Patent Description:
An agricultural harvester, such as, but not limited to, a combine or a windrower, generally includes a header operable for severing and collecting plant or crop material as the harvester is driven over a crop field. In order to minimize harvesting time, the width of the header has been increased over the years to harvest more crop during each pass of the harvester.

As the widths of the headers have increased, articulated headers (headers with more than one segment) have been developed to more closely follow the contours of the field. Additionally, outward segments of these articulated headers may be raised to avoid flooded areas of a field that could bog down the header. The height of the header (or portions thereof) above ground may be monitored using feeler arms. <CIT> describes a combine including a harvesting head position control system with position transducers along the harvesting head and a comparison circuit, which selects the signal produced by the sensor associated with the smallest distance between the head and ground. <CIT> describes a combine with an array of ground engaging skid shoes divided into right- and left-hand groups, each group associated with a position sensor switch.

A harvesting apparatus according to claim <NUM>.

A method for controlling the height of a header for use with an agricultural harvester according to claim <NUM>.

For the purpose of illustration, there are shown in the drawings some examples of the invention. When more than one of the same or similar elements are depicted a common reference number may be used with a letter designation corresponding to respective elements. When the elements are referred to collectively or a non-specific element is referenced, the letter designation may be omitted. In the drawings:.

Reference will now be made in detail to the various examples of the subject disclosure illustrated in the accompanying drawings. According to examples described herein, header height above ground is detected at multiple locations across the width of the header (e.g., at each float arm). Header heights from adjacent locations are combined, with the lowest header height selected as the height for use in controlling the height of the header. This guards against the use of uncharacteristic values that may be detected, e.g., by a feeler arm that is in a tire rut.

Certain terminology is used in the following description for convenience only and is not limiting. Directional terms such as top, bottom, left, right, above, below and diagonal, are used with respect to the accompanying drawings. The term "distal" shall mean away from the center of a body. The term "proximal" shall mean closer towards the center of a body and/or away from the "distal" end. The words "inwardly" and "outwardly" refer to directions toward and away from, respectively, the geometric center of the identified element and designated parts thereof. Such directional terms used in conjunction with the following description of the drawings should not be construed to limit the scope of the subject application in any manner not explicitly set forth. Additionally, the term "a," as used in the specification, means "at least one. " The terminology includes the words above specifically mentioned, derivatives thereof, and words of similar import.

The term "crop material" is used throughout the specification for convenience and it should be understood that this term is not intended to be limiting. The header of the subject application is applicable to a variety of crops, including but not limited to wheat, soybeans and small grains.

The term "coupled" as used herein refers to any logical, optical, physical or electrical connection, link or the like by which signals or light produced or supplied by one system element are imparted to another coupled element. Unless described otherwise, coupled elements or devices are not necessarily directly connected to one another and may be separated by intermediate components, elements or communication media that may modify, manipulate or carry the signals or light.

The term "about" as used herein when referring to a measurable value such as an amount, a temporal duration, and the like, is meant to encompass variations of ±<NUM>%, ±<NUM>%, ±<NUM>%, ±<NUM>%, or ±<NUM>% from the specified value, as such variations are appropriate.

The term "substantially" as used herein shall mean considerable in extent, largely but not wholly that which is specified, or an appropriate variation therefrom as is acceptable within the field of art.

Throughout the subject application, various aspects thereof can be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as a limitation on the scope of the subject disclosure. For example, description of a range such as from <NUM> to <NUM> should be considered to have specifically disclosed subranges such as from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM> etc., as well as individual numbers within that range, for example, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>.

Furthermore, the described features, advantages and characteristics of the examples of the subject disclosure may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize, in light of the description herein, that the subject disclosure can be practiced without one or more of the specific features or advantages of a particular example. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all examples of the present disclosure.

Referring now to the drawings, <FIG> illustrates an agricultural harvester <NUM> for harvesting crop material in accordance with an example of the present disclosure. For exemplary purposes only, the agricultural harvester is illustrated as a combine harvester. The harvester <NUM> includes a header <NUM> attached to a forward end of the harvester, which is configured to cut crops, including (without limitation) small grains (e.g., wheat, soybeans, grain, etc.), and to induct the cut crops into a feeder house <NUM> as the harvester moves forward over a crop field.

The header <NUM> is an articulating header including a center segment 150A, a right wing segment 150B adjacent a right side of the center segment 150A, and a left with segment 150C adjacent a left side of the center segment. The center segment 150A is positioned in front of the feeder house <NUM> and may be raised/lowered with respect to the harvester <NUM>. The right wing segment 150B and the left wing segment 150C may be raised/lowered to conform to the surface of the crop field. During normal operation, all three segments 150A/150B/150C are engaged in harvesting crop material from the crop field (referred to herein as the "operational state"). In certain situations, such as in an unusually wet/muddy portion of the crop field, the right and/or left wing segments 150B are raised such that they no longer effectively capture crop (referred to herein as a "raised state") in order to prevent the header <NUM> from getting bogged down in the crop field.

The header <NUM> includes a frame <NUM> having a floor <NUM> that is supported in desired proximity to the surface of a crop field. The center, right, and left segments 150A, 150B, and 150C extend transversely along a forward edge of the floor <NUM>, i.e., in a widthwise direction of the harvester. The center, right, and left segments 150A, 150B, and 150C are configured to cut crops in preparation for induction into the feeder house <NUM>. The header <NUM> may include one or more draper conveyor belts for conveying cut crops to the feeder house <NUM>, which is configured to convey the cut crops into the harvester for threshing and cleaning as the harvester <NUM> moves forward over a crop field. The header <NUM> may include an elongated, rotatable reel <NUM> which extends above and in close proximity to the segments 150A, 150B, and 150C. The rotatable reel <NUM> is configured to cooperate with the one or more draper conveyors in conveying cut crops to the feeder house <NUM> for threshing and cleaning. According to an example as shown in <FIG>, a cutter bar <NUM> is positioned in front of the segments 150A, 150B, and 150C.

<FIG>, <FIG> depict the header <NUM> with its segments <NUM> in various states of operation. <FIG> depicts the header <NUM> with the center segment 150A and the left segment 150C in an operational state, and the right segment 150B in a non-operational state. <FIG> depicts the header <NUM> with all segments <NUM> in the operational state. <FIG> depicts the header <NUM> with the center segment 150A and the right segment 150B in an operational state, and the left segment 150C in a non-operational state. <FIG> depicts the header <NUM> with the center segment 150A in an operational state, and the left segment 150C and the right segment 150B in non-operational states.

In one example, positioning machinery including a hydraulic control apparatus <NUM> and hydraulic cylinders <NUM>. The hydraulic control apparatus <NUM> (e.g., under control of a microprocessor of the harvester <NUM> or located in the header <NUM>) controls a first hydraulic cylinder 202A positioned between the center segment 150A and the right segment 150B and a second hydraulic cylinder 202A positioned between the center segment 150A and the left segment 150C. The controller <NUM> controls the flow of hydraulic fluid through respective first and second fluid lines 206A and 206B to the first and second hydraulic cylinders 202A and 202B.

Increasing the pressure in the first fluid line 206A causes the hydraulic cylinder 202A to extend, which results in the right wing segment 150B raising with respect to the center segment 150A (and into a non-operational state) as it rotates about a pivot point 204A therebetween. Decreasing the pressure in the first fluid line 206A causes the hydraulic cylinder 202A to retract, which results in the right wing segment 150B lowering with respect to the center segment 150A (and into an operational state). Increasing the pressure in the second fluid line 206B causes the hydraulic cylinder 202B to extend, which results in the left wing segment 150C raising with respect to the center segment 150A (and into a non-operational state) as it rotates about a pivot point 204B therebetween. Decreasing the pressure in the second fluid line 206A causes the hydraulic cylinder 202B to retract, which results in the left wing segment 150C lowering with respect to the center segment 150A (and into an operational state).

<FIG> depict a two-segment header <NUM> with height detectors extending from a bottom portion of the header. In the illustrated embodiment, the height detectors include feeler arms <NUM> (feeler arms 300a-h). As described in further detail below, the feeler arms <NUM> are grouped into feeler arm groups <NUM> (feeler arm groups 302a-d), with each feeler arm group <NUM> including a pair of feeler arms. Although each group <NUM> is illustrated and described as including a pair of feeler arms <NUM>, a group <NUM> may include more than two feeler arms <NUM>.

<FIG> depict a three-segment header <NUM> with height detectors <NUM> (height detectors 310a-l) extending from a bottom portion of the header. In the illustrated embodiment, the height detectors <NUM> may be feeler arms <NUM> such as described above with respect to <FIG> or may be another type of height sensor such as a laser distance sensor. Some of the height detectors <NUM> (e.g., height detectors 310a-l) are grouped into height detector groups <NUM> (height detector groups 312a-f), with each height detector group <NUM> including a pair of height detectors <NUM>, and other height detectors (e.g., height detectors <NUM> and <NUM>) may stand alone. Although each group <NUM> is illustrated and described as including a pair of height detectors <NUM>, a group <NUM> may include more than two height detectors <NUM>.

The height detectors <NUM> are spaced across the width of the header <NUM>. In the illustrated embodiment, each height detector <NUM> is positioned adjacent a respective float arm (see float arm <NUM>; <FIG>) of the header. Combining the detected heights from adjacent float arm positions and selecting a representative height value (e.g., the smallest) for controlling the header prevents unwanted changes in header height due to abnormalities in the ground surface (e.g., lowering the header <NUM> when a height sensor is in a tire rut). Additionally, finer granularity of height measurement across the header <NUM> can be obtained and processed without increasing the number of inputs to a processor.

<FIG> depicts a float arm <NUM> with a height detector embodied as a feeler arm <NUM> for "above-ground" cutting. The float arm <NUM> is coupled to a support structure <NUM> of the header <NUM>. The float arm <NUM> rotates about a pivot point <NUM> on the support structure <NUM> to enable the front of the header <NUM> to "float" over the crop field. A hydraulic cylinder <NUM> is coupled to the float arm <NUM> on one side of the pivot point <NUM> and a cutter bar <NUM> is coupled to the float arm <NUM> on the other side of the pivot point <NUM>. Pressure to the hydraulic cylinder <NUM> is controlled to raise/lower the float arm <NUM> (and, in turn, the cutter bar <NUM>), e.g., in order to maintain the cutter bar <NUM> at a set height above the ground of the crop field.

<FIG> depicts the feeler arm <NUM> from a rear point of view. The feeler arm <NUM> may be formed using a flexible polymer. This allows the feeler arm <NUM> to flex, which absorbs shock as the feeler arm <NUM> is dragged over the ground (thereby extending its useful life). A coupler <NUM> couples the feeler arm <NUM> to a bushing at a pivot point <NUM> on the float arm <NUM>, e.g., near the cutter bar <NUM>. The coupler <NUM> enables the feeler arm <NUM> to rotate about a pivot axis <NUM> extending through the pivot point <NUM>. A down pressure spring <NUM> urges the feeler arm <NUM> toward the ground and a reverse spring trip <NUM> allows the feeler arm <NUM> to flip forward in the event the harvester is moved in reverse.

<FIG> depicts the feeler arm <NUM> from a side view. A rotation sensor <NUM> (e.g., a proximity sensor such as a Hall effect sensor) is positioned adjacent the pivot point <NUM> to sense rotation of the feeler arm <NUM> about the pivot axis <NUM>. Where the rotation sensor <NUM> is a Hall effect sensor, a magnetic field is used to sense rotational angles (which correspond to the distance the portion of the header to which the feeler arm is attached is above ground) without the need for additional moving parts. A forward edge <NUM> of the feeler arm <NUM> is curved, which moves the sensing point of the feeler arm <NUM> forward as the feeler arm nears the ground.

<FIG> depicts a float arm <NUM> with a height detector embodied as a rotational sensor (not shown) adjacent the pivot point <NUM> of the float arm <NUM> for "on-the-ground" cutting. The float arm <NUM> is coupled to a support structure <NUM> of the header <NUM>. The float arm <NUM> rotates about a pivot point <NUM> on the support structure <NUM> and includes a skid plate <NUM> to enable the front of the header <NUM> to move along the surface of the crop field at ground level. A hydraulic cylinder <NUM> is coupled to the float arm <NUM> on one side of the pivot point <NUM> and a cutter bar <NUM> is coupled to the float arm <NUM> on the other side of the pivot point <NUM>. Pressure to the hydraulic cylinder <NUM> is controlled to raise/lower the float arm <NUM> (and, in turn, the cutter bar <NUM>), e.g., in order to maintain the cutter bar <NUM> at the crop field ground level.

<FIG> depicts a selector circuit overview for receiving multiple height values and selecting/passing a representative height value (e.g., the smallest) from the received height values. The illustrated selector circuit includes a comparator <NUM> and a selector <NUM>. The selector <NUM> includes an inductor coil <NUM> and a switch <NUM>. In <FIG>, the switch <NUM> of the selector is positioned to pass the voltage value V2 (e.g., the voltage from a second height sensor). If a voltage value V1 (e.g., voltage from a first height sensor adjacent the second height sensor) is less than V2, the output of the comparator <NUM> is equal to ground (GND). In this configuration, the inductor coil <NUM> is not energized and the switch remains positioned to pass the voltage value V2. On the other hand, if the voltage value V1 is greater than V2, the output of the comparator <NUM> is equal to five volts (5v). In this configuration, the inductor coil <NUM> is energized and the switch is moved to pass the voltage value V1.

<FIG> depicts a selector circuit implemented using integrated circuitry for receiving multiple height values and selecting/passing a representative height value (e.g., the smallest) from the received height values. The illustrated selector circuit includes an integrated circuit comparator <NUM> (such as a TL712CP C DIFF COMPARATOR <NUM>-DIP available from Texas Instruments of Dallas, TX, USA) and an integrated circuit switch <NUM> (such as a MAX325 Analog Switch available from Maxim Integrated of San Jose, CA, USA).

The comparator <NUM> includes a positive input pin (PIN <NUM>) coupled to V1 and inverting input pin (PIN <NUM>) coupled to V2. The comparator <NUM> additionally includes a power pin (PIN <NUM>) coupled to a power source (PWR), a ground pin (PIN <NUM>) coupled to ground (GND), and an output pin (PIN <NUM>) responsive to the V1 and V2 values. The switch <NUM> includes a normally open pin (PIN <NUM>) connected to V1 and a normally closed pin (PIN <NUM>) connected to V2. The switch <NUM> additionally includes a positive voltage pin (PIN <NUM>) coupled to a power source (PWR), a negative voltage pin (PIN <NUM>) coupled to ground (GND), a first output pin (PIN <NUM>), and a second output pin (PIN <NUM>). The first and second output pins of the switch <NUM> are tied together to provide an output voltage (V) for use as a representative value for determining height of the header adjacent the sensors producing V1 and V2. A first input pin (PIN <NUM>) of switch <NUM> actuates a normally open switch within the switch <NUM> (coupling/uncoupling V1 to the output V) and a second input pin (PIN <NUM>) of switch <NUM> actuates a normally closed switch within the switch <NUM> (uncoupling/coupling V2 to the output V).

If V2 is less than V1, the comparator <NUM> produces a low value at the output pin of the comparator, which is presented to the first and second input pins of the switch <NUM> (leaving the normally open switch open and the normally closed switch closed). This configuration results in V2 being presented as the output voltage V. If V1 is less than V2, the comparator <NUM> produces a high value at the output pin of the comparator, which is presented to the first and second input pins of the switch <NUM> (closing the normally open switch and opening the normally closed switch). This configuration results in V1 being presented as the output voltage V.

<FIG> depicts a flow chart <NUM> of example steps for selecting height information from a pair of height sensors for use in determining the height of a portion of a header above ground. The steps may be performed by a processor (e.g., microprocessor <NUM> and/or <NUM>; <FIG>) executing instruction stored in a memory (e.g., memory <NUM> and/or784), sensors, and/or circuit described herein. The steps are described with reference to hardware described herein, but are not to be limited to such implementations. Although shown as occurring serially, the blocks of <FIG> may be reordered or parallelized depending on the implementation. Additionally, although two sensors are described, it will be apparent that additional groups of two or more sensors may be processes in order to obtain sufficient information across the entire width of the header to accurately maintain header height. Furthermore, one of skill in the art will understand from the description herein that one or more steps/blocks may be omitted and one or more additional/alternative steps may be incorporated.

At block <NUM>, a first height sensor detects a first height value (H1) at a first location on a header and, at block <NUM>, a second height sensor detects a second height value (H1) at a second location on the header. The first and second height sensors may be position adjacent respective float arms <NUM>. The first and second height sensors each may be a feeler arm height sensor such as depicted in <FIG>. The height sensor may be positioned on a float arm such as float arm <NUM> (<FIG>) or at an interface between the float arm <NUM> and a support structure <NUM> for the float arm (<FIG>).

At block <NUM>, a controller receives the first height value and, at block <NUM>, the controller receives the second height value. The controller includes a processor (e.g., microprocessor <NUM> and/or <NUM>; <FIG>) and a selector (e.g., comparator <NUM>/<NUM> and switch <NUM>/<NUM>). The selector may be located on the header <NUM> and the processor may be located in the harvester <NUM> and/or at a remote location.

At block <NUM>, the selector compares the first and second height values and selects a representative height value (e.g., a height value representing the nearest height above the ground). In the illustrated flow chart, if the first height value (H1) corresponds to a smaller height value than the second height value (H2), processing proceeds at block <NUM> with the first height value (H1) being used in calculations for determining header height. If the second height value (H2) corresponds to a smaller height value than the first height value (H1), processing proceeds at block <NUM> with the second height value (H1) being used in calculations for determining header height. If the height sensors include Hall effect proximity sensors that generate a voltage, the height values H1 and H2 correspond to the voltage values V1 and V2 (<FIG> and <FIG>), respectively. It is to be understood that the selector system may be designed such that larger values correspond to larger distances or such that smaller values correspond to larger distances. Suitable variations in design will be understood by one of skill in the art from the description herein.

At blocks <NUM> and <NUM>, the processor determines height of the header in the vicinity of the header where the sensors are located, using H1 where H1 is less than H2 and using H2 where H2 is less than H1. The processor may determine actual height or an equivalent for adjustment purposes based on, for example, a look-up table stored in memory. Alternatively, the processor may calculate actual height or an equivalent for adjustment purposes using an algorithm retrieved from memory.

At block <NUM>, the processor adjusts the header to maintain the header at a set height responsive to the height values. The processor may raise/lower the entire header, one or both wings of a three-part header, or one or more float arms responsive to the height values from the height sensors on the header.

<FIG> is a schematic diagram of an embodiment of a control system <NUM> that may be utilized to control the harvester <NUM>, control the header <NUM> (including reel height), and/or detect crop field parameters (e.g., height for the header above ground by implementing algorithms such as the algorithm depicted and described with reference to <FIG>). In the illustrated example, the control system <NUM> includes a vehicle control system <NUM> (e.g., mounted on the harvester <NUM>). In the illustrated embodiment, the harvester <NUM> includes a spatial locating device <NUM>, which is mounted to the harvester <NUM> and is configured to determine a position of the harvester <NUM>. The spatial locating device <NUM> may also be configured to determine a heading and/or a speed of the harvester <NUM>, for example. As will be appreciated, the spatial locating device <NUM> may include any suitable system configured to determine the position and/or other characteristics of the harvester <NUM>, such as a global positioning system (GPS) or global navigation satellite system (GNSS), for example.

In the illustrated example, the harvester <NUM> includes a steering control system <NUM> configured to control a direction of movement of the harvester <NUM>, and a speed control system <NUM> configured to control a speed of the harvester <NUM>. The illustrated steering control system includes a wheel angle control system <NUM>, a differential braking system <NUM>, and a torque vectoring system <NUM> that may be used to steer (e.g., adjust the steering angle of) the harvester <NUM>. The illustrated speed control system <NUM> includes an engine output control system <NUM>, a transmission control system <NUM>, and a braking control system <NUM>. In addition, the harvester <NUM> includes an implement control system <NUM> configured to control operation of an implement (e.g., height of the header <NUM> and operational states of the header segments <NUM>) and to determine crop field parameters (such as height of the header above ground) from, for example, height sensors coupled to the header <NUM>. Furthermore, the control system <NUM> includes a controller <NUM> communicatively coupled to the spatial locating device <NUM>, to the steering control system <NUM>, to the speed control system <NUM>, and to the implement control system <NUM>.

In some examples, the controller <NUM> is an electronic controller having electrical circuitry configured to process data from the spatial locating device <NUM>, among other components of the harvester <NUM>. In the illustrated example, the controller <NUM> includes a processor, such as the illustrated microprocessor <NUM>, and a memory device <NUM>. The controller <NUM> may also include one or more storage devices and/or other suitable components. The processor <NUM> may be used to execute software, such as software for calculating a target position, iteratively calculating virtual paths, controlling the harvester <NUM>, and so forth. Moreover, the processor <NUM> may include multiple microprocessors, one or more "general-purpose" microprocessors, one or more special-purpose microprocessors, and/or one or more application specific integrated circuits (ASICS), or some combination thereof. For example, the processor <NUM> may include one or more reduced instruction set (RISC) processors.

The memory device <NUM> may include a volatile memory, such as random access memory (RAM), and/or a nonvolatile memory, such as ROM. The memory device <NUM> may store a variety of information and may be used for various purposes. For example, the memory device <NUM> may store processor-executable instructions (e.g., firmware or software) for the processor <NUM> to execute, such as instructions for controlling the harvester <NUM> (e.g., header height and segment state). The storage device (s) (e.g., a nonvolatile/non-transitory storage medium) may include read-only memory (ROM), flash memory, a hard drive, or any other suitable optical, magnetic, or solid-state storage medium, or a combination thereof. The storage device (s) may store data (e.g., field maps, maps of desired paths, vehicle characteristics, etc.), instructions (e.g., software or firmware for calculating crop field parameters such as header height above ground and any other suitable data.

The implement control system <NUM> is configured to control various parameters of the agricultural implement towed by or integrated within the harvester <NUM>. For example, in certain examples, the implement control system <NUM> may be configured to instruct an implement controller (e.g., via a communication link, such as a CAN bus or ISOBUS) to adjust a penetration depth of at least one ground engaging tool of the agricultural implement, which may reduce the draft load on the harvester <NUM>. Furthermore, the implement control system <NUM> may instruct the implement controller to adjust header height, to transition the agricultural implement between a working position and a transport portion, to adjust a flow rate of product from the agricultural implement, to adjust a position of a header of the agricultural implement (e.g., a harvester, etc.), or to adjust which segments of an articulated header are operational/non-operational, among other operations.

In the illustrated example, the operator interface <NUM> may be communicatively coupled to the controller <NUM>. The operator interface <NUM> is configured to present data from the harvester <NUM> and/or the agricultural implement to an operator (e.g., data associated with operation of the harvester <NUM>, data associated with operation of the agricultural implement, a position of the harvester <NUM>, a speed of the harvester <NUM>, the desired path, the virtual paths, the target position, the current position, etc.) via a display <NUM>. The operator interface <NUM> may also be configured to enable an operator to control certain functions of the harvester <NUM> (e.g., starting and stopping the harvester <NUM>, inputting the desired path, raising lower the header, raising/lowering the reel <NUM> etc.).

It should be appreciated that in certain embodiments, the control system <NUM> may include a base station <NUM> having a base station controller <NUM> located remotely from the harvester <NUM>. For example, in certain embodiments, control functions of the control system may be distributed between the controller <NUM> of the harvester <NUM> and the base station controller <NUM>. In some embodiments, the base station controller <NUM> may perform a substantial portion of the control functions of the control system. For example, in some examples, a first transceiver <NUM> positioned on the harvester <NUM> may output signals indicative of vehicle characteristics (e.g., the speed, maximum turning rate, minimum turning radius, steering angle, roll, pitch, rotational rates, acceleration, reel height, or any combination thereof), the position, and/or the heading of the harvester <NUM> to a second transceiver <NUM> at the base station <NUM>. The base station control <NUM> may have a processor <NUM> and memory device <NUM> having all or some of the features and/or capabilities of the processor <NUM> and the memory device <NUM> discussed above. In some examples, the base station <NUM> may include an operator interface <NUM> having a display <NUM>, which may have all or some of the features and/or capabilities of the operator interface <NUM> and the display <NUM> discussed above.

Claim 1:
A harvesting apparatus including a harvester (<NUM>) and a header (<NUM>) coupled to the harvester (<NUM>), wherein the header (<NUM>) includes a plurality of float arms (<NUM>), the harvesting apparatus comprising:
a first height sensor (300a) configured and positioned to detect a first height value representing height above ground at a first location on the header (<NUM>) and coupled to a first of the plurality of float arms;
a second height sensor (300b) configured and positioned to detect a second height value representing height above ground at a second location on the header (<NUM>) and coupled to a second of the plurality of float arms;
positioning machinery (<NUM>) configured to selectively position at least one aspect of the header (<NUM>) with respect to the harvester (<NUM>);
a controller (<NUM>) coupled to the first height sensor (300a), the second height sensor (300b), and the positioning machinery (<NUM>), characterised in that the controller (<NUM>) is configured to:
receive (<NUM>/<NUM>) the first and second height values;
select (<NUM>/<NUM>) a representative height value from the first and the second height values; and
control (<NUM>) the positioning machinery (<NUM>) to position the header (<NUM>) responsive the selected representative height value.