
1
Patchwork: Concentric Zone-based Region-wise
Ground Segmentation with Ground Likelihood
Estimation Using a 3D LiDAR Sensor
Hyungtae Lim
1
, Student Member, IEEE, Minho Oh
1
, Hyun Myung
1
, Senior Member, IEEE
Abstract—Ground segmentation is crucial for terrestrial mo-
bile platforms to perform navigation or neighboring object
recognition. Unfortunately, the ground is not flat, as it features
steep slopes; bumpy roads; or objects, such as curbs, flower beds,
and so forth. To tackle the problem, this paper presents a novel
ground segmentation method called Patchwork, which is robust
for addressing the under-segmentation problem and operates
at more than 40 Hz. In this paper, a point cloud is encoded
into a Concentric Zone Model–based representation to assign an
appropriate density of cloud points among bins in a way that
is not computationally complex. This is followed by Region-wise
Ground Plane Fitting, which is performed to estimate the partial
ground for each bin. Finally, Ground Likelihood Estimation is
introduced to dramatically reduce false positives. As experimen-
tally verified on SemanticKITTI and rough terrain datasets,
our proposed method yields promising performance compared
with the state-of-the-art methods, showing faster speed compared
with existing plane fitting–based methods. Code is available:
https://github.com/LimHyungTae/patchwork
Index Terms—Range Sensing; Mapping; Field Robots; Ground
Segmentation
I. INTRODUCTION
I
N recent years, there has been an increased demand to
perceive surroundings for mobile platforms, such as Un-
manned Ground Vehicles (UGVs), Unmanned Aerial Vehicles
(UAVs), or autonomous cars. To accomplish this, numerous
researchers have applied various 3D perception methods [1]–
[4]. In particular, a 3D light detection and ranging (LiDAR)
sensor has been extensively deployed due to allowing for
centimeter-level accuracy and omnidirectional sensing, as well
as its ability to measure great distances compared with stereo
cameras [1], [5], [6]. Accordingly, a 3D point cloud captured
by a LiDAR sensor is utilized for semantic segmentation [7],
[8], tracking [9], detection [10], and so forth.
In this paper, we specifically focus on ground segmentation
tasks [11], [12]. There are two main purposes of ground
segmentation. One is to estimate the movable area [3], [13] for
This work was supported by the Industry Core Technology Development
Project, 20005062, Development of Artificial Intelligence Robot Autonomous
Navigation Technology for Agile Movement in Crowded Space, funded by
the Ministry of Trade, Industry & Energy (MOTIE, Republic of Korea) and
by the research project “Development of A.I. based recognition, judgement
and control solution for autonomous vehicle corresponding to atypical driving
environment,” which is financed from the Ministry of Science and ICT
(Republic of Korea) Contract No. 2019-0-00399. The students are supported
by the BK21 FOUR from the Ministry of Education (Republic of Korea).
1
Hyungtae Lim,
1
Minho Oh, and
1
Hyun Myung are with the School of
Electrical Engineering, KI-AI, KI-R at KAIST (Korea Advanced Institute
of Science and Technology), Daejeon, 34141, South Korea. {shapelim,
minho.oh, hmyung}@kaist.ac.kr
GLE
Concentric Zone Model Output of GLE
Ground
Estimate
3D scan
For each bin
R-GPF
Fig. 1. Overview of our proposed method called Patchwork.
Patchwork mainly consists of three parts: Concentric Zone
Model (CZM)–based polar grid representation, Region-wise
Ground Plane Fitting (R-GPF), and Ground Likelihood Esti-
mation (GLE).
successful navigation. The other purpose, on which this paper
places more emphasis, is the segmentation of a point cloud
to recognize or track moving objects. Terrestrial vehicles or
humans inevitably come into contact with the ground [14];
ideally, dynamic objects can be recognized in a simple way,
such as through Euclidean clustering if the ground is well
estimated [8], [15]. Furthermore, because most cloud points
belong to the ground, ground segmentation can significantly
reduce computational power when one is performing object
segmentation or detection in a preprocessing stage [16]. Thus,
ground in this study refers to not only the road, which is a
movable area, but also all regions that moving objects can
come into contact with, including sidewalks or lawns.
In this study, as presented in Fig. 1, we propose a novel
Concentric Zone Model (CZM)–based region-wise ground
segmentation method, called Patchwork, which is an extension
of Region-wise Ground Plane Fitting (R-GPF) in our previous
study [14]. The aim of R-GPF in our previous study was to
estimate the ground points for static map building purposes,
whereas here, we focus only on ground segmentation on a
3D point cloud. We also conduct detailed experiments on the
impact of the bin size, which was not covered in our previous
paper.
In summary, the contribution of this paper is threefold:
• To the best of our knowledge, it is the first attempt to
analyze the impact of bin size when estimating ground
planes in complex urban environments using the Se-
manticKITTI dataset [1]. Accordingly, an efficient, non-
uniform, region-wise representation of a 3D point cloud
is proposed, referred to as a CZM–based representation
whose bin size is different depending on each zone.
• Also, we leverage Ground Likelihood Estimation (GLE)
in terms of uprightness, elevation, and flatness to deter-
arXiv:2108.05560v2 [cs.RO] 10 Mar 2022