BACKGROUND TO INVENTION Forest harvesting involves cutting down standing trees to obtain felled stems and then cutting these stems into logs. A stem is typically of variable quality with the most valuable wood at the stump end of the stem and the less valuable wood nearer the top. Stem characteristics such as the quality of the stem are also affected by the stem diameter, the placement and size of the branches and/or the extent of curvature in the stem, known as sweep.

It has become particularly important to develop a method for determining where to make the cuts on a stem to optimize the value of the logs that result. Logs can be cut into a variety of lengths and diameter range, known as the log grade, to meet market demands.

Each grade may have a different value depending on market demand. Optimizing value involves capturing the characteristics of a stem in some fashion, processing that information having regard to the log grade and market price, and determining where to cut the stem into logs for maximum financial return.

It has also become particularly important to develop a method of being able to trace logs back to the stems from which they are cut.

One method of capturing the characteristics of a stem for the purposes of optimizing the process of log-making is for a person experienced in the business of cutting stems into logs

to make a value judgement. An experienced forestry worker uses a tape measure and callipers to determine log lengths and diameters and then marks the stem at the appropriate position so that a saw operator may saw the stem into lengths at the appropriate positions.

New Zealand patent specification 245399 to Interpine Export (NZ) Limited entitled "Portable Apparatus for Determining Cut Positions in Logs"describes a pair of hand-held callipers for measuring diameters at positions along the stem and a tape measure for measuring distance along the stem. The tool includes a programmed processor which is pre-programmed with information relating to log grade requirements and prices and determines the optimal cutting positions along the stem to maximise the value of logs from the stem. Once the optimal positions have been determined, the operator marks a paint mark at the points where the stem is to be cut.

It would be particularly desirable to measure the characteristics of felled stems in a much more accurate manner. It would also be desirable to at least partially automate the step of cutting the logs from the stem based on the stem characteristics.

SUMMARY OF INVENTION In broad terms in one form, the invention comprises a method of cutting logs from a stem comprising the steps of measuring characteristics of a stem; determining the preferred cut location or locations on the stem from the stem characteristics; directing a cutting tool to the preferred cut location (s); and cutting the stem at the preferred cut location (s) to form one or more logs.

In broad terms in another form the invention comprises a method of determining one or more cut locations on a stem comprising the steps of calculating a plurality of spatial co- ordinates defining the surface of at least part of the stem; storing the spatial co-ordinates in a memory; and determining the preferred cut location (s) on the stem from the spatial co- ordinates stored in the memory.

BRIEF DESCRIPTION OF THE FIGURES Preferred forms of the method of cutting logs from a stem and the method of determining one or more cut locations on a stem will now be described with reference to the accompanying figures in which: Figure 1 is a flow chart of a preferred form method of assessing the optimal positions on a stem for cutting that stem into logs in accordance with the invention; Figure 2 is a preferred form harvest worksite layout in accordance with the invention; Figure 3 is a preferred form stem attribute recorder; Figure 4 is a further view of the preferred form stem attribute recorder of Figure 3; Figure 5 shows one preferred form stem attribute recorder mounted on an excavator; Figure 6 shows a set of spatial co-ordinates captured by the stem attribute recorder of Figures 2 to 4; Figure 7 shows a further set of spatial co-ordinates captured by the stem attribute recorder ; Figure 8 shows an enhanced representation of the spatial co-ordinates of Figure 7; Figure 9 shows a preferred form user interface of log optimizing software; and Figure 10 shows the cutting tool mounted on the excavator of Figures 2 and 5 in operation.

DETAILED DESCRIPTION OF PREFERRED FORMS Figure 1 illustrates one application of the invention in assessing the optimal positions on a stem for cutting that stem into logs. As indicated at 10, the stem characteristics of each stem are captured and stored by a stem attribute recorder which is further described below.

In one form the stem attribute recorder includes a laser emitter and laser beams are directed towards the stem from this laser emitter. From the reflected laser signals the stem attribute recorder obtains a plurality of spatial co-ordinates defining the surface of at least part of the stem. These spatial co-ordinates preferably comprise a series of (x, y, z) co-ordinates. The stem attribute recorder stores these spatial co-ordinates in a memory, for example a computer memory interfaced to a computing device. A 3-dimensional surface model can then be obtained from these co-ordinates.

As shown at step 20, these stem characteristics are then pre-processed to derive a desired set of stem dimensions. These stem dimensions could include, for example, detailed measurements for stem diameter at any point of the stem, branch position and size, stem length measurement to determine the various sections for each grade of wood quality, wood volume calculations and/or stem straightness. Examples of these pre-processing calculations are described below.

As shown at step 30, it is then necessary to determine the optimal cut location or locations from the stem characteristics. Existing systems which could be used include Timbertech which is based on log grade optimizing models. The stem characteristics captured by the stem attribute recorder in step 10, following processing in step 20, are passed to one of the existing log optimizer models to calculate the optimal positions along a stem where saw cuts are to be made during the production of logs. It is envisaged that the pre-processing performed in step 20 calculates parameters needed by the log optimizer system, for example stem diameters, placement and size of branches, internode length, and sweep.

Referring to step 40, a cutting tool is preferably arranged to pick up an individual stem, remove branches from the stem and cut the stem into logs. The preferred cutting tool is interfaced to the log optimizer so that the cutting tool can be directed to the cut location (s) based on the stem characteristics calculated from the spatial co-ordinates, and the optimal cut location (s) calculated above. Preferably the step of directing the cutting tool is at least partially automated in that the cutting tool can be programmed to be positioned at different locations along the stem.

Referring to step 50, the stem is then cut into logs at the appropriate positions. Each log is then tagged as shown at 60 to enable the log to be traced back to the stem from which it is cut as will be described below.

Referring to step 70, if there are further stems to process then the stem attribute recorder is used to capture the stem characteristics of those further stems.

Figure 2 shows one preferred form of the invention arranged in a harvest work site 100. A stem attribute recorder 110 in one form could be a free standing device mounted on a suitable bracket or other mounting structure.

A full length stem from a stack 130 of such stems is positioned in a cradle 140. The stem attribute recorder 110 is positioned close to the stem 120 supported in the cradle. The recorder 110 is preferably a 3-dimensional laser distance measurement device arranged to direct laser beams toward the stem 120 and to record the laser beams reflected from the surface of the stem.

The recorder 110 could be arranged to direct laser beams to consecutive locations along the stem surface. From the reflected laser beams, the stem attribute recorder 110 captures a series of spatial (x, y, z) co-ordinates defining the surface of at least part of the stem.

An excavator 150 is preferably fitted with a cutting tool or processing head 160, such as a Waratah processing head. The processing head 160 is arranged to pick up individual stems from the stack of stems 130 and to cut the stems into logs and stack these logs as shown at 170. The stem attribute recorder 110 is preferably arranged to obtain raw scan stem images and to extract and store in a memory a series of spatial co-ordinates from the stem images in order to direct the processing head 160 to the preferred cut location or locations on the stem 120 as will be described below.

Referring to Figure 3, the preferred form stem attribute recorder 110 includes a housing 180 mounted on a base 190 including one or more adjustable mounts 200. The recorder 110 is preferably arranged to be removed at night and replaced daily in one or more preset level positions.

As shown in Figure 4, the stem attribute recorder 110 includes a Perspex dome 210 through which laser beams are directed. The recorder 110 also includes a combination computing device and display unit 220 interfaced to a computer memory.

In use, the stem attribute recorder 110 is controlled by the operator in the excavator 150 by way of a wireless network link. Once the operator has placed a stem in the cradle in front of the stem attribute recorder, the recorder is activated and the scanner sweeps the surface of the stem for a duration of approximately 45 seconds. Once the scan is complete, the resulting data is stored in the memory of the computing device 220 and then transmitted to a computing device with memory on the excavator 150 where a 3-dimensional model of the stem is created as will be described below. The model is then processed by log optimizing software installed and operating on the memory of the computing device to optimize the cutting of the stem into logs. The cut positions are displayed to the excavator operator who can override any suggested cut position. The model is then re-optimized and the cut positions relayed to a processing head controller.

Figure 5 shows another preferred form stem attribute recorder 110A. The recorder 110A is mounted on the excavator 150 as opposed to being free-standing. The recorder 110A could alternatively be mounted elsewhere on the excavator 150 or alternatively could be mounted on any other machine or apparatus. The recorder 110A is positioned close to the stem 120.

Laser beams are directed toward the stem 120, and the laser beams reflected from the surface of the stem 120 are recorded.

Figure 6 indicates at 300 the spatial co-ordinates of a stem captured by the attribute recorder. The invention is then arranged to calculate from these spatial co-ordinates a series of measurements to pass to log optimizer software.

Measurements required by the software generally include stem diameter at various points along a stem and include sweep. The spatial co-ordinates at position 310, for example, will define an arc representing the surface of the stem at point 310 which is visible to the stem attribute recorder. A series of arcs can be obtained in this manner for points 320,330 and 340. The circumference of the stem at points 310,320,330 and 340 can then be obtained from the arcs and represented for example at 350. It is envisaged that stem diameter can also be obtained from these series of arcs.

Each of the diameter representations shown at 350 will have a centroid represented by a spatial co-ordinate which in practice represents the centre of the stem at one of the capture points. By comparing the spatial positions of the centroids of each diameter representation 350, the system is able to assess the degree of curvature or sweep in the tree stem.

The size and positioning of the branches can also be obtained from the spatial co-ordinate model of the stem to provide an indication of, for example, internode lengths of tree stems.

Figure 7 shows a graphical representation of the spatial co-ordinates of a stem captured by the stem attribute recorder. As shown in Figure 8, the intensity or colour of the image could be varied so that points on a stem closest to the stem attribute recorder could be

shown in one colour or shade, for example red, and points on the stem further from the stem attribute recorder could be shown in blue or black.

The above measurements can then be passed to log optimising software to determine the optimal cut location or cut locations from the stem characteristics. The log optimizer software could be installed in a computing device interfaced to or accessible by the stem attribute recorder 200. The computing device is preferably mounted on the excavator and accessible to the operator.

Figure 9 shows a preferred form user interface for log optimizer software presented to an operator of the excavator. The panel 400 presented to an operator could be further divided into a log image panel 410, a data panel 420, and/or an options panel 430.

The image panel 410 presents to a user an image 440 of a log. The image 440 is divided into a series of sections, for example 450,460 and 470, each of the sections representing a preferred log to cut from the stem, each section defined by one or more optimal cut locations.

The data panel 420 could present data to a user representing the optimal cut location. For example, log 460 is represented by cut positions shown at 480 and 490.

An options panel 430 enables the user to change the layout or scale factors of the log image in the image panel or change the appearance of data represented in the image panel. The user could also be provided with a manual override in which the user may select a desired cut position different to that suggested by the log optimizing software. Once the user selects a manual override, the user could then direct the software to optimize or recalculate the preferred cut positions.

The log optimizing software preferably includes a pointing device, for example a touch sensitive screen, mouse, or stylus to manually position optimal cut locations and to select options in the options panel 430.

Referring to Figure 10, the cutting tool or processing head 160 mounted on the excavator 150 is preferably operable by a processing head controller in that the cutting tool can be directed automatically to various positions on the stem 130 based on instructions from the processor. Preferably, the stem attribute recorder and log optimising software are interfaced to the cutting tool 160 so that the cutting tool can be directed to the preferred cut locations calculated by the log optimising software.

In one preferred form, the stem attribute recorder captures a digital image and stores this digital image together with the spatial co-ordinates for individual stems in a memory. In this way, it is possible to store the stem characteristics in a database together with data representing each log section generated from each stem. Unique identifiers or tags can then be generated and attached to each log and the associated identifier or tag number stored in the stem attribute database. In this way, it is possible to trace logs back to the stems from which they were cut.

Using the method described above, calculation of optimized log cut positions on a stem, and provision of information to a machine mounted processing head as to where to make. cuts to a stem, enables forestry companies to make highly accurate decisions with regard to maximising the value of logs produced from stems.

The foregoing describes the invention including preferred forms thereof. Alterations and modifications as will be obvious to those skilled in the art are intended to be incorporated within the scope hereof, as defined by the accompanying claims.