Article
Investigating Practical Impacts of Using Single-Antenna and
Dual-Antenna GNSS/INS Sensors in UAS-Lidar Applications
Ryan G. Brazeal
1,2
, Benjamin E. Wilkinson
1,2,
* and Adam R. Benjamin
3
Citation: Brazeal, R.G.; Wilkinson,
B.E.; Benjamin, A.R. Investigating
Practical Impacts of Using
Single-Antenna and Dual-Antenna
GNSS/INS Sensors in UAS-Lidar
Applications. Sensors 2021, 21, 5382.
https://doi.org/10.3390/s21165382
Academic Editor: Kamil Krasuski
Received: 4 July 2021
Accepted: 6 August 2021
Published: 9 August 2021
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
published maps and institutional affil-
iations.
Copyright: © 2021 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/).
1
Geomatics Program, School of Forest, Fisheries, and Geomatics Sciences, University of Florida,
Gainesville, FL 32611, USA; ryan.brazeal@ufl.edu
2
Geospatial Modeling and Applications Lab, School of Forest, Fisheries, and Geomatics Sciences,
University of Florida, Gainesville, FL 32611, USA
3
Geomatics Program, Fort Lauderdale Research & Education Center, School of Forest, Fisheries, and
Geomatics Sciences, University of Florida, Fort Lauderdale, FL 33314, USA; abenjamin1@ufl.edu
* Correspondence: benew@ufl.edu
Abstract:
Data collected from a moving lidar sensor can produce an accurate digital representation of
the physical environment that is scanned, provided the time-dependent positions and orientations of
the lidar sensor can be determined. The most widely used approach to determining these positions
and orientations is to collect data with a GNSS/INS sensor. The use of dual-antenna GNSS/INS
sensors within commercial UAS-lidar systems is uncommon due to the higher cost and more complex
installation of the GNSS antennas. This study investigates the impacts of using a single-antenna and
dual-antenna GNSS/INS MEMS-based sensor on the positional precision of a UAS-lidar generated
point cloud, with an emphasis on the different heading determination techniques employed by each
type of GNSS/INS sensor. Specifically, the impacts that sensor velocity and acceleration (single-
antenna), and a GNSS compass (dual-antenna) have on heading precision are investigated. Results
indicate that at the slower flying speeds often used by UAS (
≤
5 m/s), a dual-antenna GNSS/INS
sensor can improve heading precision by up to a factor of five relative to a single-antenna GNSS/INS
sensor, and that a point of diminishing returns for the improvement of heading precision exists at a
flying speed of approximately 15 m/s for single-antenna GNSS/INS sensors. Additionally, a simple
estimator for the expected heading precision of a single-antenna GNSS/INS sensor based on flying
speed is presented. Utilizing UAS-lidar mapping systems with dual-antenna GNSS/INS sensors
provides reliable, robust, and higher precision heading estimates, resulting in point clouds with
higher accuracy and precision.
Keywords: unoccupied aerial system; UAV; drone; GPS; inertial; heading; mobile mapping
1. Introduction
Three-dimensional mapping of natural or built environments using high-resolution
light detection and ranging (lidar) sensors onboard unoccupied aerial systems (UAS) is
now a common practice. Recent advancements in robotics and real-time computing have
led to the possibility of autonomous UAS-lidar mapping operations in global navigation
satellite system (GNSS)-denied environments (e.g., underground mines) [
1
]. However,
the more common application of autonomous UAS-lidar mapping still occurs in outdoor
environments [
2
]. For observations collected from a moving lidar sensor to produce
an accurate digital representation (i.e., point cloud) of the physical environment that is
scanned, the time-dependent positions and orientations of the lidar sensor with respect
to a fixed reference frame are needed. The most widely used approach to determining
these positions and orientations is to collect data with a GNSS-aided inertial navigation
system (GNSS/INS) [
3
]. As a result of advancements in the miniaturization of electronics,
GNSS/INS sensors containing high-accuracy GNSS receivers and micro-electro-mechanical
system (MEMS)-based inertial measurement units (IMUs) are now commercially available
Sensors 2021, 21, 5382. https://doi.org/10.3390/s21165382 https://www.mdpi.com/journal/sensors
