PPP (Precise Point Positioning) is a GNSS-based technique used in inertial navigation systems (INS) to achieve high-precision positioning without the need for a base station or differential corrections. PPP relies on precise satellite orbit and clock data, which are typically broadcast from GNSS correction services, to improve positioning accuracy by correcting errors caused by atmospheric delays, satellite orbit inaccuracies, and clock errors.
How PPP Works in INS?
Raw GNSS Data Collection – The GNSS receiver collects raw data from satellites, including the satellite signal, pseudorange, and carrier phase measurements.
Precise Satellite Information – PPP uses precise orbit and clock corrections provided by correction services like IONEX (International GNSS Service) to reduce errors in satellite positioning.
Error Correction – PPP corrects ionospheric delays, tropospheric delays, multipath errors, and satellite clock discrepancies to calculate a highly accurate position.
Integration with INS – PPP can be combined with INS data (such as accelerometers and gyroscopes) to improve navigation, especially in GNSS-denied environments or for high-precision applications.
Applications of PPP in INS
✔ Surveying & Mapping – Used for geodetic surveying and high-precision mapping where real-time corrections are not feasible.
✔ Autonomous Vehicles & UAVs – Provides precise positioning for autonomous navigation in remote areas or environments where base stations are unavailable.
✔ Aerospace & Aviation – Used in aircraft and spacecraft navigation to ensure accurate positioning without reliance on ground-based systems.
Advantages of PPP in INS
✔ No Need for Base Stations – Unlike differential GNSS, PPP does not require a local reference station, making it ideal for remote or mobile applications.
✔ High-Precision Positioning – When using precise satellite data, PPP can provide centimeter-level accuracy, especially for geodetic applications.
✔ Global Coverage – PPP can be applied globally, providing continuous, high-accuracy positioning without the need for local infrastructure.
Challenges of PPP in INS
✔ Long Convergence Time – PPP typically requires a longer initialization period to achieve high-accuracy results compared to traditional GNSS methods.
✔ Dependence on Correction Data – The accuracy of PPP is heavily dependent on the availability of precise orbit and clock data.
✔ Susceptible to Signal Obstructions – Like all GNSS-based systems, PPP can suffer from signal loss in urban canyons or forests, affecting positioning.
