integrateMeasurement() data frame unclear

[hmellor]

Description

In CombinedImuFactorsExample.cpp it is stated that the IMU data is provided aligned to NED (the navigation frame).

However, the documentation for gtsam::PreintegratedCombinedMeasurements::integrateMeasurement() states that the IMU data should be provided in body frame.

Only one of these can be correct and I am uncertain which is.

[tmcg0]

Measurements should be provided in the body frame. I think the example file comment is just misleading---perhaps the referenced comment line should end names in X, Y, Z instead of N, E, D.

[mikesheffler]

Agreed. Saying 'N, E, D', may have been the author's way of describing a coordinate system that could perhaps be more accurately described as 'forward, right, down'. At least, I know I've made that specific whoopsie :)

[tmcg0]

@hmellor you could always make a PR that cleans up that comment. :) clarity is always a plus.