• 专利附录
  • 专利说明
  • 权利要求
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  • 同族专利
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    • 专利摘要:
    The invention relates to a method and an instrument for measuring the positions and properties of individual trees on test surfaces in the forest by means of radio waves for the needs of the forest inventory. Using the method and instrument, sample area measurements can be automated in area-based inventory. The object of the invention is the first method and instrument by which tree positions can be measured in respect of freely shaped and randomly large test surfaces. The equipment uses at least three radio frequency base stations (112-122) and one or more transmitter-receivers (104), an inertial sensor (106) and a magnetometer (108). Distance measurement is done from base stations based on the pulse duration. A local coordinate system is created based on the distances between the base stations by minimizing the error sum.
    公开号:FI20170172A1
    申请号:FI20170172
    申请日:2017-12-20
    公开日:2019-06-21
    发明作者:Pekka Savolainen
    申请人:Terratec Oy；
    IPC主号:
    专利说明:

    METHOD FOR LOCATION AND MEASUREMENT OF TEST TREE
    The invention relates to a method and a device for measuring the location and properties of individual trees in forest plots for forest inventory purposes. The method and the device can automate test site measurements in an area-based inventory. The invention relates to a first method and apparatus for measuring the position of trees in free-form and arbitrarily large plots. The apparatus utilizes at least three radio frequency base stations, and one or more mobile transceivers, an inertia sensor, and a magnetometer. The distance measurement from the base stations is based on the pulse travel time. A local coordinate system is established for distances between base stations by minimizing the amount of error. The mobile station travels to the trees to be measured, logs the tree species and other information, measures the height of the chest, and records the distances to all base stations within range.
    Description of the Related Art
    Airborne laser scanning (also known as ALS) is a remote sensing technique that is used specifically to measure tree and surface contours. The basic idea behind a laser scanner is very simple: the distance between the target and the laser is measured based on the laser pulse travel time, the scanner sweeps the laser pulses in a direction perpendicular to the flight direction, and once the laser scanner position and position are known accurately, the measured distance can be converted to x-y and z-coordinates. The result is a point cloud. Characteristics of individual trees or clusters of trees can be determined from laser scatter point clouds using existing computational formulas shown e.g. In the patent Fl 112402, tree symbols can also be calculated from a point cloud using regional methods. In this case, a classifier is created between the features calculated from the point cloud and the teaching material, which implements the classification of the whole point cloud. In addition, aerial surveys of tree stands require plot data to teach laser features calculated from point clouds. Currently, plot data is manually measured in the field and tree locations are not determined because it is too laborious. The invention speeds up test measurements by 80% and allows for a fivefold amount of test measurements at the same expense.
    The invention thus relates to the measurement of trees and enables the collection of more accurate and faster plot data for forest inventory purposes. Most of the plots measured in forests are circular plots. In these, the only spatial information is the location of the midpoint and, in the case of trees, whether the tree trunk is within the radius of the circle. Efforts have been made to locate the wood more precisely. One way is to measure the direction and distance of the body from the center. Also, a positioning method based on multiple ultrasonic transponders has been developed to obtain locations in small test areas. Using satellite positioning (GNSS) would be an easy and straightforward solution, but unfortunately there are not enough satellite observations for real-time positioning in a covered forest. Multipath reflections also reduce the accuracy of satellite positioning in a covered terrain. By using a high antenna mast (3-4 m), long measurement time (10-30 min) and as many satellite receivers (GPS, GLONASS, GALILEO, BEIDOU) as possible, it is possible to achieve positioning accuracy of up to 10 cm with static measurement even in forest conditions.
    For example, prior art tree positioning techniques include U.S. Patent 5,953,975 (Machine for Positioning and Cutting Tree Trunks), where wood positioning refers to placing a tree for cutting. In U.S. Patent No. 103557849A (Rapid Mountainous Individual Tree Absolute Positioning and Coordinate Correction Method Applied to Quickbird Images), trees are located by satellite positioning and tachymeter measurement. In WO 2010032496A1 (Tree information measuring method, tree information measuring device and program), the location of trees is determined by laser distance measurements. In WO 2017146641A1 (Positioning Method and Device for Growing Trees, Construction Elements or Geological Features), locations are measured by angles and distances as an image interpretation. In addition, signals can be placed in the terrain as shown in the pictures. The method cannot be used to measure plots, which is the subject of the present invention. In CN 104636906A (Continuous forest Inventory method based on Windows Mobile), positioning is accomplished by satellite positioning.
    In addition to previous tree measurement methods, for example, the use of a laser scanner for 3D tree measurements (Xinlian Liang, Ville Kankare, Juha Hyyppä, Yunsheng Wang, Antero Kukko, Henrik Haggren, Xiaowei Yu, Harri Kaartinen, Anttoni Jaakkola, Fengying Guan, Markus Holopainen, , Terrestrial laser scanning in forest inventories, ISPRS Journal of Photogrammetry and Remote Sensing, 115: 63-77), use of mobile laser scanning in automatic measurement of trees (Xinlian Liang, Antero Kukko, Harri Kaartinen, Juha Hyyppä, Xiaowei Yu, Anttoni Jaakkola, Yunsheng Wang , 2014. Possibilities of a personal laser scanning system for forest mapping and ecosystem services, Sensors 14: 1228-1249), use of a smartphone-based camera in plot measurements (Mikko Vastaranta, Eduardo Gonzalez Latorre, Ville Luoma, Ninni Saarinen, Markus Holopainen, Juha Hyyppä, 2015. Evaluation of a Smartphone App for Forest Sample Area Measurements. Forests 6: 1179-1194) and l The use of an on-premise laser scanner for measurement of test stands (Anttoni Jaakkola, Juha Hyyppä, Xiaowei Yu, Antero Kukko, Harri Kaartinen, Xinlian Liang, Hannu Hyyppä, Yunsheng Wang, 2017. Autonomous Collection of Forest Field Reference - The First Step with UAV Laser Scanning . Remote Sensing 9 (8): 785).
    In field surveying of trees, a number of plot-specific data is measured or otherwise recorded, for example, information on plot location and site. In addition, tree-specific data such as diameter from chest height, length, tree species, etc. are measured and recorded. The present invention provides position data for each tree measured. The position of the tree is defined as the position of the center of the trunk at chest height. The present invention is the first method by which the location of trees can be measured in free-form and arbitrarily large plots. The invention differs significantly from other tree positioning and measurement methods and is, in fact, an integrated tree measuring and positioning method. The invention utilizes trilateration-based positioning known per se and radiolocation methods known per se.
    SUMMARY OF THE INVENTION
    The invention relates to a method and a device for measuring the location and properties of individual trees in forest plots for forest inventory purposes.
    The method and the device can automate the measurement of locations in the area-based inventory plot measurements. The invention relates to a first method and apparatus for measuring the location of trees in free-form and arbitrarily large plots. The apparatus employs at least three radio frequency base stations, as well as one or more mobile transceivers, an inertia sensor, and a magnetometer. The distance measurement from the base stations is based on the pulse travel time. A local coordinate system is established for distances between base stations by minimizing the amount of error. The mobile station travels to the trees to be measured, logs the tree species and other information, measures the height of the chest, and records the distances to all base stations within range.
    Location measurement utilizes radio distance range measurement. The use of radio waves for distance measurement has long been in use, but only in recent years has the Ultra Wide Band (UWB) bandwidth achieved such a high bandwidth that it has achieved centimeters of accuracy. In the UWB range (3-10 GHz), up to 500 MHz bandwidth can be used, which enables very fast rise and fall times of rectangular pulses. In this case, the pulse travel time to positioning can be measured with sufficient accuracy. Unidirectional travel time measurement requires extremely accurate clock synchronization, which is not feasible with lightweight and off-road equipment using today's technology. Measuring the round trip time does not require accurate synchronized clocks, but the accuracy of a normal quartz crystal clock is sufficient.
    Positioning based on distance measurements is called trilateration. If the distances of the object to be located to at least three known locations (base stations) are known, the coordinates of the object can be solved in the plane. If distances to multiple objects are known, the problem is overdetermined and can be solved by minimizing the amount of error, for example, by the least squares method. This gives an estimate of the accuracy of the positioning in addition to the approximate location.
    In terrain conditions it is impractical to determine a known location for very many points, for example by satellite positioning. In the present invention, base stations themselves measure their own positions in the local free coordinate system. Similarly, tree positions are determined during the measurement process with respect to this local coordinate system. The local coordinate system is linked to the national coordinate system (in Finland, for example, ETRS-TM35FIN) by measuring the appropriate number of common points in both systems, local and national, and calculating the conversion between the systems.
    The result is an integrated method for measuring the forest plot and determining the location and properties of individual trees using a radio wave instrument. The process is most preferably carried out in the following steps:
    1. The FMC shall be covered by radio frequency base stations located at arbitrary locations within the FMC.
    2. The mobile station travels to the trees to be measured, registers the tree species and other information as possible, measures the height of the chest, and records the distances to all base stations in the coverage area.
    3. A local coordinate system is established for distances between base stations by minimizing the amount of error.
    4. From the distances measured by the mobile station to the base stations, the location of the mobile station in the local coordinate system is calculated
    5. The position of the mobile station is converted to a national coordinate system using common points
    6. Using the fused result of the magnetometer and the inertial sensor, and measuring the diameter of the tree, a correction vector is calculated for the position of the mobile station, thus obtaining the position of the center of the tree at chest height.
    The invention has realized e.g. use of radio positioning in forest measurement; integrated tree measurement and positioning method; In the present invention, in measuring the length of a tree, distance measurement is done by radio measurement, whereby only angular measurement at the top of the tree is sufficient. This makes the measurement process faster, simpler and more accurate
    In the following, the invention will be described in detail by way of figures and examples, which are not intended to limit the invention in any way.
    PATTERNING
    Figure 1 is a plan view of the method and apparatus. The mobile station 100 consists of a data acquisition and processing computer 100, a radio transceiver 104, which determines distances to other base stations, measuring scissors or other diameter measuring devices 102, an inertia sensor 106, and a magnetometer 108. At least 4 base stations (112-122) are freely mounted.
    Fig. 2 is a schematic view of a measuring event in which mobile station 100 measures tree diameter, registers tree species, and measures position and distances to other trees using base stations 112-122.
    Figure 3 illustrates the steps of measuring: a) locating base stations in area 302, b) initializing the mobile station 304, c) measuring each tree 306, consisting of sub-phases tree species registration 308, chest height measurement 310, and distance measurement 312. The local coordinate system is connected to the global coordinate system by using common measurement points. For example, the least squares can minimize errors.
    DETAILED DESCRIPTION OF THE INVENTION
    Figure 3 illustrates, at a rough level, a measurement event according to the invention at the block diagram level.
    The coverage area is covered by base stations by placing them at arbitrary targets within the coverage area. Equal placement is desirable, but not very accurate. Base stations can be placed on pedestals or attached to tree branches or trunks. The minimum number of base stations is 4, but the system performs better with larger number of base stations (for example, 9-25), because it provides more redundancy to the observations, which makes the operation more fault tolerant and produces more accurate results. There is a maximum operating distance between base stations, as well as between a mobile station and base stations, which depends on the frequency used and other radio parameters (e.g., transmit power used), and obstacles on the radio path, such as trees. Not all base stations need to connect to every other base station, and the mobile station may not need to connect to every base station. It is enough that connections are always made to a certain minimum number of other stations, for example to at least four other stations. It's a good idea to build a network so dense that there is always enough redundancy to get accurate results.
    Once the base stations are located in the area to be measured, a mobile station is started which begins to search for the base stations. The mobile station is subjected to a series of movements that initialize the inertia sensors. If not all base stations are found, the mobile station can walk around in the vicinity of the base stations.
    Once the base stations are found, measurement delivery can be started. The measuring instrument travels to the tree to be measured, records the tree species and any other information, measures the height of the chest, and records the distances to all base stations within range. Whenever a tree measurement delivery is not in progress, for example when moving from one tree to be measured to another, the mobile station initiates measurements of distances between base stations. In turn, a measurement of the distance from each base station in the coverage area is requested to each of the other base stations within its coverage area. During the measurement of the test area, a large number of distance observations are made between base stations. Overdetermination improves the accuracy of the result and eliminates possible errors.
    A local coordinate system is formed of the distances between base stations by minimizing the sum of errors, for example the sum of squares of errors. This can be done in either plane (2D) or space (3D). The space solution requires height variations in positioning of base stations and greater redundancy in observations. In a local coordinate system, there are freely definable unknowns as follows: In a plane solution, the origin of the local coordinate system must be freely definable, as is the rotation of the coordinate system. This can be accomplished by giving one base station coordinates (0.0) and another base station (x1.0). For all others, coordinates are determined relative to these two base stations. In addition, the height of three base stations can be fixed in the space solution. For example, these can be given the coordinates of 2 m.
    The local coordinate system is linked to the national coordinate system by using common points. This can be accomplished by measuring the locations of the base stations, but it is more practical to measure common points in both systems. When using static satellite positioning, the position of the satellite positioning mast on the mobile station is measured near the corners of the area. At least two measurements are sufficient for level measurement. Here too, it is advisable to use sufficient overdetermination to improve accuracy and detect potential errors.
    The minimum number can be considered as one satellite position in four corners of the area.
    Based on the common points, the conversion between the local and national coordinates is calculated. At the very least, the transformation is transfer and rotation. It can be a plane-to-Helmer transformation with a scale conversion in addition to the above. The local coordinate system is accurate to scale without measurement error. If the area to be measured is located on a slope, a scaling error will occur which is not the same in different directions. If there are enough common points, a more flexible conversion can be used. A 3D-Helmert transform can be used as a space solution (e.g., Guobin Chang, 2016. Closed form least-squares solution to 3D symmetric Helmert Transformation with Rotational Invariant Covariance Structure. Acta Geodaetica et Geophysica, 51 (2): 237-244).
    Once the known coordinates for the base stations are obtained, the positions are calculated from the distance measurements of the mobile station by minimizing error amounts, for example by the least squares method.
    The mobile station is disposed within the measuring means, generally the measuring scales used for measuring the diameter. Naturally, the antenna used as the reference point for the measurement cannot be located inside the frame to be measured, but outside the frame within the measuring device. There is a transition vector between the position of the antenna and the center of the target of the measurement, which depends on the direction of the measurement in the national coordinate system and also on the diameter of the tree to be measured. For each measurement, the mobile station registers directional angles based on the fused result of the magnetometer of the device and the inertial sensor. The scissors measure the diameter of the frame. Position correction is the trigonometric rotation of the direction of the vector, which is a constant vector plus half the diameter of the body. Position correction is added to the measured position to give an accurate approximation to the center of the body at chest height.
    All of the above calculation operations can be performed as a post-calculation after the test area measurement has been completed. It is also possible to organize the calculations in real time as soon as the measurements have been made.
    Wood length measurement. Nowadays, tree lengths (the height of the top of the crown) are measured using an ultrasonic and gravity angle measuring device. The device first measures the distance to the ultrasonic transponder, placed near the tree trunk at chest height. The angle at the top of the tree is then measured and the measuring device trigonometically calculates an estimate of the length of the tree.
    In the present invention, distance measurement is made by radio measurement, whereby only angular measurement at the top of the tree is sufficient. This makes the measurement process faster, simpler and more accurate.
    权利要求:
    Claims (12)
    [1]
    1. A method for measuring a forest plot and determining the location and characteristics of individual trees by means of a radio wave apparatus characterized by:
    (a) The forest cover to be measured shall be covered by radio frequency base stations by placing them at arbitrary targets within the measuring range.
    (b) The mobile station shall travel to the trees to be measured, record the species of tree and any other information, measure the height of the chest and record the distances to all base stations in the coverage area.
    c) Establishing a local coordinate system of distances between base stations by minimizing the amount of error.
    [2]
    Method according to claim 1, characterized in that step a) is carried out by at least three radio frequency base stations
    [3]
    Method according to claim 1, characterized in that the distance measurement of step b) between the two base stations is based on the pulse propagation time.
    [4]
    Method according to one of Claims 1 to 3, characterized in that, in step b), for each measurement, the mobile station registers directional angles based on the fused result of the mobile station magnetometer and the inertia sensor.
    [5]
    Method according to claim 4, characterized in that for each measured tree, position information is obtained by trilateration in the local coordinate system.
    [6]
    Method according to one of Claims 1 to 5, characterized in that the trilateration can be solved by minimizing the amount of error, for example by the least squares method, and if distances are known to more than three objects, the problem is overestimated.
    [7]
    Method according to one of Claims 1 to 6, characterized in that in the invention the base stations themselves measure their own positions in the local free coordinate system.
    [8]
    A method according to claim 7, characterized in that the local coordinate system is bound to the national coordinate system by measuring a suitable number of common points in both systems, local and national, and calculating the conversion between the systems.
    [9]
    The method according to claim 1, characterized in that in step b) the mobile station is disposed in the measuring means, generally the measuring scissors used for measuring the diameter, and the antenna being the reference point for the measurement cannot of course be located inside the measuring body but outside of the measuring device. the direction of measurement in the National Coordinate System and also the diameter of the tree to be measured.
    [10]
    Method according to claim 9, characterized in that the magnetometer and the inertia sensor are used to determine the direction of the transfer vector between the antenna and the center of the body.
    [11]
    Method according to one of Claims 1 to 8, characterized in that the measurement of the length of the selected trees is carried out such that the distance measurement to the selected tree is done by radio measurement, whereby only an angular measurement on the top of the tree is sufficient.
    [12]
    Method according to one of Claims 1 to 11, characterized in that the location of the trees and the tree identifiers are calculated by means of a computer program or an embedded processor.
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