

The x axis is aligned with the vector to the north pole (tangent to meridians).
The y axis points to the east side (tangent to parallels)
The z axis points up from the center of the earth

It's NOT right-handed (RH) Cartesian coordinate systems.

So Is it left-handed (LH) Cartesian coordinate systems used in iNav Code?

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[lida2003]

Does betaFlight/cleanFlight/iNav use the same coordinate system (left-handed (LH) Cartesian NEU coordinate systems)?

PS: BF & iNav are cloned from cleanflight (Multiwii).

[lida2003]

Thanks guys, I might be know the answer. xEast-yNorth-zUp + yaw(reverse), details see below link: BetaFlight深入传感设计之九：传感坐标系/机体坐标系/导航坐标系/经纬度坐标系