Titolo della tesi: GNSS Point Positioning and Variometric Solutions Integration to Support and Improve Real-Time Navigation
Nowadays, Global Navigation Satellite Systems (GNSS)
technology is pervasive in the civilian daily life. Among
all the possible application elds, satellite navigation systems
play a major role in kinematic applications ranging
from pedestrian or vehicle navigation to people and goods
tracking. Furthermore, the recent developments, in both
satellite and user segments, are pushing forward the development
of innovative and more accurate dynamic applications
also on mass-market GNSS receivers as Android
smartphones.
In this variety of possible applications, di erent GNSSbased
algorithms can be considered depending on the targeted
requirements. The main aim of this thesis is to introduce
and validate GNSS POWER, a standalone positioning
algorithm developed as a trade-o between traditional
code-based and phase-based approaches. GNSS POWER
relies on both pseuodorange and carrier-phase observations.
The algorithm is based on a loosely coupling strategy between
a robust SPP and the variometric velocities estimated
leveraging on variometric phase observations and
kinematic Variometric Approach for Displacements Analysis
Stand-alone Engine (kin-VADASE). The use of variometric
phase measurements allows to estimate instantaneous
3D velocity with accuracy of few mm/s. However,
considering the contribute of pseudorange observations
analysed using an SPP algorithm, GNSS POWER
can target absolute accuracy of few decimetres and epochby-
epoch displacements with few centimetres uncertainty.
The methodology is validated in both static and kinematic
conditions with di erent GNSS receivers using Global Positioning
System (GPS) and Galileo L1/E1 observations.
The results in static scenario demonstrates mean accuracy
around 0.5 m for the horizontal components and around
1.0 m in the height using one week of GNSS measurements
from a Continuous Operating Reference Stations (CORS)
receiver. In order to target the same accuracy level on
poorer observations, a cycle slip detector, based on variometric
phase measurements, and two methodologies for
robust adjustment - i.e. LOOCV and recursive Huber function
- are introduced and validated on data from a u-blox
ZED F9P and a Xiaomi Mi 8. Furthermore, the tests
in kinematic scenarios in open sky conditions demonstrate
comparable results with geodetic receivers. Horizontal submeter
accuracy can be achieved using Android smartphones
as well. A marked improvement with respect to the traditional
SPP is also observed in vehicle navigation scenario
for both high-end receiver and Android smartphones.
Additionally, a real-time GNSS POWER tool is introduced
and described in the thesis with the main purpose to exploit
orbits, clocks and code biases SSR corrections to increase
the overall accuracy. As demonstrated from static tests, the
availability of real-time SSR corrections streamed in Radio
Technical Commission for Maritime Services (RTCM)
format further enhances the accuracy of GNSS POWER
solutions. A comparison on one week of GNSS measurements
from a CORS station highlights a mean improvement
of 0.05 m, 0.10 m and 0.04 m in the East, North and
Up Root Mean Square Error (RMSE) with respect to the
use of only broadcast information. The test in kinematic
scenario, carried out on a shorter time interval - i.e. 25
minutes -, con rms the importance of applying SSR corrections
not only on geodetic receivers but also on Android
smartphones. For instance, the enhancement with respect
to the solution based on broadcast navigation message in
the horizontal R50 and R95 can reach the 18%. For all the
kinematic datasets in analysis, the epoch-by-epoch accuracy
of GNSS POWER is in the range of few centimetres
demonstrating high-precision in retrieving tracks geometry.
Based on the results disccused in this thesis, GNSS
POWER is now becoming a key GNSS algorithm in different
research and commercial projects with focus on topographic,
mHealth and precision agriculture applications.
In conclusion, this thesis introduces and validates a realtime
standalone GNSS algorithm able to support instantaneous,
stable and reliable Position, Velocity and Time
(PVT) solutions with absolute accuracy of few decimetres
and epoch-by-epoch displacements of few centimetres.