Fields2Cover An open-source coverage path planning library for unmanned agricultural vehicles Gonzalo Mier1João Valente2Sytze de Bruin3

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Fields2Cover: An open-source coverage path planning library for
unmanned agricultural vehicles
Gonzalo Mier1João Valente2Sytze de Bruin3
Abstract This paper describes Fields2Cover1, a novel open
source library for coverage path planning (CPP) for agricul-
tural vehicles. While there are several CPP solutions nowadays,
there have been limited efforts to unify them into an open
source library and provide benchmarking tools to compare their
performance. Fields2Cover provides a framework for planning
coverage paths, developing novel techniques, and benchmarking
state-of-the-art algorithms. The library features a modular and
extensible architecture that supports various vehicles and can
be used for a variety of applications, including farms. Its
core modules are: a headland generator, a swath generator,
a route planner and a path planner. An interface to the Robot
Operating System (ROS) is also supplied as an add-on. In
this paper, the functionalities of the library for planning a
coverage path in agriculture are demonstrated using 8 state-
of-the-art methods and 7 objective functions in simulation and
field experiments.
Keywords – Agricultural Automation, Software Architecture
for Robotic and Automation, Field Robots
I. INTRODUCTION
In developed countries, there is a shortage of skilled
workers to operate agricultural machinery [1]. This shortage
can be alleviated with the development of autonomous ma-
chinery. Unlike manually operated machinery, autonomous
vehicle operations need meticulous planning beforehand. The
problem of determining a path to cover a field is known as
coverage path planning (CPP). CPP is of high importance
for cleaning [2], surveillance robots [3], lawn mowers [4],
and agricultural vehicles [5], where it has been addressed in
several works.
Whilst there have been many efforts, most of the (par-
tial) CPP solutions have not been released as open-source
software thus hindering more rapid advances in CPP by the
scientific community. The packages shown in Table Iare
the only open-source software to the best of our knowledge.
Note that the software packages listed in Table Isolve the
CPP problem partially, but require several modifications in
order to be customized to different unmanned vehicles and
applications.
This paper aims to fill the above mentioned gap by
proposing and releasing to the community an open-source
CPP library for field coverage. The library was designed
1Gonzalo Mier with the Laboratory of Geo-Information Science and
Remote Sensing, Wageningen University & Research, Wageningen, The
Netherlands gonzalo.miermunoz@wur.nl
2João Valente with the Information Technology Group, Wageningen
University & Research, Wageningen, The Netherlands
3Sytze de Bruin with the Laboratory of Geo-Information Science and
Remote Sensing, Wageningen University & Research, Wageningen, The
Netherlands
1https://github.com/Fields2Cover/Fields2Cover
focusing in four modules that are the core of CPP solutions: a
headland generator, a swath generator, a route planner, and a
path planner. Each module includes at least one state-of-the-
art method and one objective function. The library currently
only supports convex fields on arable farmland. Regardless,
there is an urgent need for an open source software solution
to fill the existing gap in the CPP problem in agriculture.
The ultimate goal of the library is to ease the state of-the-
art algorithm benchmark and to accelerate CPP research and
application.
A. Related work
Owing to the non-holonomous nature of agricultural ve-
hicles, a region of the field known as headlands must be
reserved for turning the vehicle. The most basic approach
is to allocate a constant width area around the field. This
strategy allocates a large amount of space to a poor yield
area. Depending on how the swaths are arranged, some
headland areas are parallel to the swaths and hence they
are not needed for turning. By only constructing headlands
along the field edges where turns are made, the area reserved
for them can be minimized [5], [17].
Swaths are generated in the inner field, which is the
remaining region after subtracting the headlands. In two-
dimensional planar fields, a reference line can be applied as
a guide for the generation of swaths, where each parallel
creates a swath [5], [17], [18]. This line can be chosen
for convenience or by an algorithm such as brute force
or a meta-heuristic. Oksanen [5] describes a driving angle
search strategy that requires fewer iterations than brute force
search but it does not guarantee finding the global minimum.
Objective functions such as the number of turns or the sum
of swath lengths are used to determine optimality in swath
generation [17].
The distance [17] and time [19] required to cover the
field are affected by the order of the swaths. A route is the
sequence of the swaths to cover. The Boustrophedon order,
which travels the swaths sequentially from one side of the
field to the other, and the snake order, which skips one swath
at each turn and returns through the uncovered swaths, are
popular preset routing patterns [20]. Objective functions such
as distance, number of rotations, or time necessary to traverse
the field [17], [19] are minimized by finding the optimal route
through meta-heuristics [21].
A path is composed of the swaths of a route connected
by turns, forming a continuous line along which the vehicle
will drive. Dubins’ [22] or Reeds-Shepp’s [23] curves are
turns that minimize the path length of the turns. These
arXiv:2210.07838v2 [cs.RO] 17 Feb 2023
TABLE I: Comparison between coverage path planning open-source software solutions. Repositories (rows) are compared in
terms of (1) available documentation (Docs); (2) Computation of exact solutions rather than using a discretizing grids (No
grid); (3) Support for non-holonomous vehicles in turns; (4) The option to reserve maneuvering space at the field boundaries
(Headlands support); (5) The possibility to modify the objective function; (6) Applicability for agricultural ground robots.
Package name Docs No grid
used
Non-
holonomous
Headlands
support
Customizable
objective
function
Terrestrial
agricultural
vehicles
RJJxp/CoveragePlanning [6] 747 7 7 7
Nobleo/full_coverage_path_planner [7] 4747 7 7
Ipa320/ipa_coverage_planning [2], [8], [9] 4 4 4 7 7 7
Ethz-asl/polygon_coverage_planning [10], [11] 4 4 7 7 7 7
Irvingvasquez/ocpp [12], [13] 747 7 7 7
Greenzie/boustrophedon_planner [14] 74 4 4 7 7
Ipiano/coverage-planning [15], [16] 4 4 7 7 47
Fields2Cover 4 4 4 4 4 4
curves are made by either curve segments or straight lines.
The main problem is that there is an instantaneous change
of curvature at the transition point between two segments.
Techniques such as numerical integrators [24] or clothoids
[25] are employed to smooth the turn to avoid the curvature
discontinuity. Furthermore, to navigate from a swath to
the headlands, turns such as non-uniform rational B-spline
(NURBS) curves [26] can be adopted.
CPP problems are composed of numerous sub-problems,
several of which have received special attention in literature.
For example, Spekken [21] presents an approach for calcu-
lating the coverage path in undulating terrain that however
does not consider turns between rows or headland creation.
Nilsson [27] and Nørremark [28] divide the CPP problem
into two major modules: Field Partitioning/Representation,
where the distribution of headlands and swaths in the field
is set up, and Route Planning, which determines the opti-
mal order of travelling the swaths within sub-fields. In the
latter framework, each module has more than one function,
increasing the complexity of comparing multiple variations
of the module.
B. Existing open-source software
There have been web applications, such as GAOS [18],
that allowed farmers to design or adapt coverage paths with
a user-friendly interface. Many of such web applications,
despite being a great help to the farming community, have
been developed in collaboration with companies, restricting
the possibility to release the code to the public domain.
The currently existing open source CPP repositories are
listed in Table I. Although seven other projects were found,
none of them can be adopted for farming purposes with
ground robots. As mentioned above, ground robots in agri-
culture are generally non-holonomous, so turning maneuvers
must be planned to move from one swath to another. Unfor-
tunately, some packages [6], [10], [12], [15] only compute
the route to cover a region. These packages are designed
for quadrotors [10], [12] or for indoor robots [6]. However,
the code needs to be modified to support path generation
for non-holonomous robots. A special case of CPP is the
Nobleo package [7] which, although the vehicle used is non-
holonomous, uses a grid to define the nodes that should
be covered at least once. In agriculture it is important to
reduce the damage caused by the wheels of the vehicle,
so it is not recommended to cover the same swath several
times [7] or to cross through the main field [6], [8], [10].
On the other hand, Greenzie [14], which was developed for
lawn mowers, is the only package that supports headlands,
along with Fields2Cover. Unlike arable farming, mowers are
constrained to avoid repeated tracks for field traffic, thus
the coverage path is created with random sweep angles. For
this reason, Greenzie does neither provide an optimizer nor
an objective function for planning the swaths. In contrast,
Ipiano [15] provides an interface to change the objective
function used by its optimizer, but here no headland support
is offered. Fields2Cover is the only software solution that
provides algorithms to create a coverage path for terrestrial
agricultural robots, including optimizers and objective func-
tions to generate the best path, headland support and turn
planning.
C. Contributions
The main contributions of this paper and the Fields2Cover
library are:
1) A publicly-available library (Fields2cover) providing
connectable modules to address CPP problems with
unmanned agricultural vehicles. Those modules can be
effortlessly customized for other CPP problems.
2) Benchmark tools for quantitative comparison between
the CPP algorithms and approaches.
3) A quantitative comparison using 38 convex fields be-
tween eight state-of-the-art CPP approaches/methods
and seven objective functions.
4) Experiments with a commercial unmanned agricul-
tural vehicle demonstrating Fields2Cover’s capability
to provide real-world solutions.
5) Contribute to building a research community by pro-
viding an accessible platform for discussing novel
ideas, solving issues and sharing new variants of the
problem.
摘要:

Fields2Cover:Anopen-sourcecoveragepathplanninglibraryforunmannedagriculturalvehiclesGonzaloMier1JoãoValente2SytzedeBruin3Abstract—ThispaperdescribesFields2Cover1,anovelopensourcelibraryforcoveragepathplanning(CPP)foragricul-turalvehicles.WhilethereareseveralCPPsolutionsnowadays,therehavebeenlimitede...

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