Navigation Systems Lecture 9: Error Calculation and PVT Estimation

This flashcard set covers key terminology from Lecture 9 of the TTT4150 Navigation Systems course, focusing on quality control, error detection (RAIM/reliability), and PVT estimation methods.

NLOS

Non Line Of Sight propagation, where the direct path of a signal is completely blocked and the receiver only tracks secondary reflected paths, often leading to large measurement outliers.

RAIM

Receiver Autonomous Integrity Monitoring; a technique used to detect and isolate faulted satellites based on redundant measurements.

Circular Operating Mode

Also known as Time of Arrival ($TOA$), where the system solves for the user clock offset or error.

Hyperbolic Operating Mode

Also known as Time Difference of Arrival ($TDOA$), where the system does not solve for the user clock offset or error.

Inner Reliability

A measure of how large an error in the input observable can be, in magnitude, for a defined level of confidence.

Outer Reliability

A measure of how large an error in the output state estimate can be caused by an error in a specific observation.

PVT

An abbreviation for Position, Velocity, and Time, representing the common states estimated in GNSS solutions.

Doppler Effect

A measure of relative velocity or range rate between the satellite and the receiver, appearing as a frequency shift ($f_R$ relative to $f_s$).

ADR

Accumulated Delta Range; a measurement derived from integrated Doppler shift, often achieving noise levels under $1\,cm$.

Meaconing

The use of rogue repeaters to re-transmit GNSS signals, which can cause a receiver to calculate its position as being at the repeater's roof antenna.

Innovation Monitoring

The process in Kalman filtering used for error handling by checking if current measurements are consistent with the prior state of the system.

Least Squares Estimator

A deterministic estimator that depends only on current measurements to form an estimate for the current epoch.

RTKlib

A software package used for handling and processing GNSS data, specifically discussed for use in post-processing.

Ephemeris

Data decoded by a receiver that includes orbital parameters and health flags used to determine if a satellite should be trusted.

GBAS

Ground Based Augmentation System; a field where improperly executed orbit maintenance is considered a valid threat.

Clock Offset Rate

A state calculated alongside velocity in a $PVT$ solution, analogous to how clock offset is calculated with position.