ned2geodetic returns wrong altitude for +ve values of down

[sytelus]

In NED +down values should decrease the altitude however when converting to geodetic it returns +ve altitude instead. If you look at the equations in ecef2geodetic then it can be easily seen that returned altitude value will always be positive. I think this happens because sqrt(x) is supposed to be +/- value but in code we always end up using only + value.

[philippmaa]

I have a similar problem. When I use this framework geodetic2Enu is perfect, but the other way enu2Geodetic results in continuously decreasing altitude.
I figured out that during the calculation, precisely in ned2Ecef the z value stays always the same, even if given lat, lon, alt change.
Can anybody help me out?

Kind regards
philippmaa

EDIT: I solved the issue. When calculating ned_to_ecef_matrix_ (what has to be the inverse of ecef_to_ned_matrix_) as:

ned_to_ecef_matrix_ = nRe(initial_latitude_, initial_longitude_).transpose();

there are inaccuracies in ned_to_ecef_matrix_. In my case these inaccuracies lead to errors in altitude up to 15m.
I changed this line to:

ned_to_ecef_matrix_ = ecef_to_ned_matrix_.inverse();

With this change the results are perfect. The only problem is, I think it's not good to calculat the inverse of a matrix.
If you have any hints, please let me know.