There is a 330m difference between the position of the GPS and Doppler at powerdown. Something?, or nothing?
This is something that has nagged at me. As I understand it the TANS works as follows:
1. GPS produces position A;
2. Doppler produces position B;
3. TANS 'blends' A and B, using an algorithm with a weighting to A to arrive at C;
4. TANS displays C to the crew; but
5. The aircraft is almost certainly at D, because the algorithm at 3 is only an approximation of the relationship between A & B.
The fact that the final position data does not reflect the point of impact means that all the other position data is out by some factor of 330m (and this 'could' be greater than 1).
Further without knowlegde of the algorithm it may be that the error factor does not stay constant, particularly if other factors affect the weighting.
At the very least this merits further examination.
EG