SV PDOP

Fig. 11. Number of satellites tracked and corresponding PDOP values.

the LAMBDA and the MC-LAMBDA methods, two-baseline processing.

is due to the higher number of satellites tracked in the second test.

of the epochs in test *T* − *I* and more than 88% in test *T* − *I I*.

The success rate marked by the LAMBDA and MC-LAMBDA methods applied to both flight tests is reported in Table 1 (Giorgi et al., 2011). The single-epoch performance of the

GNSS Carrier Phase-Based Attitude Determination 215

*T* − *I T* − *I I* LAMBDA MC-LAMBDA LAMBDA MC-LAMBDA 5.8 81.5 24.7 88.1

Table 1. *T* − *I* and *T* − *I I* tests: unaided single-epoch, single-frequency success rate (%) for

unconstrained method are rather unsatisfactory. The correct set of integer ambiguities is resolved only for 5.8% of time in test *T* − *I* and in 24.7% of time in test *T* − *I I*. The difference

Instead, application of the MC-LAMBDA method yields a strong performance improvement. The constrained method is capable of providing the correct integer solution for more than 80%

Both airborne tests confirm the very large improvement that is obtained by strengthening the underlying model with the inclusion of geometrical constraints. It is stressed that all the ambiguity resolution performance reported are obtained by processing the GNSS signals without any a priori information or assumption about the attitude or the aircraft motion. Also, mask angles, elevation-dependent models, dynamic models or any kind of filtering are not

> Heading *σψ* [deg] 0.07 Elevation *σθ* [deg] 0.20 Bank *σφ* [deg] 0.12

Table 2. *T* − *I I* test: standard deviations of the differences between GPS and INS attitude

High single-epoch success rates yield precise epoch-by-epoch attitude solutions for the larger part of the flights duration. The attitude angles based on the correctly fixed integer

<sup>0</sup> <sup>2000</sup> <sup>4000</sup> <sup>6000</sup> <sup>8000</sup> <sup>10000</sup> <sup>12000</sup> <sup>14000</sup> <sup>16000</sup> <sup>1</sup>

(b) *T* − *I I*

Epoch
