This paper presents an implementation of a postprocess
kinematic positioning technique similar to PPP (Precise
Point Positioning) but based on a network of stations. This
technique is independent of precise clock information because
it estimates satellite clock offsets ’on-the-fly’, and thence it only
needs reasonable accurate orbits information (for instance, IGS
precise, rapid or even predicted products) to work. Moreover,
with this approach the solution rate is only limited by data rate,
and not by the availability of precise satellite clock data rate as
it is the case with classical kinematic PPP techniques.
This procedure is referred to in this paper as ’Precise Orbits
Positioning’ (POP). Similar methods already exist in the literature,
such as ’network-based clocks’ and ’phase interpolation’;
however, with POP method both predicted and rapid IGS orbits
may also be used (not only precise products) without noticeable
degradation of positioning results, which is an important advantage.
The POP procedure involves multiple stations separated hundreds
of kilometers and there are a great number of unknowns
of several kinds. In order to ease the implementation of such
system some GPSTk-provided facilities were used, including a
run-time programmable general solver. A contribution of this
work is that a reference implementation is freely available at the
development version of the GPSTk source code, facilitating its
use and modification by other GNSS researchers.
The POP results were very similar (as expected) to the standard
kinematic PPP strategy, but yielding a higher positioning
rate. This higher positioning rate opens the way for post-process
kinematic positioning of vehicles that usually operate very far
from reference stations, such as aircraft. Also, our experiments
with this network-based processing strategy show additional
robustness in their results, even for receivers outside the network
area with long baselines.