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Projecte llegit

Títol: Software modules for a precise positioning GNSS receiver

Estudiants que han llegit aquest projecte:

Director/a: OLMOS BONAFÉ, JUAN JOSÉ

Departament: TSC

Títol: Software modules for a precise positioning GNSS receiver

Data inici oferta: 18-07-2024     Data finalització oferta: 18-03-2025


Estudis d'assignació del projecte:
    DG ENG AERO/SIS TEL
Tipus: Individual
 
Lloc de realització: EETAC
 
Paraules clau:
GNSS, PPP, RTK, Navigation
 
Descripció del contingut i pla d'activitats:
This proposal aims at building several software modules for a GNSS receiver allowing for precise positioning.
The final objective of the receiver is to obtain the user PVT solution applying a Kalman Filter while reducing the range error down to cm accuracy.
The input data will be precise satellite orbits coming from IGS SP3 files and satellite clock offsets coming from RINEX CLK files.
As a first task, the preprocessing software module will be in charge of measurements cleaning and exclusion due to different criteria. For example:
- Check for minimum elevation angle of satellites.
- Do not exceed the maximum number of satellite parallel processing.
- Check for a minimum Carrier-To-Noise Ratio in the measurements.
- Detect phase cycle slips in the received signal.
Finally the preprocessing module will be in charge of building the iono-free combination to remove the ionosphere delay from the pseudo-range measurements.
As a second task a corrections module will be built to correct other errors included in the observables, like Sagnac effect, satellite clock bias, troposphere delay, etc.
The third task will apply the Kalman filter to obtain the PVT navigation solution.
Finally, the user performances will be obtained and reported.
 
Overview (resum en anglès):
This thesis presents PEPPUS, a comprehensive GNSS processing tool implementing Precise Point Positioning (PPP) to achieve centimetre-level positioning accuracy across a continental network of reference stations. PEPPUS comprises three sequential modules:

PPVE (Preprocessing & Validation Engine): Cleans raw RINEX observations by applying elevation masks, signal-to-noise and continuity checks, cycle-slip detection (Melbourne-Wübbena), and dual-frequency ionosphere-free and geometry-free combinations, yielding high-quality code and phase observables.

PCOR (Corrections Module): Applies precise satellite orbital (SP3), clock (CLK), relativistic, Sagnac, antenna phase-centre, tropospheric (Saastamoinen + mapping function), and User Equivalent Range Error (UERE) corrections, producing residuals used to assess correction performance.

KPVT (Kalman PVT Solver): Implements an extended Kalman filter to fuse corrected pseudorange and carrier-phase measurements, estimating receiver position, clock bias, tropospheric delay, and phase ambiguities recursively. Performance metrics include convergence time, Dilution of Precision, and horizontal/vertical error statistics.

Validation across five European stations (ALYA in Egypt, LAPA in Finland, LPIA in Canary Islands, RKKA in Iceland and TLSA in France) demonstrates robust global performance: convergence times of 15-50 minutes, horizontal/vertical errors below 0.3 m/0.2 m post-convergence, and consistent UERE behavior with elevation. The results confirm PEPPUS's capability for reliable centimetre-level positioning using PPP and highlight the importance of comprehensive preprocessing and correction modeling.

This work was carried out as part of the GNSS Academy project, which provided the raw software framework and expert guidance for the development of the PEPPUS tool.

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