Method for detecting the soil level on an area to be worked by an agricultural machine

Description

[0001] The present invention relates to a method for detecting the ground level on a surface to be worked by an agricultural working machine according to the preamble of claim 1. Furthermore, the present invention relates to an agricultural working machine for carrying out such a method according to claim 13.

[0002] Methods and systems for detecting the ground level and / or the stand heights of plants are known from the documents DE 10 2011 017621 A1, DE 10 2011 085380 A1, EP 3 530 099 A1 and EP 3 530 098 A1.

[0003] The determination of the crop height of a field using an optical sensor array mounted on an agricultural machine, which determines distances using the time-of-flight method, is carried out using a static transformation related to the mounting position of the sensor array. The sensor array is usually located at the highest point of the machine, the cab roof. Starting from this point in the sensor array, from which electromagnetic transmission beams are emitted and reflected transmission beams are received, the crop height is determined. This method of determining the crop height is prone to errors due to the lack of inclusion of the soil contour in the area observed by the sensor array. An undulating soil structure that deviates from a uniform, level soil contour leads to different crop heights.If a cutting edge or a tramline is present, this effect can be slightly compensated but not nearly completely eliminated by ground level detection next to the crop, i.e. in the area of ​​the cutting edge or the tramline.

[0004] The invention is therefore based on the object of developing a method of the type mentioned at the outset, by means of which the detection of the ground level is improved and the determination of the stand height is thus made more precise.

[0005] The above object is achieved in a method according to the preamble of claim 1 by the features of the characterizing part of claim 1. Furthermore, this object is achieved from a device-technical perspective based on the preamble of claim 13 in conjunction with its characterizing features. The dependent claims following therefrom respectively represent advantageous developments of the invention.

[0006] According to claim 1, a method for detecting the ground level on an area to be worked by an agricultural work machine is proposed, wherein the work machine comprises a sensor arrangement by means of which transmission pulses from electromagnetic transmission beams are periodically emitted in at least one transmission direction onto the area to be worked, wherein the transmission pulses are reflected by a field crop and soil as reflection surfaces and received as echo pulses by the sensor arrangement and transmitted to a control unit of the work machine for evaluation, wherein for at least some of the transmission pulses emitted by the sensor arrangement designed as a laser scanner, different partial beams of one and the same transmission beam are reflected with a time offset from one another by reflection surfaces located in the respective transmission direction, so that the respectively resulting echo pulse is composed of correspondingly time-shifted partial echo pulses.According to the invention, it is provided that the ground level and / or a crop height of the field crop is determined by means of the control unit based on a pulse width within the resulting echo pulse and / or a pulse shape of the resulting echo pulse as well as a runtime-based distance determination of a distance value to the respective reflection surface.

[0007] The fundamental idea is that by processing and evaluating the temporal signal shape of the echo pulses provided by the sensor array designed as a laser scanner, a distinction is made between the crop and the ground as reflection surfaces. The ground level of the ground on which the crop to be harvested is located is detected as the reflection surface. Detecting the ground level at which the crop to be harvested is located enables a more precise determination of the actual crop height. The method according to the invention determines the respective ground level that occurs at the location where the crop whose crop height is being determined is located.

[0008] Using areas adjacent to the crop to be harvested, such as a cutting edge or a lane, cannot reflect the actual ground level. Particularly due to the large working widths of attachments mounted on agricultural machinery, any changes in the ground contour compared to a previously harvested adjacent lane are not detected. The method according to the invention avoids this disadvantage by proactively determining the ground level.

[0009] In particular, by processing and evaluating the temporal signal shape of the echo pulses provided by the sensor array designed as a laser scanner, it is possible to distinguish between plants of different crop types. Depending on the crop type cultivated on an area to be treated, the respective crop height varies significantly. The method should be carried out depending on the crop type. In a corn field, the distance between the ridge line of the crop and the ground is greater than, for example, in rapeseed or wheat fields.

[0010] For this purpose, a distinction can be made between different crop types in the existing field using a measure of scatter in the reflection height and / or the signature of the pulse shape by comparing it with reference curves. Preferably, the reference curves can be stored in a memory unit of the control unit for retrieval. However, it is also conceivable that the reference curves can be retrieved from an external data source.

[0011] A variance, a standard deviation or a quantile, in particular a 10% quantile, can be used as a measure of dispersion in order to distinguish between crop types in the vicinity of the working machine.

[0012] In particular, the differentiation between different crop types can be carried out based on the pulse width relative to a predetermined threshold for an accumulation of measured values ​​in a spatially limited segment within the field.

[0013] Preferably, the impact on the field crop can be determined based on a first rising edge of the respective resulting echo pulse and the impact on the ground can be determined based on a last falling edge of the resulting echo pulse.

[0014] For this purpose, the stand height and the position of the ground level can be determined based on a time offset between the first rising edge and the last falling edge of the respective resulting echo pulse for an accumulation of measured values ​​in a segment within the field stand.

[0015] In particular, based on the detection of at least the ground level, at least one action instruction can be generated by the control unit to influence the operation of the work machine. Furthermore, the crop height, which is detected in particular optionally, can be used to generate an action instruction by the control unit that influences the operation of the work machine. For example, the detection can be used for predictive height control of an attachment mounted on the work machine. In particular, the detection of the ground level can be used to control the cutting height of a header attached to the work machine. The detection of the ground level can also be used to set or adjust the travel speed of the work machine.

[0016] Furthermore, at least one instruction can be implemented as a specification and / or a selection of initial operating parameters for at least one working unit of the agricultural work machine. In particular, the at least one working unit can be an attachment or an implement of a work machine designed as a self-propelled harvester or as a tractor.

[0017] Preferably, the reflection intensity of the respective resulting echo pulse, the wavelength and / or ambient light conditions can be determined by the laser scanner. For this purpose, the laser scanner can be configured to provide signals which, in addition to the pulse width and / or the pulse shape, i.e. the temporal signal shape of the echo pulses, enable an evaluation of the reflection intensity, existing ambient light conditions and / or the wavelength of the reflected transmission pulses. The surface color and / or surface roughness of the reflection surfaces can be determined using the reflection intensity. The evaluation of the wavelength can also be used to determine the surface color and / or surface roughness of the reflection surfaces. Furthermore, the composition of the reflection surfaces can be deduced from the wavelength of the reflected transmission pulses.This allows the determination of the type and position of the reflection surfaces to be further improved or refined.

[0018] According to a further development, at least one additional optical sensor arrangement other than a laser scanner can be used to classify the crop type and / or foreign growth. The inclusion of an additional optical sensor arrangement that is not designed as a laser scanner can contribute to improving the analysis process for classifying the crop type. For example, a camera can be provided as the optical sensor arrangement, which generates images in the visible spectral range. Alternatively, a camera can be provided as the optical sensor arrangement, which generates images in the near-infrared range. The classification result can be improved by including RGB camera images or infrared camera images as well as additional specific characteristics of the crop and / or foreign growth, such as shape, color, structure, and the like.

[0019] Statistical or adaptive thresholding methods, or non-analytical methods, can preferably be used to analyze the resulting echo pulse. Examples include Gaussian elimination, support vector machines, or artificial neural networks, which can be used to perform classification.

[0020] According to a teaching according to claim 13, which has independent significance, an agricultural work machine, in particular a self-propelled harvester or a tractor, for carrying out the proposed method is claimed as such. Reference may be made to all statements regarding the proposed method that are suitable for explaining the work machine.

[0021] Preferably, the laser scanner can be implemented as a solid-state LiDAR, a Geiger-mode LiDAR, a scanning LiDAR, or a single-photon LiDAR. These LiDAR sensors are characterized by high resolution, which improves the unambiguous assignment of the temporal signal shape of the echo pulses, for example, using conventional static or adaptive thresholding methods or artificial neural networks.

[0022] The present invention is explained in more detail below with reference to an embodiment shown in the drawings.

[0023] They show: Fig. 1 a working machine for carrying out a proposed method with a sensor arrangement during the harvesting of a field a) in a side view and b) in a plan view, Fig. 2 the field according to Fig. 1 in a view along the direction of travel of the working machine; Fig. 3a) a transmission pulse of the sensor arrangement according to Fig. 1and b) the resulting echo pulse of a plant assigned to the transmitted pulse; Fig. 4a) two separate partial echo pulses and b) two superimposed partial echo pulses; Fig. 5a) an example of a cross-section of height values ​​of a crop of a corn field and b) an example of an echo pulse shape of a crop reflection of corn plants and a ground reflection of a soil as the respective reflection surface; and Fig. 6a example of a cross-section of height values ​​of a crop of a rapeseed field and b) an example of an echo pulse shape of a crop reflection of rapeseed plants and a ground reflection.

[0024] The Fig. 1The proposed working machine 1 shown, which is designed as a self-propelled harvesting machine, is used to cultivate an agricultural area 25, here the harvesting of a field 2 on the area 25, which consists of a plurality of plants 3. The plants 3 of the field 2 are located on a field soil 4, as also shown in the illustration. Fig. 1 can be seen. The work machine 1 can also be designed as a tractor with an attached or towed attachment.

[0025] During harvesting, the field crop 2 is located in front of the working machine 1 in the direction of travel 5 of the working machine 1. Seen from the working machine 1, the frontmost plants 3a and the plants 3b inside the crop exist.

[0026] The work machine 1 has a control unit 6 and a sensor arrangement 7, wherein, by means of the sensor arrangement 7, transmission pulses 8 from electromagnetic transmission beams are periodically emitted in at least one transmission direction 10 onto the crop 2. The transmission pulses 8 are reflected by the crop 2 or the plants 3 as well as by the underlying soil 4 and received as echo pulses 11 by the sensor arrangement 7. The plants 3 and the soil 4 form reflection surfaces RF.

[0027] A summary of the Fig. 1 and Fig. 2 shows that for at least some of the transmission pulses 8, different partial beams 12, 13 are reflected from plants 3a, 3b of the field 2 lying one behind the other in the respective transmission direction 10 with a time delay. The reason for this is that the partial beam 13 in Fig. 1a) must travel an additional path, namely twice the path ΔE, compared to partial beam 12. The time offset is calculated by dividing the additional path by the propagation speed of the transmitted beam 9.

[0028] Fig. 2 shows that the transmitted beam 9 on the plant 3a is assigned a measuring spot M, which is defined by the beam cross-section of the transmitted beam 9. The plants 3 of the field 2 are here and preferably equipped with ears 14, wherein the ear 14a of the front plant 3a causes the reflection of the first partial beam 12, while the ear 14b of the rear plant 3b causes the reflection of a second partial beam 13.

[0029] The representation of the transmitted beam 9 and the partial beams 12, 13 in the drawing represents an idealized situation. In a real environment, a multitude of partial beams 12, 13 usually result from one and the same transmitted beam 9, to which the proposed basic principle applies analogously. Therefore, all statements regarding partial beams 12, 13 apply accordingly to all other partial beams that may occur.

[0030] Fig. 2 shows that the beam cross-section of the transmitted beam 9 must have a certain minimum extension in order to enable the proposed multiple reflection of the transmitted beam 9. Here, and preferably, the transmitted beam 9 forms a rounded beam cross-section at the foremost plants 3a with respect to the respective transmission direction.

[0031] In plants 3 with elongated ears 14, the measuring spot is preferably designed such that the transmission beam 9 can radiate past the respective ear 14. In detail, it is preferably the case that the plants 3 form elongated ears 14 with a mean width 19, wherein the transmission beam 9 on the ears 14 of the foremost plants 3a with respect to the respective transmission direction 10 is assigned a measuring spot M due to its beam cross section, the diameter 20 of which is at least in one direction larger, in particular at least twice larger, than the width 19 of the ears 14. This relationship is in Fig. 2 indicated schematically. Fig. 2 further shows that the measuring spot M' forms an exempted area 21 in the area of ​​the plant 3b inside the stand, which results from the reflection of the partial beam 12, i.e. from the resulting radiation.

[0032] From the time-shifted reflection of the partial beams 12, 13 it follows that the resulting echo pulse 11 is composed of correspondingly time-shifted partial echo pulses 11a, 11b, as shown in the illustration according to Fig. 3 This shows Fig. 3a ) first the transmission pulse 8, which is sent by the sensor arrangement 7 in a transmission direction 11 to the field crop 2. In Fig. 3a ) the transmission pulse 8 is represented by its light power I over time t.

[0033] The representation in Fig. 3b ) shows a resulting echo pulse 11 of one of the plants 3, which is assigned to the transmission pulse 8. A corresponding representation of the resulting echo pulse 11 can be found in Fig. 3b). Here, it can be seen that the resulting echo pulse 11 is composed of correspondingly time-shifted partial echo pulses 11a, 11b. In the illustrated embodiment, this means that the resulting echo pulse 11 results from an addition of the two partial echo pulses 11a, 11b. The time offset ΔT V corresponds to the above-mentioned time required by the transmission beam 9 to travel the distance ΔE twice. From the Fig. 3b ) shows that the two partial echo pulses 11a, 11b merge into one another in the time domain. Depending on the structure of the field 3, however, it may also be the case that the partial echo pulses 11a, 11b are separated from one another in the time domain.

[0034] A summary of the Fig. 1 , Fig. 2 and Fig. 3shows that the distance ΔE, which is also referred to here as the "penetration depth," can provide information about the stand density. Interestingly, the penetration depth ΔE can be derived from the time offset ΔT V . Using the control arrangement 6, a value for the stand density is determined based on a temporal relationship within the resulting echo pulse 11. The above-mentioned temporal relationship is the above-mentioned time offset ΔT V between two partial echo pulses 11a, 11b, here between the first partial echo pulse 11a and the last partial echo pulse 11b, which are assigned to a transmission pulse 8.

[0035] Fig. 3b) shows that the time offset ΔT V can be derived to a certain extent from the resulting echo pulse 11. Preferably, the time offset ΔT V is determined from a pulse width 15 of the resulting echo pulse 11, wherein the pulse width 15 is defined by the time interval between the first rising pulse edge 16 and the last falling pulse edge 17 of the resulting echo pulse 11.

[0036] Furthermore, it is provided that the time offset ΔT V is determined by subtracting a normalization width 18 from the pulse width 15, wherein the normalization width 18 is preferably defined by a pulse width 15a of the resulting echo pulse 11a, which would result from an assumed single reflection of the transmitted beam 9 on a plant 3a of the field 2. In the illustrated embodiment, the normalization width 18 is therefore the pulse width 15a of the first partial echo pulse 11a. For the sake of simplicity, it is assumed that the pulse widths 15a, 15b of the two partial echo pulses 11a, 11b are identical to one another.

[0037] As mentioned above, the value for the stand density can generally be determined from the penetration depth ΔE. Preferably, the value for the stand density is determined by calculating the inverse of the penetration depth ΔE of the transmitted beam 9 into the field stand 2 and by determining the penetration depth ΔE from the product of the time offset ΔT V and the propagation velocity and, if necessary, by a normalization factor. This inverse is then multiplied by a proportionality factor to obtain the desired value for the stand density, depending on the definition of the stand density.

[0038] Various advantageous variants are conceivable for the design of the sensor arrangement 7. Here, and preferably, the electromagnetic beams are optical beams, in particular laser beams, whose transmission direction 10 can be adjusted by means of the control unit 6. In a particularly preferred embodiment, the sensor arrangement 7 is a laser scanner 7a that scans the field 2 or the area 25 in horizontally aligned lines. For this purpose, the inclination angle α of the transmission beam 9 about the horizontal and the scanning angle β about the vertical can be adjusted by means of the control arrangement 6.

[0039] Preferably, the sensor arrangement 7 is configured as an optical distance sensor, wherein the sensor arrangement 7 determines a distance value 22 between the sensor arrangement 7 and the respective reflecting plant 3a from the time interval Ts between the transmission time of a transmission pulse 8 and the reception time TE of the associated echo pulse 11. As mentioned above, the sensor arrangement 7 is preferably a time-of-flight sensor arrangement.

[0040] In the sensor arrangement 7 designed as a laser scanner 7a, it is preferably the case that the transmission direction 10 of the sensor arrangement 7 is continuously modified in the horizontal direction and / or in the vertical direction by means of the control unit 6. In a particularly preferred embodiment, it is provided that a stand height 23 is determined by means of the control unit 6 from the distance values ​​and / or the values ​​for the stand density. In the case of the laser scanner 7a mentioned above, a line-by-line scanning of the field stand 2 is provided, with the angle of inclination α being selected to be increasingly flatter. Upon reaching the upper ridge line of the field stand 2, not only the distance values ​​mentioned above but also the values ​​for the stand density change abruptly, from which the position of the ridge line and thus the stand height 23 can be recorded automatically.

[0041] Alternatively or additionally, it may be provided that the position of a lateral crop edge 24 is determined from the distance values ​​22 and / or the crop density values ​​by means of the control unit 6. This can also be accomplished by automatically detecting a sudden change in the relevant values.

[0042] Alternatively or additionally, it is further provided that the control unit 6 determines the position of an obstacle from the distance values ​​and / or the values ​​for the stand density. This determination can also be traced back to the automated detection of a sudden change in the relevant values.

[0043] As already explained above, in addition to the plants 3 of the field 2, the soil 4 on which the field 2 is located forms a reflection surface RF for the respective transmission beam 9. The generalized representation in Fig. 4 a)shows two separate partial echo pulses E1, E2 and Fig. 4 b) shows two superimposed partial echo pulses E1, E2. The partial echo pulse E1 results from the reflection of the transmitted beam 9 from one of the plants 3, and the partial echo pulse E2 results from the reflection of the transmitted beam 9 from the ground 4. The resulting echo pulse 11 is composed of the partial echo pulses E1 and E2.

[0044] In the Fig. 4 a) and 4 b) 26 denotes a first rising edge of the reflected partial echo pulse E1, and 27 denotes a last falling edge of the reflected partial echo pulse E2. The first rising edge 26 of the partial echo pulse E1 marks the impact of the transmitted beam 9 on the plants 3 of the field stand 2, and the last falling edge 27 of the partial echo pulse E2 marks the corresponding ground level.

[0045] Based on a time offset ΔT F between the first rising edge 26 and the last falling edge 27 of one or more emitted electromagnetic transmission pulses 8 for an accumulation of measured values ​​in a limited segment within a plant stand 2 and sensor-specific characteristic values, statements can be made about the extent of the plant stand 2 or the stand height 23 and the position of the ground level. This will be explained below using the Fig. 5 a), 5 b) and 6 a), 6 b) further illustrated.

[0046] In Fig. 5 a) is an example of a cross section of height values ​​of a field 2a of a maize field and in Fig. 5 b) An example of an echo pulse shape 28 of a field reflection of maize plants and a soil reflection of the soil 4 is shown as the respective reflection surface RF. In Fig. 5 a)only the position of the laser scanner 7a arranged on the working machine 1 is indicated and only one emitted transmission beam 9 is shown as an example, which first hits the field 2a consisting of the maize plants and then the ground 4 and is partially reflected with a time delay in each case.

[0047] The resulting echo pulse curves 30, 31 in the case of maize plants as field crop 2a, where the echo pulse curve 30 corresponds to the field crop reflection of the maize plants and the echo pulse curve 31 corresponds to the ground reflection, are shown as an example in Fig. 5 b) Due to the shorter distance between the ridge line of the field crop 2a and the laser scanner 7a mounted on the working machine 1 compared to other crop types, the partial echo pulses E1 of the maize plants are detected first, followed by the partial echo pulses E2 of the ground reflection, with a significant time offset due to the crop height 23.

[0048] A first distance 32 between the laser scanner 7a and the ridge line of the field 2a is the distance to be covered by the transmitted pulse 8 and the reflected partial echo pulse E1, and a second distance 33 between the ridge line and the field soil 4 is the additional distance that the transmitted pulse 8 and the partial echo pulse E2 reflected from the soil 4 have to cover. The resulting time interval between the partial echo pulses E1, E2 enables a clear distinction between the field 2a and the soil 4, on the one hand, and, based on the pulse shape 28, an identification of the crop type of the plants within the field 2a, here the maize plants, using at least one reference curve specific to the maize crop type. Fig. 5b) the first rising flank 26 and the last falling flank 27 are identified as examples, from whose time offset ΔT F statements are made about the extent of the plant stand 2a or the stand height 23 and the position of the ground level.

[0049] In Fig. 6 a) is an example of a cross section of height values ​​of a field 2b of a rapeseed field and in Fig. 6 b) An example of an echo pulse shape 29 of a field reflection of rapeseed plants and a ground reflection is shown. As in Fig. 5 a) also, is in Fig. 6 a) only the position of the laser scanner 7a arranged on the working machine 1 is indicated and only one emitted transmission beam 9 is shown as an example, which first hits the field stand 2b consisting of the rapeseed plants and then the ground 4 and is partially reflected with a time delay in each case.

[0050] The field stand 2b consisting of rapeseed plants has a lower stand height 23 than the field stand 2a consisting of maize plants, so that the difference between the first distance 32 and the second distance 33 and the associated signal propagation times is considerably smaller in relation to the field stand 2a consisting of maize plants. Accordingly, the field stand 2b consisting of rapeseed plants exhibits a different echo pulse shape 29 than the field stand 2a consisting of maize plants. Fig. 6b ) the first rising flank 26 and the last falling flank 27 are identified as examples, from whose time offset ΔT F statements are made about the extent of the plant stand 2b or the stand height 23 and the position of the ground level.

[0051] Different digital image processing methods can be used to evaluate projected sensor data from laser scanner 7a. Accordingly, control unit 6 can also be configured for image processing and image evaluation.

[0052] The laser scanner 7a can be implemented as a solid-state LiDAR, a Geiger-mode LiDAR, a scanning LiDAR, or a single-photon LiDAR. Different information contained in the LiDAR sensor signals is used for evaluation and classification. For example, a point cloud generated by the laser scanner 7a can be evaluated to classify geometric environmental and object properties. The evaluation of the amplitude or intensity of the resulting echo pulse 30, 31 can enable the determination of the surface color and / or surface roughness of the reflection surfaces RF. The detection of surface and / or object and / or environmental structures can be influenced by ambient light.Thus, the influence of ambient light can be taken into account when evaluating the LiDAR sensor signals in order to avoid distortions when classifying the surface and / or object and / or surrounding structures of the reflection surfaces RF. The evaluation of the temporal signal shape or waveform of the pulse shapes 28 can be used to determine the surface and / or internal object structure. The evaluation of the wavelength of the transmitted transmission pulse 8 can be used to determine a surface color and / or surface roughness and / or a composition of the reflection surfaces RF. The various information contained in the LiDAR sensor signals listed above can be partially evaluated with the same goal, e.g., determining the surface structure, surface color, or surface roughness.

[0053] According to a preferred development, at least one additional optical sensor arrangement, different from a laser scanner 7a, can be used to classify the reflection surface RF as well as the crop type and / or the foreign vegetation. Incorporating an additional optical sensor arrangement that is not designed as a laser scanner can contribute to improving the analysis process during classification. For example, a camera can be provided as an additional optical sensor arrangement that generates images in the visible spectral range. Alternatively, a camera can be provided as an additional optical sensor arrangement that generates images in the near-infrared range.By incorporating RGB camera images or infrared camera images as well as additional specific features of the reflecting surface RF as well as the vegetation and / or foreign growth, such as shape, color, structure, and the like, the classification result can be improved. List of reference symbols 1 Work machine 23 Stock level 2 Field inventory 24 Existing edge 2a Corn field crop 25 Area 2b Rapeseed field 26 First rising flank 3 plant 27 Last sloping flank 3a Front plant 28 Echo pulse shape 3b Rear plant 29 Echo pulse shape 4 field soil 30 Echo pulse curve 5 Direction of travel 31 Echo pulse curve 6 Control unit 32 First distance 7 Sensor arrangement 33 Second distance 7a Laser scanner M Measuring spot front 8 Transmission pulse M' Rear measuring spot 9 Transmission beam 10 Transmission direction 11 Echo pulse 11a Partial echo pulse 11b Partial echo pulse 12 Partial beam 13 Partial beam 14 ear of corn 14a Front ear 14b Rear ear 15 Pulse width 15a Pulse width 15b Pulse width 16 Pulse edge 17 Last falling pulse edge 18 Standardization width 19 Width 20 diameter 21 Excluded area 22 Distance value

Claims

1. A method for detecting the ground level on an area (25) to be processed by an agricultural working machine (1), wherein the working machine (1) comprises a sensor system (7) by means of which periodic transmitted pulses (8) produced from electromagnetic transmitting beams (9) are emitted in at least one transmitting direction (10) onto the area (25) to be processed, wherein the transmitted pulses (8) are reflected from a field crop (2, 2a, 2b) and ground (4) as reflecting surfaces (RF) and are received by the sensor system (7) as echo pulses (11) and transferred to a control unit (6) of the working machine (1) for analysis, wherein, for at least a portion of the transmitted pulses (8) emitted by the sensor system (7) which is configured as a laser scanner (33), different partial beams (12, 13) of one and the same transmitting beam (9) are reflected with a time delay with respect to one another from reflecting surfaces (RF) located in the respective transmitting direction (10), so that the respective resultant echo pulse (11) is composed of correspondingly time-delayed partial echo pulses (11a, 11b, E1, E2), wherein the ground level and / or a crop height (23) is determined by means of the control unit (6) on the basis of a pulse width (ΔTF) within the resultant echo pulse (11) and / or on the basis of a pulse form (28, 29) of the resultant echo pulse (11) as well as a time of flight-based distance determination of a distance value (32, 33) to the respective reflecting surface (RF).

2. The method according to claim 1, characterized in that plants of different crop types are distinguished by processing and analysing the signal form with respect to time of the echo pulses which are provided by the sensor system (7) which is configured as a laser scanner (7a).

3. The method according to claim 2, characterized in that a distinction between different crop types of the field crop (2, 2a, 2b) is made with the aid of a measure of the dispersion of the reflection height and / or of the signature of the pulse form (28, 29) by means of a comparison with reference curves.

4. The method according to claim 3, characterized in that a variance, a standard deviation or a quantile is used as the measure of the dispersion.

5. The method according to claim 3 or claim 4, characterized in that the distinction between different crop types of the field crop (2, 2a, 2b) is made with the aid of the pulse width (15) related to a predetermined threshold value for an accumulation of measured values in a spatially delimited segment within the field crop (2, 2a, 2b).

6. The method according to one of the preceding claims, characterized in that impingement on the field crop (2, 2a, 2b) is determined with the aid of a first ascending flank (26) of the respective resultant echo pulse (11) and impingement on the ground (4) is determined with the aid of a last descending flank (27) of the resultant echo pulse (11).

7. The method according to claim 6, characterized in that the crop height (23) and the position of the ground level are determined with the aid of a time delay (ΔTV) between the first ascending flank (26) and the last descending flank (27) of the respective resultant echo pulse (11) for an accumulation of measured values in a segment within the field crop (2, 2a, 2b).

8. The method according to one of the preceding claims, characterized in that at least one handling instruction for influencing the operation of the working machine (1) is generated by the control unit (6) on the basis of the detection of at least the ground level.

9. The method according to claim 8, characterized in that a specification and / or a selection of initial operating parameters for at least one working assembly of the agricultural working machine (1) is made as the at least one handling instruction.

10. The method according to one of the preceding claims, characterized in that the reflective intensity of the respective echo pulse (11), the wavelength and / or ambient lighting conditions are determined by the laser scanner (7a).

11. The method according to one of the preceding claims, characterized in that at least one additional optical sensor system which is different from a laser scanner (7a) is used for the classification of the crop type and / or of extraneous vegetation.

12. The method according to one of the preceding claims, characterized in that statistical or adaptive threshold value methods or non-analytical methods are used for the analysis of the respective resultant echo pulse (11).

13. An agricultural working machine (1), in particular a self-propelled harvesting machine or a tractor, which is equipped with the technical means for carrying out a method according to one of the preceding claims.

14. The agricultural working machine (1) according to claim 13, characterized in that the laser scanner (7a) is configured as a solid state lidar, a Geiger mode lidar, a scanning lidar or a single photon lidar.