Control unit and a method for managing a machine

Abstract

A method for managing a machine in a terrain comprising one or more slopes is provided The method comprises obtaining (201) terrain data indicative of the terrain. The method comprises determining (202) a set of tracks based on the terrain data. Each track comprises respective trajectories determined to be traversable by the machine, and wherein each respective trajectory is determined to account for a rollover hazard associated with the one or more slopes. The method comprises determining (203) a set of connections connecting the set of tracks. Each connection out of the set of connections is indicative of a respective trajectory for the machine for transitioning between respective tracks in the set of tracks. The method comprises determining (204) a path for the machine to follow in the terrain. The path is determined based on the determined set of tracks and the determined set of connections.

Description

TECHNICAL FIELD Embodiments herein relate to a control unit and a method therein. Furthermore, a vehicle comprising the control unit, a computer program and a carrier are also provided herein. In some aspects, embodiments herein relate to handling a machine configured to perform one or more agricultural and / or silvicultural operations in a terrain comprising one or more slopes. BACKGROUND Using an automated machine to perform agricultural such as farming and / or silvicultural operations such as forestry management is complex and involves a difficulty to plan an efficient path for the machine, especially if the terrain to be traversed is irregularly formed or comprises difficult terrain. One way to determine a path is to first establish mostly parallel tracks, which are typically manually set based on a shape of the terrain to be traversed by the machine, and where connections between the tracks are set at the end of the tracks based on a predetermined turning radius. A path can further be determined based on any suitable path finding algorithm over the established tracks and connections. However, if the terrain is rough or comprises too many steep slopes and obstacles, it may not be possible for the machine to traverse all of the tracks and connections. In these situations, the machine may get stuck due to risk of rolling over in steep slopes if the machine traverses inclines or declines of the slope at a hazardous angle, and the machine may then need human intervention to continue travelling or may simply risk rolling over. To avoid these situations, a path may instead be determined to avoid rough terrains comprising slopes and obstacles thereby leading to a very inefficient path but which is much easier for an automated machine to follow without encountering problems. SUMMARY An object of embodiments herein is to improve efficiency of handling a machine configured to perform one or more agricultural and / or silvicultural operations in a terrain comprising one or more slopes. Silvicultural operations herein may comprise any one or more suitable operations related to forestry, such as planting one or more tree plants and / or inspecting the environment of the terrain, when the terrain comprises woods and / or forest. According to a first aspect of embodiments herein, a method for managing a machine in a terrain comprising one or more slopes is provided. The machine is configured to perform one or more agricultural and / or silvicultural operations in the terrain. The method comprises obtaining terrain data indicative of the terrain and the one or more slopes therein. The method further comprises determining a set of tracks based on the terrain data. Each track comprises respective trajectories between respective positions in the terrain. Each respective trajectory is determined to be traversable by the machine between the respective positions. Each respective trajectory is determined to account for a rollover hazard associated with the one or more slopes. The method further comprises determining a set of connections for the set of tracks. Each connection out of the set of connections is indicative of a respective trajectory for the machine to follow for transitioning between respective tracks in the set of tracks. The method further comprises determining a path for the machine to follow in the terrain. The path is determined based on the determined set of tracks and the determined set of connections. According to a second aspect of embodiments herein, a control unit configured to manage an machine in a terrain is provided. The machine is configured to perform one or more agricultural and / or silvicultural operations in the terrain. The control unit is configured to obtain terrain data indicative of the terrain and the one or more slopes therein. The control unit is configured to, based on the terrain data, determine a set of tracks. The set of tracks is determined to comprise tracks. Each track comprises respective trajectories between respective positions in the terrain. Each respective trajectory is determined to be traversable by the machine between the respective positions. Each respective trajectory is determined to account for a rollover hazard associated with the one or more slopes. The control unit is configured to determine for the set of tracks, a set of connections. Each connection out of the set of connections being indicative of a respective trajectory for the machine to follow for transitioning between respective tracks in the set of tracks. The control unit is configured to, based on the determined set of tracks and the determined set of connections, determining a path for the machine to follow in the terrain. It is furthermore provided herein a computer program comprising instructions, which, when executed on at least one processor, cause the at least one processor to carry out the methods above. It is additionally provided herein a carrier, having stored thereon a computer program product comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the methods above. It is furthermore provided, a machine configured to perform one or more agricultural and / or silvicultural operations in a terrain comprising one or more slopes. The machine may is comprise, or arranged to be remotely controlled by, the control unit according to the second aspect. Since the set of tracks is determined to comprise traversable trajectories and account for a rollover hazard associated with the one or more slopes, a more efficient path can be determined. This is since the machine is now enabled to use paths in complex and otherwise hazardous terrain environments. This is since when the set of tracks are determined to be traversable and to account for rollover hazards, the set of tracks will be determined such that they only allow for safe trajectories over the one or more slopes such as by ensuring that the machine do not use tracks which would involve a hazardous angles related to lateral or longitudinal inclinations or declinations of the one or more slopes. It follows that the machine can operate using an increased number of tracks of the terrain, which further means that the determined path will further be more efficient such as covering more areas of the terrain when determining the path to have increased path coverage. BRIEF DESCRIPTION OF THE DRAWINGS Examples of embodiments herein are described in more detail with reference to attached drawings in which: Figs. 1 a-c Fig. 2 are schematic block diagrams illustrating example embodiments herein, is a flowchart depicting an example method according to embodiments herein. Figs. 3a-b Fig. 4 Figs. 5a-c Fig. 6 Fig. 7 Fig. 8 is a diagram illustrating example embodiments herein. is a diagram illustrating example embodiments herein. are diagrams illustrating example embodiments herein. is a diagram illustrating example embodiments herein. is a diagram illustrating example embodiments herein. is a schematic block diagram illustrating embodiments of a control unit. DETAILED DESCRIPTION Embodiments herein may provide aspects for improving efficiency of agriculture and / or silviculture automation by enabling machines to use paths in rough terrain in an efficient manner. Figs. 1a-c are schematic overview depicting non-limiting examples of embodiments herein. Figs. 1a-c illustrate a representation of a terrain 100 and a machine 1 arranged to operate in the terrain 100. The terrain 100 may comprise forest or woods and / or may comprise any suitable entities related with agriculture such as farming, and / or silviculture such as forestry. As illustrated in Fig. 1a, the terrain 100 may comprise one or more slopes 60. While indicated as rectangular areas in Fig. 1 a, and in other illustrations of embodiments herein, the one or more slopes 60 may comprise any slopes with irregular inclinations and / or declinations of any angle, such as natural irregularities of inclinations found in forests or woods. In the terrain 100, machines may operate, such as the machine 1. The machine 1 is configured to perform one or more agricultural and / or silvicultural operations in the terrain 100 such as planting one or more plants, e.g., tree plants such as tree saplings, transported by the machine 1 and / or by inspecting trees or plants found in the terrain 100. The machine 1 may be any suitable machine for performing the one or more agricultural and / or silvicultural operations in the terrain 100. For example, the machine 1 may be a tree plantation vehicle and / or a tree inspection vehicle. Alternatively, the machine 1 may be a farming vehicle. The machine 1 may be an autonomous vehicle. In embodiments herein, the machine 1 may or may not transport an operator. The machine 1 may be an articulated machine comprising a trailer carrying one or more plants and / or a planting equipment. The one or more plants may be tree saplings. To determine a path, as will be discussed in embodiments herein, a set of tracks 10 is determined, as illustrated in Fig. 1a. Each track out of the set of tracks 10 comprises respective trajectories between respective positions in the terrain 100. Each respective trajectory is determined to be traversable by the machine 1 between the respective positions. Each respective trajectory is determined to account for a rollover hazard associated with the one or more slopes 60. Each track in the set of tracks 10 may be selected to be followed by the machine 1, e.g., as part of determining a path. According to embodiments herein, a set of connections 20 may connect the set of tracks 10. Each connection out of the set of connections 20 may be indicative of a 5 respective trajectory for the machine 1 to follow for transitioning between respective tracks in the set of tracks 10. In other words, to transition between following a first track in the set of tracks 10 to a second track in the set of tracks 10, a connection in the set of connections 20 may be intermediately followed for transitioning the machine 1 into following the second track. The set of tracks 10 may typically be disjoint with respect to each other, and instead may be connected by the set of connections 20. The terrain 100 may further comprise one or more obstacles 40. The one or more obstacles 40 may be any suitable object or obstacle which the machine 1 cannot, or should not, e.g., due to danger or hazards, traverse. For example, the one or more obstacles may comprise any one or more out of: - One or more trees, - one or more stones or boulders, e.g., with a size greater than a threshold, - one or more lake areas or water areas, e.g., with a depth greater than a threshold, - one or more swamps, - one or more residential areas, and - one or more restricted areas. Embodiments herein may be controlled by a control unit 80. The control unit 80 may be a control unit comprised in the machine 1 or remote to the machine 1, e.g., in a server or remote cloud environment. The control unit 80 may be communicatively coupled with, e.g., wired or wirelessly, to control and / or to communicate with any one or more entities of the machine 1, e.g., any one or more out of sensors, actuators, vehicle motions controllers, or other controllers. To perform the one or more agricultural and / or silvicultural operations, the control unit 80 may be communicatively coupled with, e.g., wired or wirelessly, to control and / or to communicate equipment attached to the machine 1 such as plant handling equipment, robot arms for grabbing and / or planting trees, cameras for inspecting plants and / or the environment surrounding the machine 1. In other words, the machine comprises, or is arranged to be remotely controlled by, the control unit 80. As illustrated as an example in Fig. 1b, the set of tracks 10 and the set of connections 20 may be used to determine a path 50 as part of embodiments herein as will further be discussed with respect to Fig. 2. The path 50 may be a selection of tracks and connections out of the set of tracks 10 and the set of connections 20 to form the path, e.g., based on any suitable heuristics such as for improving path coverage of the machine 1 in the terrain 100. The path 50 may or may not comprise loops, i.e., cycles where tracks in the set of tracks 10 are used multiple times. The path 50 may typically comprise a predefined or dynamically set start position 21, i.e., a position in, or in proximity to a first track in the set of tracks 10. The path 50 may comprise an end position 22, e.g., as part of a track in the set of tracks 10. The path 50 may be determined before the machine 1 is travelling in the terrain 100, i.e., before performing the one or more agricultural and / or silvicultural operations in the terrain 100. The path 50 may however also be dynamically determined as the machine 1 travels on the path 50. In these embodiments, no end position 22 is predetermined and the machine 1 may be configured to travel until reaching some termination condition, e.g., planting a set number of plants, or based on when the machine 1 needs maintenance, recharging or refueling. As illustrated in Fig. 1c, the set of tracks 10 and / or the set of connections 20 may be determined by accounting fora rollover hazard of the machine 1 as also further discussed with respect to Fig. 2. For example, the machine 1 may be restricted to travelling on a slope in the one or more slopes 40 with a lateral angle for inclination or declination, which is at most a predefined lateral angle 61, e.g., 20 degrees. Additionally, or alternatively, the machine 1 may be restricted to travelling on a slope in the one or more slopes 40 with a longitudinal angle for inclination or declination, which is at most a predefined longitudinal angle 62, e.g., 25 degrees. In other words, the set of tracks 10 and / or the set of connections 20 may be determined to account for rollover hazards or other stability hazards based on the knowledge of where the machines 1 may traverse the terrain, and / or based on limitations of lateral and / or longitudinal angles the machine 1 can tolerate with respect to the terrain 100. A number of embodiments will now be described, some of which may be seen as alternatives, while some may be used in combination. Fig. 2 illustrates an example method for managing the machine 1 in the terrain 100. The terrain 100 comprises the one or more slopes 60. The machine 1 is configured to perform one or more agricultural and / or silvicultural operations in the terrain 100 such as planting one or more plants in the terrain and / or inspecting forestry or other environment in the terrain 100. The control unit 80 may perform the method as described below. The method comprises the following actions, which actions may be taken in any suitable order. Optional actions are indicated with dashed boxes in Fig. 2. Action 201 The method comprises obtaining terrain data indicative of the terrain 100 and the one or more slopes 60 of the terrain 100. The terrain data may be predefined, measured by previous machines travelling in the terrain 100 and / or received from a server. The terrain data may comprise any suitable information which may affect how the machine will or can travel the terrain 100, e.g., any one or more out of: - an indication of inclinations and / or declinations and associated angles of the one or more slopes, - one or more inputs, e.g., from a user, indicative of at least one boundary area, - topology of the terrain 100, - an indication of the one or more obstacles 40, - an indication of one or more geofences where the machine 1 cannot travel, e.g., as part of the one or more obstacles 40. Action 202 The method comprises determining the set of tracks 10 based on the terrain data. Each track out of the set of tracks 10 comprises respective trajectories between respective positions in the terrain 100. Each respective trajectory is determined to be traversable by the machine 1 between the respective positions. Each respective trajectory is determined to account for a rollover hazard associated with the one or more slopes 60. The set of tracks 10 may be determined to have a set width or a set minimum width, e.g., which width or minimum width may correspond to a size and / or characteristics of the machine 1. Since the rollover hazard is accounted for, the set of tracks 10 are safe for the machine 1 to travel. To account for the rollover hazard, heuristics and / or embodiments as discussed below may be used to ensure that rollover hazards are avoided or mitigated. For example, determining the set of tracks 10 may comprise validating that the set of tracks 10 does not relate to a rollover hazard, such as validating that the machine 1, if following the set of tracks 10, or a specific track therein, in the one or more slopes 60, will not exceed the predefined lateral angle 61 and / or the predefined longitudinal angle 62. Determining the set of tracks 10 may further comprise validating that the machine 1, if following the set of tracks 10 or a specific track therein, will not collide with or attempt to travel over the one or more obstacles 40. Other embodiments herein may implicitly account for the rollover hazard by aligning tracks along track directions without obstacles or positions in slopes associated with rollover risk for the machine 1. Establishing respective preferred track directions for the set of tracks 10 In some embodiments, determining the set of tracks 10 may comprise establishing respective preferred track directions for a plurality of positions in the terrain 100. The preferred track directions may respectively be represented as a respective angle for a respective position with respect to a predefined direction, e.g., “north”. The preferred track directions may respectively guide a direction for determining a track of the set of tracks 10 that is to go through, or in proximity to the respective position of a respective preferred track direction. The preferred track directions may be established by, evaluating respective distances the machine 1 is capable of traversing the terrain 100 for a plurality of directions from each respective position in the plurality of positions. The plurality of directions is typically as many as possible, as they improve accuracy for determining the preferred track direction which in the end improves track generation. However, the plurality of directions may be at least 6 or 8 in number, often more than that, such as 16 number of directions. The respective distances may relate to an estimation of how far the machine can travel in a respective direction until reaching a position where the machine 1 cannot travel any further in the respective direction, e.g., due to the one or more obstacles 40 and / or due to rollover hazards of the machine 1 in the one or more slopes 60. The estimation of the respective distances may be based on the terrain data and optionally a predefined model of the machine 1. In other words, evaluating the respective distances may comprise accounting for whether the machine 1 is capable of safely traversing respective inclines and / or declines of the one or more slopes 60 in the terrain 100. Establishing the preferred track directions may further comprise, for each respective position in the plurality of positions, establishing a respective preferred track direction for a respective position based on the evaluated distances. The respective track direction may for example be determined based on the longest one or more evaluated distances out of the evaluated distances. Additionally or alternatively, the respective track direction may be determined by taking into account distances below a set threshold, i.e., which may correspond to non-preferred track directions. Additionally or alternatively, the respective preferred track direction may be based on a length of the evaluated distances such that the respective track directions is based on predefined heuristics of the directions associated with the evaluated distances. The predefined heuristics may consider a trend in direction associated with the evaluated distances such that the respective preferred track direction is established for a direction which is associated with the distances above a threshold which are in similar directions. In other words, a trend in track directions may be determined using the evaluated distances. The trend may determine the respective preferred track direction. The trend may be determined by letting multiple or all orthogonal pairs of directions of the plurality of directions form respective pair of vectors based on their respective evaluated distance from a respective position. Each pair of vectors are scored based on a length of a resulting scalar product of the respective vectors. The resulting scalar product with the highest score, i.e., greatest scalar product, may be considered the trend and the respective vectors may be used in combination, e.g., an average vector of the two or any suitable derivation, as the preferred track direction for a respective position. In some embodiments, establishing the preferred track directions further comprises applying a smoothening and / or filtering function to one or more of the preferred track directions. For example, preferred track directions may respectively be compared with track directions of adjacent positions and adjusted by a predefined coefficient to have a direction more similar to the compared track direction. In some embodiments, establishing the preferred track directions is further based on one or more inputs, e.g., from a user, indicative of at least one boundary area. In these embodiments, the at least one boundary area may represent different areas of the terrain 100, and establishing the preferred track directions may be performed for each of them separately. The respective edges of the at least one boundary area may in these embodiments act as an obstacle in terms of evaluating distances for each respective position. For example, determining the set of tracks 10 may comprise determining the set of tracks 10 based on the established preferred track directions. In some embodiments, the set of tracks 10 may be determined to at least partly align with the established preferred track directions. In other words, the set of tracks 10 may be determined to comprise at least one track which, for one or more positions, connects the respective preferred track directions to form the at least one track. Determining the set of tracks 10 based on the established preferred track directions may imply that the rollover hazard is accounted for, as the machine 1 travelling along the preferred track directions will not risk rolling over, or the risk is significantly reduced. Track determination using simulation In some embodiments, determining the set of tracks 10 comprises simulating a movement of a set of particles in a representation of the terrain 100. Each particle in the set of particles may typically be represented as a circle but other shapes may also apply. In other words the set of particles may be abstract representations used to find tracks. Each particle in the set of particles may be associated with any one or more out of: a predefined shape, a size ora bounded collision area such as a collision radius, mass, kinetic energy, velocity, speed, direction, angular momentum, and elasticity. The most important constant parameters for the simulation may be mass, angular momentum, elasticity. In these embodiments, each particle in the set of particles comprises two respective poles. The two respective poles may be areas or positions of the respective particle. The two respective poles may be located on opposite sides of the respective particle. The simulation may be based on a simulation configuration. The simulation configuration may define one or more parameters for how to simulate the set of particles with respect to a representation of the terrain 100, and with respect to the established preferred track directions. The simulation configuration may further indicate any one or more out of the following parameters: a number of particles in the set of particles, an initial distribution of particles with a settable density, and a velocity configuration of the set of particles, such as a random configuration wherein the set of particles are initialized with random velocities, i.e., random direction,d magnitude, and orientation. The set of particles may be simulated during a time period to move and interact with a set kinetic energy with respect to the representation of the terrain 100. The simulation may comprise simulating a first force applied to the set of particles to follow the established preferred track directions. The magnitude of the first force may be based on the simulation configuration. In other words, the first force may apply to the set of particles such as to rotate respective particles to align the respective poles with one or more track directions of the established preferred track directions. The simulation may comprise simulating a second force, for respective two poles of different particles in the set of particles to attract each other. In other words, the second force may apply to the set of particles such as to push and / or rotate respective particles such that respective poles of different particles are attracted, i.e., moved and / or rotated, towards each other. The simulation may comprise simulating a third force, for respective collisions of the set of particles with each other or simulated obstacles of the terrain 100. The third force may apply a repelling or deterring force to a respective particle with respect to a collision point of the respective particle. The simulation may be initialized by applying kinetic energy, i.e., movement in any direction, for particles in the set of particles. The simulation allows for the set of particles to attract respective poles, and for the poles to align the established preferred track directions in a dynamic manner. The simulation may terminate when forces applied to the set of particles meet a termination condition such that a kinetic energy of the set of particles is below a threshold or is zero. In other words, a simulated kinetic energy sum simulated for the set of particles is allowed to gradually decrease as the set of particles move and interact, and the simulation stops after a fixed number of iterations at a threshold of kinetic energy of the simulated set of particles. This may be referred to as a cooling process which may happen simultaneously so that stable structures are forming, and may be part of a simulated annealing process. In response to terminating the simulation, e.g., with respect to the termination condition, the method comprises determining the set of tracks 10 based on forming tracks by connecting respective poles between particles in the set of particles. Connecting the respective poles for the set of particles may thereby form a number of chains of connected particles where the respective particles have aligned to the established preferred track directions and the connected respective poles. Determining the set of tracks 10 may thereby comprise determining tracks to traverse positions associated with the particles and / or poles of the number of chains of connected particles. Determining the set of tracks may further comprise validating the set of tracks based on one or more criteria of turning radius and / or rollover hazard, e.g., to ensure that the machine 1 will not roll over or experience any other hazard, and / or additionally to ensure that the machine 1 can perform said turning radius. In other words, at the end of the simulation, a number of poles of the set of particles will have found positions where they are at least partly aligned with the established preferred track directions and further may be in proximity to at least one other pole of another particle, e.g., within a predefined distance. The set of tracks 10 may be determined as trajectories traversing positions of the terrain 100 associated with respective particles in the set of particles. Trajectories of the set of tracks 10 may be formed based on positions of the respective poles of the respective particles. The trajectories may be formed in many different ways, such as directly connected between the poles, but the trajectories may also be formed to have smoother trajectories, e.g., by forming trajectories based on center positions associated with the set of particles, and positions in-between, e.g., in the middle of a distance between, two closest poles of different respective particles. Any suitable method to form the trajectories between the particles with closest adjacent poles may be used, as if the trajectory aligns with the poles of the particles, the resulting trajectory will be characterized in following the terrain 100 such that the preferred track directions are accounted for, which also means that rollover risk is mitigated or removed. Track determination using an iterative function In some embodiments, determining the set of tracks 10 comprises assigning respective values for each position associated with a respective track direction of the established preferred track directions. The values may be any suitable values, e.g., between 0-1. The assigned values may be represented by any suitable mathematical model, e.g., as a set of pixels and / or as a matrix, i.e., where each position of the matrix may be a pixel which value corresponds to a color, e.g., from 0 to 1 being mapped from black to white. Each respective value may be assigned as a constant or assigned as a value from a predefined distribution interval, e.g., by a randomization function. In some embodiments, determining the set of tracks 10 comprises iteratively applying a function. The applying of the function comprises updating each assigned value of a position based on the assigned respective values of one or more adjacent positions of the respective assigned value based on a filter, e.g. a Gabor filter. The filter may indicate coefficients, e.g., positive or negative, which shall be applied to the respective assigned values of the one or more adjacent positions. The coefficients may be based on which filter is used, and which filter to use may be determined based on which preferred track direction is associated with the current position and assigned value to be updated. In other words, each position has an assigned value, and the respective assigned value is updated based on its current value, and based on its respective preferred track direction, and based on the assigned values of the one or more adjacent positions. The one or more adjacent positions may be any suitable number of adjacent positions, and may not necessarily be directly adjacent. For example, if the positions are represented as pixels or values in a matrix, then a value to be updated may be in a center position, and the adjacent positions may be values or pixels a number of rows or columns below, above, or to the side of the number to be updated. In edges of such a matrix, any suitable edge case calculation may apply. As an example, determining the set of tracks 10 may comprise iteratively performing the function for finding positions which are associated with aligned track directions that can be grouped for determining tracks to be part of the set of tracks 10. The function may comprise updating the assigned value at each position based on the assigned values and based on preferred the track direction at the position of the respective assigned value. In other words, each position may have an assigned value, and it is updated based on the preferred track direction of its associated the position and based on the assigned value of the position together with the assigned values of one or more adjacent positions. Based on a predefined function, the assigned value of the position may increase or decrease. The assigned values may be arranged as a matrix with respect to their respective positions and respective preferred track direction. The function iteratively applied may then be a function applying a selective convolution to the matrix. In the selective convolution, a kernel matrix is selected individually at each position, based on the preferred track direction at each position. The kernel matrix may be or relate to a Gabor filter selected from a set of Gabor filters based on the respective preferred track direction of the positions which value is to be updated. Updating each assigned value using the function may be iterated until a terminating condition, typically a set number of iterations. Each iteration may comprise updating each value of each position. Updating each assigned value using the function may form one or more aligned groups of positions. Each aligned group of positions may comprise associated values within a respective target interval such as above a threshold. If the associated values are within the respective target interval, then it may mean that they have been found to be associated with directions such that they can be used together to determine tracks to be part of the set of tracks 10, i.e., the directions of each position may align within some error margin. The aligned group of positions may indicate different areas or patterns which may be used to determine where tracks can be formed. Hence, determining the set of tracks 10 may further be based on the one or more aligned groups of positions. Action 203 The method comprises determining a set of connections 20 connecting the set of tracks 10. As an example, each connection out of the set of connections 20 may be indicative of a respective trajectory for the machine 1 to follow for transitioning between respective tracks in the set of tracks 10. The set of connections 20 may connect the tracks in the set of tracks 10 at endpoints of a respective track, or at any other suitable position of a respective track. The set of connections 20 may connect the set of tracks 10 such that the set of tracks 10 and the set of connections 20 form multiple interconnected trajectories throughout the terrain 100, which trajectories the machine 1 can follow in any suitable manner, e.g., as part of an autonomous mode of the machine 1. In some embodiments, determining the set of connections 20 comprises determining a set of candidate connections between the set of tracks 10. The set of candidate connections may be generated based on any suitable generation method between a number of different positions of different tracks in the set of tracks 10. The set of candidate connections may comprise connections between positions of different tracks of the set of tracks 10 of up to a predefined connection distance, e.g., in each direction such that the respective candidate connection may represent a connection in different directions. Typically, the set of candidate connections may be two-dimensional and predetermined trajectories which are then evaluated based on the rollover hazard if applied to the terrain 100, e.g., with respect to the one or more slopes. Determining the set of connections 20 may further be based on the determined set of candidate connections, e.g., by selecting one or more traversable connections for the machine 1 to use for transitioning between following different tracks in the set of tracks. In some embodiments determining the set of connections 20 comprises validating the set of candidate connections based on whether they are traversable by the machine 1 at least with respect to traversing respective one or more declines and / or inclines of one or more slopes 60. In other words, only candidate connections which comprise declines and / or inclines within the boundaries of the predefined lateral angle 61 and / or the predefined longitudinal angle 62 may be considered validated. Validating the set of candidate connections may further be performed with respect to the one or more obstacles 40, e.g., such that only candidate connections which are traversable such that the one or more obstacles are not in the way for the machine 1 may be considered validated. In some embodiments, only validated candidate connections may be determined to be part of the set of connections 20. Validating the set of candidate connections may further comprise evaluating the set of candidate connections based on one or more lateral and / or longitudinal angles of the respective candidate connections and with respect to the predefined lateral angle 61 and / or the predefined longitudinal angle 62. If exceeding the predefined lateral angle 61 and / or the predefined longitudinal angle 62, the candidate connections are not valid to use for the machine 1. A predetermined cost function may relate to estimating a traversing metric of how well, or if, the machine 1 can travel a respective candidate connection based on predefined heuristics. Validating the set of candidate connections or evaluating traversing metrics thereof for validating said candidate connections may be based on said cost function. In some embodiments, the method comprises, for each pair of tracks in the set of tracks 10, determining the set of connections 20 by selecting validated candidate connections above a traversing metric, typically at least one per pair of tracks in the set of tracks 10. The set of connections 20 may be determined to comprise trajectories which have a set width or a set minimum width, e.g., which width or minimum width may correspond to a size and / or characteristics of the machine 1. In other words, the trajectories may adhere to a size of the machine 1. Action 204 The method comprises determining the path 50 for the machine 1 to follow in the terrain 100. The path 50 is determined based on the determined set of tracks 10 and the determined set of connections 20. The path 50 may be at least partly determined by selecting tracks and connections out of the set of tracks 10 and the set of connections 20, e.g., based on any strategy and / or heuristic(s). The path 50 may comprise the start position 21. The path 50 may or may not comprise the end position 22, e.g., such as depending on whether the path is determined dynamically, as the machine 1 is travelling the path 50, or not. Determining the path 50 may be performed at any suitable time, before or during the machine is travelling the path 50. The same may apply to any one or more out of actions 201,202, 203. Determining the path 50 may comprise iteratively selecting tracks out of the set of tracks 10 and connections out of the set of connections 20 to form the path 50. The path 50 may be determined to have cycles, e.g., the path 50 may indicate to use some tracks of the set of tracks 10 multiple times. The path 50 may be determined to indicate an order of how the machine 1 shall follow the tracks and connections forming part of the path 50. The path 50 may be determined using any suitable heuristics and / or path searching strategy with respect to the set of tracks 10 and the set of connections 20. In some embodiments, determining the path 50 comprises using a predetermined path search strategy. For example, determining the path 50 may comprise, from the start position 21, selecting tracks and connections out of the set of tracks 10 and set of connections 20 to form the path 50 for the machine 1 to follow. In some embodiments, determining the path 50 comprises determining the path 50 in the terrain 100 by using a path coverage algorithm with respect to the set of tracks 10. The path coverage algorithm may comprise selecting tracks and / or connections from the set of tracks 10 and the set of connections 20, such that as much as possible of the terrain 100 will be traversed by the machine 1. The path coverage algorithm may further comprise conditioning the selection of set of tracks 10 and the set of connections 20 to occurrences of cycles in the determined path 50 such that each track in the set of tracks 20 can only occur a predetermined number of times in the path 50The minimum distance requirement may be useful to ensure that if the machine 1 is planting one or more plants along the path 50, then the plants will have sufficient distance to the other plants. The minimum distance requirement may therefore be based on a predetermined plant parameter based on which type(s) of plant(s) is / are to be planted along the path 50. In some embodiments, determining the path 50 comprises assessing whether or not including at least a part of at least one first candidate track in the set of tracks 10 increases a coverage of the path 50 in the terrain 100 as compared to including at least a part of at least one second candidate track in the set of tracks 10. In other words, determining the path 50 may be part of an iterative path searching methodology, where next one or more trajectories to be part of the path 50 are evaluated based on heuristics and compared to one or more alternatives of one or more respective alternative trajectories. As discussed above, determining the path 50 may comprise iteratively selecting tracks out of the set of tracks 10 based on one or more heuristics. The one or more heuristics may be predefined. The path 50 may be determined from the start position 21 by selecting a track out of the set of tracks 10 and / or a connection out of the set of connections 20 based on the one or more heuristics, and iteratively selecting a subsequent track out of the set of tracks 10 and / or a subsequent connections out of the set of connections 20 based on the one or more heuristics. The one or more heuristics may comprise any one or more out of: • Selecting a track and / or connection out of the set of tracks 10 and / or out of the set of connections 20 based on path coverage of the terrain 100. This means that each track or connection may be selected based on trying to cover as much ground or area as possible. • Selecting a track and / or connection out of the set of tracks 10 and / or out of the set of connections 20 based on number of occurrences of said track in the path 50. Reducing the number of occurrences of tracks and / or connections in the path may improve fuel / energy efficiency and may ensure that an increased area of the terrain 100 is covered given a maximum distance the machine 1 can travel, compared to iteratively using same tracks multiple times. • Selecting a track and / or connection out of the set of tracks 10 and / or out of the set of connections 20 based on a number of adjacent connections or tracks and their respective occurrences in the path. This allows the path 50 to be determined such as to select tracks and / or connections previously not selected as part of the path 50, thereby improving path coverage. This is recursive for a number of tracks and connections. • Selecting a track and / or connection out of the set of tracks 10 and / or out of the set of connections 20 based on choosing a highest scoring candidate with respect to maximizing covering as much ground or area visited for the first time in the terrain 100. • Selecting a track and / or connection out of the set of tracks 10 and / or out of the set of connections 20 based on a path searching or graph traversal strategy, such as A*, D*, postman related algorithms, travelling salesman related algorithms, or any other suitable method. • Selecting a track and / or connection out of the set of tracks 10 and / or out of the set of connections 20 based on reaching positions and / or areas most distant from the start position 21, e.g., to quicker reach non-explored areas for improved path coverage. The one or more heuristics as discussed above may be combined in any suitable manner. In some embodiments, determining the path 50 is further based on a reaching capability of the machine 1 to plant one or more plants carried by the machine 1. The reaching capability may relate to how far the machine 1 can reach to plant a plant such as a tree plant when travelling the path 50, such that the path 50 can be determined such that the machine 1 can reach a maximum number of positions of the path 50. Action 205 In some embodiments, the method comprises triggering the machine 1 to travel the determined path 50. Alternatively, the method comprises triggering the machine 1 to travel the determined path 50, and to perform the one or more agricultural and / or silvicultural operations in the terrain 100. Alternatively, the method comprises triggering the machine 1 to travel the determined path 50, and to perform the one or more agricultural and / or silvicultural operations in the terrain 100 when travelling the path 50. The one or more agricultural and / or silvicultural operations may for example comprise planting one or more plants, e.g., tree saplings, along or in proximity to the path 50 as the machine 1 follows the path 50. The path 50 may further indicate positions of where to plant the one or more plants, or the machine 1 may dynamically detect suitable positions within the path 50 or within a range of the path 50 as the machine 1 travels along the path 50. Triggering the machine 1 to travel the determined path 50, and to perform the one or more agricultural and / or silvicultural operations in the terrain 100 when travelling the path 50 may further comprise triggering the machine 1 to schedule and / or perform one or more planting operations along the path 50, such that the machine 1 does not traverse a plant planted by the machine 1 in the path 50, e.g., by iterating the use of a track in the set of tracks 10. In other words, if a position is to be travelled multiple times in the path 50 and is subject to plant a plant, then the plant is planted when travelling the positions for the last time. In other words, triggering the machine 1 to travel the determined path 50 comprises triggering a planting equipment of the machine 1 to perform a tree planting procedure. Triggering the planting equipment of the machine 1 to perform the tree planting procedure may comprise using a robot arm of the machine 1 to plant one or more plants. Triggering the planting equipment of the machine 1 to perform the tree planting procedure may comprise triggering to plant tree plants such that a tree plant is planted in a track out of the set of tracks 10, the last time the machine 1 is travelling said track when travelling along said path 50. The above embodiments will now be further explained and exemplified below. The embodiments below may be combined with any suitable embodiment above. Fig. 3a illustrates an example of establishing a first preferred track direction 300 for a first position 310 of the plurality of positions in the terrain 100, e.g., as also discussed in action 202. In the example scenario of Fig. 3a, respective distances 330 from the first position 310 are evaluated by estimating, e.g., based on the terrain data as obtained in action 201, how far the machine 1 can travel in the plurality of directions until it either would collide with the one or more obstacles 40, or would be at risk of rolling over due to travelling in the one or more slopes 60 at a hazardous angle, e.g., exceeding the predefined lateral angle 61 and / or the predefined longitudinal angle 62. The first preferred track direction 300, e.g., as part of the preferred track directions discussed in action 202, may then be established with respect to the distance traversable in each of the plurality of directions, e.g., a measure of a trend or a common direction. Fig. 3b illustrates another example of establishing a first preferred track direction 300 for a first position 310. In this example, a Vector V is rotated in four steps along the plurality of directions with the respective evaluated distances 330. Four steps are used in the example, but in practical implementations, more rotations and directions in the plurality of directions may be used. The steps may be referred to as V0, V1, V2, and V3, with respective rotation angles 0, 45, 90, and 135 degrees. For every angle of rotation, the following sum may be calculated: all scalar products between Vi and lines Pi, are added to a respective sum, where Pi is expressed as vectors. From the respective sum, scalar products of all lines Pi and VPi are subtracted, where VPi is a vector orthogonal to Vi. The Vi rotation angle which corresponds to a trend may be used to form the preferred track direction 300. The trend may be the greatest sum, after subtraction as discussed above. A pseudo algorithm for selecting the vector to be used as base for the preferred track direction is illustrated in Algorithm 1. For all angles i: score = 0 For all lines j : score = score + dot(Pj,Vi) - dot(Pj, VPi) At all angles i, choose the vector Vi which has the best score to represent the preferred track direction, or to be used as a basis to determine the preferred track direction. Algorithm 1. Fig. 4 illustrates a representation of the terrain 100 with preferred track direction 400 illustrated by a number of arrows in different directions, e.g., as preferred track directions discussed in action 202. The preferred track directions 400 may comprise preferred track directions established in the same manner as the first preferred track direction 300, but for a different location in the terrain 100. Using the preferred track directions 400, a set of tracks 410 may be determined by aligning the respective tracks along respective track directions of preferred track directions 400. The set of tracks 410 may be part of the set of tracks 10. Fig. 5a-c illustrates examples of simulating the set of particles, e.g., as in action 202 for determining the set of tracks 10. Fig. 5a illustrates an example set of particles 510, e.g., as used in action 202 for simulating the set of particles. The set of particles 510 may comprise a virtual representation of particles, typically as a circle shape, but other shapes may also apply. The set of particles 510 may respectively comprise at least two poles 520. The at least two poles 520 may respectively be positioned on predefined areas of a respective particle of the set of particles 510. Fig. 5b illustrates a representation of the terrain 100 with preferred track direction 500 illustrated by a number of arrows in different directions, e.g., as preferred track directions discussed in action 202. The preferred track directions 500 may be the same or similar as the preferred track directions 400 as discussed above. The set of particles 510 is simulated in the representation of the terrain 100. Each particle may be initiated with a force or movement, e.g., spin, rotation, velocity, etc. Each of the at least two poles 520 of the set of particles 510 may attract to another respective pole 520, e.g., as a simulated force. Each of the at least two poles 520 of the set of particles 510 may align with the preferred track directions 500, e.g., as a simulated force. The set of particles may collide and / or bounce with each other and / or the terrain 100 causing a simulation of one or more colliding forces which moves the set of particles 510. After a termination condition, e.g., when all particles in the set of particles 510 have stopped moving, the simulation is considered completed and tracks can be formed. Fig. 5c illustrates a representation of the set of particles 510 in a representation of the terrain 100 after the simulation, e.g., as in action 202, has terminated. A set of tracks 550 are determined by connecting trajectories via the at least two poles 520 of the set of particles. Each track in the set of tracks 550 may be determined by a trajectory based on positions of both poles, or their average position, of a first respective particle in the set of particles 510, and further based on a position of a first pole of the respective first particle to a position of a closest pole of another particle which closest pole is within a predefined distance of the first pole in the representation of the terrain 100. If forming the trajectory directly between the poles as in Fig. 5c, sharp turns 555 may emerge which may be difficult for the machine 1 to travel. This may be solved by forming the trajectory using a smoothing function. The smoothening function may form the trajectory based on a middle position between the respective poles and an average position of each particle. In this way, the set of tracks 550 may naturally be formed to align with the preferred track directions 500. The set of tracks 550 may be part of the set of tracks 10, e.g., as simulated in actions 202. Fig. 6 illustrates track determination using the iterative function, e.g., as in action 202. The iterative function may be applied to assigned values of the plurality of positions of the terrain 100. The plurality of positions may be associated with the preferred track directions, e.g., the preferred track directions 400 and / or the preferred track directions 500 as discussed above, such that each position corresponds to a preferred track direction. Each position is in Fig. 6 comprises an assigned value illustrated as a respective pixel according to an initial state 600-0. The assigned values may have been randomized or set in any suitable manner. The pixels may correspond to the respective assigned values. Due to only using black and white coloring, the pixels may indicate a high value, e.g., above a threshold and low values e.g., below a threshold. Black or white may indicate any of the low or high values. The assigned values may be updated by applying the iterative function. The function may for each pixel use the value of said pixel, and surrounding pixels as a sub-matrix 601. Based on the preferred track direction of the position of the pixel to be updated, a Gabor filter is selected. The Gabor filter 602 is selected from a set of filters wherein the set of filters are associated with different angles of direction, and the selected Gabor filter may be the filter closest in angle with respect to the preferred track direction of the position of the pixel to be updated, in this example, the respective preferred track direction is closest to a 22.5 degree angle, and the Gabor filter 602 related to the 22.5 degree angle is selected. The Gabor filter 602 and the sub-matrix 601 is of the same size such that each value or pixel of the Gabor filter 602 may indicate for each corresponding value or pixel of the sub-matrix 601, a coefficient indicating if the corresponding value of the sub-matrix 601 shall increase or decrease the pixel to be updated. Typically all values of the sub-matrix 601 is multiplied by the corresponding value of the corresponding position of the Gabor filter 602, and further summed to the value of the pixel to be updated. This behavior is performed for each pixel in the matrix 600-0, demanding a new selection of Gabor filter per pixel. Typically an activation function or thresholding function may be applied, or alternatively least a clamping function which limit the sum to a range. The process is iterated for each pixel for multiple iterations, in this example we illustrate the result after, one iteration 600-1, two iterations 600-2, five iteration 600-5, ten iterations 600-10, twenty iterations 600-20, fifty iterations 600-50, and finally 100 iterations 600-100 which in this scenario is considered the final iteration. In the final matrix of iteration 600100, it can clearly be seen that a pattern of the pixels have emerged. The pattern may correspond to the aligned groups of positions as discussed in action 202, i.e., as each pixel corresponds to a value and position associated with a preferred track direction. The patterns may emerge due to common or complying characteristics of track directions of different positions. This means that the patterns of high and / or low values may be used to form tracks in the set of tracks 10, e.g., by aligning tracks 610 in areas formed by the patterns in the final matrix of iteration 600-100. Fig. 7 illustrates a set of candidate connections 710, e.g., as in action 203, which may be generated at least partly in the one or more slopes 60 of the terrain 100. The set of candidate connections 710 may be generated based on any suitable generation method between any suitable combination of positions 710 of different tracks in the set of tracks 10. While only candidate connections connecting two tracks in the set of tracks 10 are illustrated in Fig. 7, it shall be noted that the set of candidate connections may further apply to any number of tracks in the set of tracks 10, wherein each track of the set of tracks 10 has a generated candidate connection in the set of candidate connections 710 if they are within a predefined connection distance of each other. The set of candidate connections 710 may be validated based on one or more predefined models of the machine 1 and based on the terrain data, e.g., as obtained in action 201. For example, it may be simulated or estimated how the machine 1 would traverse the respective candidate connections 710, and if possible to traverse the respective candidate connection without estimating a risk for a rollover of the machine 1, the respective candidate connection may be considered validated. The set of candidate connections 20 may further be formed based on the validated set of candidate connections 710. To perform the method actions above, the control unit 80 is configured to manage the machine 1 in the terrain 100. The machine 1 is configured to perform one or more agricultural and / or silvicultural operations in the terrain 100. The control unit 80 is illustrated in Fig. 8. The components of the control units 80 may be directly integrated into the machine 1 in any suitable manner. In other words, while Fig. 8 illustrates the control unit 80, the illustration may also be for the machine 1, e.g., as a single entity. The control unit 80 may also be comprised in a remote location from the machine 1, e.g., as part of a server and / or a cloud service. The control unit 80, may comprise an input and output interface 800 configured to communicate with and / or to control entities of the machine 1, e.g., sensor, actuators, and / or plant handling equipment. The input and output interface 800 may e.g., comprise a wired or wireless receiver (not shown) and a wireless or wired transmitter (not shown). The control unit 80 is further configured to obtain terrain data indicative of the terrain 100 and the one or more slopes 60 therein. The control unit 80 is further configured, based on the terrain data, determine a set of tracks 10. Each track out of the set of tracks 10 comprises respective trajectories between respective positions in the terrain 100. Each respective trajectory is determined to be traversable by the machine 1 between the respective positions, and wherein each respective trajectory is determined to account for a rollover hazard associated with the one or more slopes 60. The control unit 80 is further configured to determine a set of connections 20 connecting the set of tracks 10. The control unit 80 is further configured to, based on the determined set of tracks 10 and the determined set of connections 20, determining a path 50 for the machine 1 to follow in the terrain 100. In some embodiments, the control unit 80 is further configured to determine the set of tracks 10 by: - establishing respective preferred track directions 300, 400, 500, 600 for a plurality of positions in the terrain 100 by: o for each respective position in the plurality of positions, evaluating respective distances 330 the machine 1 is capable of traversing the terrain 100 for a plurality of directions from the respective position, and o establishing a respective preferred track direction 300, 400, 500, 600 for the respective position based on the evaluated distances. In some embodiments, the control unit 80 is further configured to evaluate the respective distances 330 by accounting for whether the machine 1 is capable of safely traversing respective inclines and / or declines of the one or more slopes 60 in the terrain 100. In some embodiments, the control unit 80 is further configured to establish the preferred track directions 300, 400, 500, 600 by applying a smoothening and / or filtering function to one or more of the preferred track directions 300, 400, 500, 600. In some embodiments, the set of tracks 10 is determined to at least partly align with the established preferred track directions 300, 400, 500, 600. In some embodiments, the control unit 80 is further configured to determine the set of tracks 10 by: - simulating a movement of a set of particles 510 in a representation of the terrain 100, each particle in the set of particles comprises two respective poles 520, and wherein the set of particles 510 is simulated during a time period to move and interact with a set kinetic energy with respect to the representation of the terrain 100, with a simulated first force applied to the set of particles 510 to follow the established preferred track directions 300, 400, 500, 600, and with a simulated second force for the respective two poles 520 of different particles in the set of particles 510 to attract each other, and - in response to terminating the simulation, determining 202 the set of tracks 10 based on forming tracks by connecting respective poles 520 between particles in the set of particles 510. In some embodiments, the control unit 80 is further configured to determine the set of tracks 10 by: - assigning respective values for each position associated with a respective track direction of the established preferred track directions 300, 400, 500, 600, and - iteratively applying a function which comprises updating each assigned value based on the assigned respective values and based on preferred track directions 300, 400, 500, 600 of one or more adjacent positions of the respective assigned value, to form one or more aligned groups of positions 610 each comprising associated values within a respective target interval such as above a threshold, and - determining the set of tracks 10 based on the one or more aligned groups of positions 610. In some embodiments, the control unit 80 is further configured to determine the set of connections 20 by: -  determining a set of candidate connections 710 between the set of tracks 10, - validating the set of candidate connections 710 based on whether they are traversable by the machine 1 at least with respect to traversing respective one or more declines and / or inclines of one or more slopes 60, and - determining the set of connections 20 by evaluating the validated connections based on the predetermined cost function. In some embodiments, the control unit 80 is further configured to determine the path 50 by using a predetermined path search strategy, and to determine the path 50 by, from a start position 21, select tracks and connections out of the set of tracks 10 and set of connections 20 to form the path 50 for the machine 1 to follow. In some embodiments, the control unit 80 is further configured to determine the path 50 by determining the path 50 in the terrain 100 by using a path coverage algorithm with respect to the set of tracks 10. In some embodiments, the control unit 80 is further configured to determine the path 50 by assessing whether or not including at least a part of at least one first candidate track in the set of tracks 10 increases a coverage of the path 50 in the terrain 100 as compared to including at least a part of at least one second candidate track in the set of tracks 10. In some embodiments, the control unit 80 is further configured to determine the path 50 further based on a reaching capability of the machine 1 to plant one or more plants carried by the machine 1. In some embodiments, the control unit 80 is further configured to trigger the machine 1 to travel the determined path 50, and to perform the one or more agricultural and / or silvicultural operations in the terrain 100 when travelling the path 50. The embodiments herein may be implemented through a respective processor or one or more processors, such as the processor 860 of a processing circuitry in the control unit 80, together with respective computer program code for performing the functions and actions of the embodiments herein. The program code mentioned above may also be provided as a computer program e.g., a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the control unit 80,. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server and downloaded to the control unit 80, The control unit 80, may further comprise a memory 870 comprising one or more memory units. The memory 870 comprises instructions executable by the processor in the control unit 80. The memory 870 is arranged to be used to store e.g. information, indications, data, configurations, and applications to perform the methods herein when being executed in the control unit 80. In some embodiments, a computer program 880 comprises instructions, which when executed by the respective at least one processor 860, cause the at least one processor of the control unit 80, to perform the actions above. In some embodiments, a respective carrier 890 comprises the respective computer program 880, e.g., as part of the control unit 80, wherein the carrier 890 is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium. Those skilled in the art will appreciate that the units in the control unit 80, described above may refer to a combination of analog and digital circuits, and / or one or more processors configured with software and / or firmware, e.g. stored in the plant handling arrangement 1, e.g., the control unit 80, that when executed by the respective one or more processors such as the processors described above. One or more of these processors, as well as the other digital hardware, may be included in a single ApplicationSpecific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a system-on-a-chip (SoC). When using the word "comprise" or “comprising" it shall be interpreted as nonlimiting, i.e. meaning "consist at least of". 5 The embodiments herein are not limited to the above described preferred embodiments. Various alternatives, modifications and equivalents may be used. Any embodiments and / or examples mentioned above may be used in any suitable combination with any other one or more embodiments and / or examples above.

Claims

1. A method for managing a machine (1) in a terrain (100) comprising one or more slopes (60), wherein the machine (1) is configured to perform one or more agricultural and / or silvicultural operations in the terrain (100), the method comprising:- obtaining (201) terrain data indicative of the terrain (100) and the one or more slopes (60) therein,- based on the terrain data, determining (202) a set of tracks (10), wherein each track out of the set of tracks (10) comprises respective trajectories between respective positions in the terrain (100), wherein each respective trajectory is determined to be traversable by the machine (1) between the respective positions, and wherein each respective trajectory is determined to account for a rollover hazard associated with the one or more slopes (60),- determining (203) a set of connections (20) connecting the set of tracks (10),- based on the determined set of tracks (10) and the determined set of connections (20), determining (204) a path (50) for the machine (1) to follow in the terrain (100).

2. The method of claim 1 wherein determining (202) the set of tracks (10) comprises:- establishing respective preferred track directions (300, 400, 500, 600) for a plurality of positions in the terrain (100) by:o for each respective position in the plurality of positions, evaluating respective distances (330) the machine (1) is capable of traversing the terrain (100) for a plurality of directions from the respective position, ando establishing a respective preferred track direction (300, 400, 500, 600) for the respective position based on the evaluated distances.

3. The method of claim 2, wherein evaluating the respective distances (330) comprises accounting for whether the machine (1) is capable of safely traversing respective inclines and / or declines of the one or more slopes (60) in the terrain (100).

4. The method of any of claims 2 - 3, wherein establishing the preferred track directions (300, 400, 500, 600) further comprises applying a smoothening and / or filtering function to one or more of the preferred track directions (300, 400, 500, 600).

5. The method of any of claims 2-4 wherein the set of tracks (10) is determined to at least partly align with the established preferred track directions (300, 400, 500, 600).

6. The method of any of claims 2-5 wherein determining (202) the set of tracks (10) comprises:- simulating a movement of a set of particles (510) in a representation of the terrain (100), each particle in the set of particles comprises two respective poles (520), and wherein the set of particles (510) is simulated during a time period to move and interact with a set kinetic energy with respect to the representation of the terrain (100), with a simulated first force applied to the set of particles (510) to follow the established preferred track directions (300, 400, 500, 600), and with a simulated second force for the respective two poles (520) of different particles in the set of particles (510) to attract each other, and- in response to terminating the simulation, determining (202) the set of tracks (10) based on forming tracks by connecting respective poles (520) between particles in the set of particles (510).

7. The method of any of claims 2-5 wherein determining (202) the set of tracks (10) comprises:- assigning respective values for each position associated with a respective track direction of the established preferred track directions (300, 400, 500, 600), and- iteratively applying a function which comprises updating each assigned value based on the assigned respective values and based on preferred track directions (300, 400, 500, 600) of one or more adjacent positions of the respective assigned value, to form one or more aligned groups of positions (610) each comprising associated values within a respective target interval such as above a threshold, and- determining the set of tracks (10) based on the one or more aligned groups of positions (610).

8. The method of any of claims 1-6 wherein determining (203) the set of connections (20) comprises:-  determining a set of candidate connections (710) between the set of tracks (10),-  validating the set of candidate connections (710) based on whether they aretraversable by the machine (1) at least with respect to traversing respective one or more declines and / or inclines of one or more slopes (60), and- determining the set of connections (20) by evaluating the validated connections based on a predetermined cost function.

9. The method of any of claims 1-8 wherein determining the path (50) comprises using a predetermined path search strategy, wherein determining the path (50) comprises, from a start position (21), selecting tracks and connections out of the set of tracks (10) and set of connections (20) to form the path (50) for the machine (1) to follow.

10. The method of any of claims 1-9 wherein determining the path (50) comprises determining the path (50) in the terrain (100) by using a path coverage algorithm with respect to the set of tracks (10).

11. The method of any of claims 1-10 wherein determining the path (50) comprises assessing whether or not including at least a part of at least one first candidate track in the set of tracks (10) increases a coverage of the path (50) in the terrain (100) as compared to including at least a part of at least one second candidate track in the set of tracks (10).

12. The method of any of claims 1-11 wherein determining the path (50) is further based on a reaching capability of the machine (1) to plant one or more plants carried by the machine (1).

13. The method of any of claims 1-12, further comprising triggering (205) the machine (1) to travel the determined path (50), and to perform the one or more agricultural and / or silvicultural operations in the terrain (100) when travelling the path (50).

14. A control unit (80) configured to manage an machine (1) in a terrain (100), wherein the machine (1) is configured to perform one or more agricultural and / or silvicultural operations in the terrain (100), the control unit (80) being configured to:- obtain terrain data indicative of the terrain (100) and the one or more slopes (60) therein,- based on the terrain data, determine a set of tracks (10), wherein each track out of the set of tracks (10) comprises respective trajectories between respective positions in the terrain (100), wherein each respective trajectory is determined to be traversable by the machine (1) between the respective positions, and whereineach respective trajectory is determined to account for a rollover hazard associated with the one or more slopes (60),- determine a set of connections (20) connecting the set of tracks (10),- based on the determined set of tracks (10) and the determined set of connections (20), determining a path (50) for the machine (1) to follow in the terrain (100).

15. A control unit (80) according to claim 14, further configured to perform the method according to any of claims 1-13.

16. A machine (1) configured to perform one or more agricultural and / or silvicultural operations in a terrain (100) comprising one or more slopes (60), wherein the machine (1) is comprising, or is arranged to be remotely controlled by, the control unit (80) according to any of claims 14 or 15.

17. The machine (1) of claim 16, wherein the machine (1) is a tree planting machine (1).

18. The machine (1) of claim 17, wherein the machine (1) is an autonomous vehicle configured to perform one or more planting operations in the one or more slopes (60) of the terrain (100).

19. A computer program comprising instructions, which when executed by a processor, causes the processor to perform actions according to any of the claims 1-13.

20. A carrier comprising the computer program of claim 19, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

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