Citation: Li, Q.; Dong, Y.; Wang, D.;
Wu, J.; Zhang, L. Real-Time Precise
DGNSS/INS Integrated Relative
Positioning with High Output Rate
and Low Broadcast Rate for
Kinematic-to-Kinematic Applications.
Remote Sens. 2022, 14, 2053. https://
doi.org/10.3390/rs14092053
Academic Editors: Damian
Wierzbicki and Kamil Krasuski
Received: 30 March 2022
Accepted: 23 April 2022
Published: 25 April 2022
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
published maps and institutional affil-
iations.
Copyright: © 2022 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
Article
Real-Time Precise DGNSS/INS Integrated Relative Positioning
with High Output Rate and Low Broadcast Rate for
Kinematic-to-Kinematic Applications
Qingsong Li
1,
*, Yi Dong
2
, Dingjie Wang
1
, Jie Wu
1
and Liang Zhang
3
1
College of Aerospace Science and Engineering, National University of Defense Technology,
Changsha 410073, China; wangdingjie11@nudt.edu.cn (D.W.); wujie@nudt.edu.cn (J.W.)
2
State Key Laboratory of Astronautic Dynamics, Xi’an Satellite Control Center, Xi’an 710043, China;
dongyi13@nudt.edu.cn
3
Institute of Information and Navigation, Air Force Engineering University, Xi’an 710077, China;
zhangliang_nudt@nudt.edu.cn
* Correspondence: liqingsong10@nudt.edu.cn
Abstract:
High-output-rate relative positions are required for high-speed safety-critical kinematic-
to-kinematic applications such as pre-crash sensing and shipboard landing. We propose a real-time,
high-output-rate relative positioning method based on the integration of a real time kinematic (RTK)
differential global navigation satellite systems (DGNSS) relative positioning algorithm, carrier-phase-
based tightly coupled GNSS/Inertial navigation system (TC-GNSS/INS) integration algorithm and
polynomial prediction algorithm for position increment. We focus on the rarely studied issue that
data broadcast rates and sampling rates have effects on the integrated relative positioning accuracy
under different motion states of a moving base. A vehicle-to-vehicle field test with a frequently
turning base demonstrates the advantages of the proposed method, such as low bit rate of broadcast
data, high output rate of position solutions and excellent real-time tolerance of latency. The results
show that compared with the 10-Hz output of sole RTK DGNSS relative positioning, the proposed
method can provide centimeter-level-accuracy relative positions at an output rate of 125 Hz with
a sampling rate of 1 Hz, and the bit rate can be reduced by 83.12%. A UAV-to-boat field test with
straight-line-motion moving base is then carried out to validate the applicability of the proposed
system for aircraft applications. The results show that the broadcast rate of position increments of the
moving base can be further reduced.
Keywords:
DGNSS/INS integrated; high output rate; precise relative positioning; low bit rate;
kinematic-to-kinematic
1. Introduction
Nowadays, many safety-critical kinematic-to-kinematic applications require output
rates of precise relative positions of 10 Hz to 50 Hz or more, such as vehicle-to-vehicle coop-
erative safety applications [
1
], automated air refueling and shipboard relative
landing [2]
.
Automatic cruise control applications require an update rate of between 10 Hz and
20 Hz [3]
.
Cooperative vehicular applications such as lane-change, emergency brake lights and for-
ward collision warnings require 10 Hz and the pre-crash sensing application even requires
an output rate of up to 50 Hz [
1
]. High-speed applications such as autopilot and airborne
positioning also require a sampling rate of GNSS data of 50 Hz [4].
Carrier-phase-based RTK DGNSS relative positioning technology is widely adopted
in kinematic-to-kinematic applications to provide precise relative positioning such as
vehicle-to-vehicle cooperative positioning [
2
,
5
], formation flight [
6
,
7
], collision detection
between aircrafts [
8
] and shipboard landing [
9
,
10
]. Raw GNSS observations should be
broadcast from a moving base to a rover by radio; the synchronized observations are
Remote Sens. 2022, 14, 2053. https://doi.org/10.3390/rs14092053 https://www.mdpi.com/journal/remotesensing
