# Deep urban unaided precise Global Navigation Satellite System vehicle positioning

## TL;DR

This study demonstrates that unaided differential GNSS can achieve 17-cm accuracy in deep urban environments without additional sensors, using a dense reference network and advanced processing techniques.

## Contribution

The paper presents the first comprehensive evaluation of unaided urban CDGNSS positioning achieving high accuracy and availability without sensor aid.

## Key findings

- Achieved 17-cm 3D positioning accuracy with >87% availability.
- Identified key factors: data wipeoff and dense reference network.
- Outperformed existing unaided GNSS systems in urban settings.

## Abstract

This paper presents the most thorough study to date of vehicular carrier-phase differential GNSS (CDGNSS) positioning performance in a deep urban setting unaided by complementary sensors. Using data captured during approximately 2 hours of driving in and around the dense urban center of Austin, TX, a CDGNSS system is demonstrated to achieve 17-cm-accurate 3D urban positioning (95% probability) with solution availability greater than 87%. The results are achieved without any aiding by inertial, electro-optical, or odometry sensors. Development and evaluation of the unaided GNSS-based precise positioning system is a key milestone toward the overall goal of combining precise GNSS, vision, radar, and inertial sensing for all-weather high-integrity high-absolute-accuracy positioning for automated and connected vehicles. The system described and evaluated herein is composed of a densely-spaced reference network, a software-defined GNSS receiver, and a real-time kinematic (RTK) positioning engine. A performance sensitivity analysis reveals that navigation data wipeoff for fully-modulated GNSS signals and a dense reference network are key to high-performance urban RTK positioning. A comparison with existing unaided systems for urban GNSS processing indicates that the proposed system has significantly greater availability or accuracy.