GPS satellites can be used to determine the attitude of other satellites also. I am not an expert in this field, but it might work the same way for tracking of people/cars on Earth.
Anyway, this is how it works for satellites.

GPS sensors can be used to determine attitude provided that
at least 3 antennas are vailable. The 4th is needed for timing.
Slave and master are 2 antennas mounted on the s/c. If the distance $b$
is known we can detect the s/c orientation in space. Taking the
projection of $\underline{b}$ on the direction $\underline{S}$ of the incoming GPS signal
we obtain the path difference of the signal received by the 2 antennas as $\underline{S}^T \underline{b}$.
The position of the GPS satellite is known, therefore $\underline{S}$ is known in the geocentric reference frame if we know the position of the master antenna.
Measuring the path difference
$\Delta r = \underline{S}^T \underline{b}$
and transforming the vector $\underline{S}$ from geocentric to body frame
$\underline{S} = AS$
$\Delta r = S^T A^T \underline{b} $
the unknown is the rotation matrix A.
Having 3 independent measurements:
$\Delta r_{11} = S_1^T A^T \underline{b}_1 $ baseline 1 GPS satellite 1
$\Delta r_{21} = S_2^T A^T \underline{b}_1 $ baseline 1 GPS satellite 2
$\Delta r_{12} = S_1^T A^T \underline{b}_2 $ baseline 2 GPS satellite 1
$\Delta r_{22} = S_2^T A^T \underline{b}_2 $ baseline 2 GPS satellite 2
...
2 baselines are required, otherwise if you have a single baseline
you cannot determine the rotation around that baseline.
To determine attitude minimize the cost function:
$J = \sum_{i = 1}^{N_S} \sum_{j = 1}^{N_b} (\Delta r_{ij} - S_i^T A^T b_j)$