CN113109832A - Bamboo degree judgment method based on laser echo intensity - Google Patents
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- 235000017166 Bambusa arundinacea Nutrition 0.000 title claims abstract description 78
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Abstract
The invention discloses a moso bamboo degree judgment method based on laser echo intensity, and relates to the technical field of laser moso bamboo degree judgment. The method comprises the steps of establishing a sample plot of a rectangular area, and erecting a three-dimensional laser scanner by taking the periphery and the center of the sample plot as a measuring station; extracting point cloud data from the middle of each section of bamboo joint in a window of 2cm by 2 cm; correcting the distance measurement value and the incident angle of the laser echo strength value; and obtaining a fitting model of bamboo joint numbers of bamboo stalks with different bamboo degrees and the laser echo intensity value. The method comprises the steps of obtaining point cloud data of the middle parts of all bamboo sections of the moso bamboo through a three-dimensional laser scanner, and correcting distance measurement values and incidence angles of laser echo intensity values; calculating the average value of the laser echo intensity values after correction as the laser echo intensity value of the bamboo joint section, and obtaining a fitting model of bamboo joint numbers of bamboo stalks with different bamboo degrees and the laser echo intensity value; the bamboo degree of the moso bamboo is judged by calculating whether the laser echo intensity value of each section of the moso bamboo meets the fitting model, and the discrimination efficiency and accuracy of the bamboo degree of the moso bamboo are improved.
Description
Technical Field
The invention belongs to the technical field of laser moso bamboo degree judgment, and particularly relates to a moso bamboo degree judgment method based on laser echo intensity.
Background
The moso bamboo as a large-scale scattered bamboo seed of Phyllostachys of Bambusoideae of Gramineae has the characteristics of fast growth, high yield, good quality, wide application, short felling period, early yield and high economic value, and is the bamboo seed which is widely distributed in the world, has the largest cultivation area and has obvious economic benefit at present. The xylem of the plant is different from that of a common arbor tree species in that the xylem of the plant has a traditional annual ring to determine the age unlike gymnosperms or dicotyledons. The age of the bamboo plant of the moso bamboo (bamboo age for short) has a close relationship with the living strength, the metabolic capability, the renewal capability and the mechanical properties of the bamboo, so that the accurate judgment of the age of the moso bamboo has great significance for cultivation management, felling utilization, scientific research and the like of the moso bamboo, and is one of the essential bases.
The age of bamboo is commonly expressed by degree, one degree represents two years, the moso bamboo grown from one to two years is called first degree bamboo, the moso bamboo grown from three to four years is called second degree bamboo, and so on. The currently used bamboo age determination methods mainly comprise three methods:
1) the bamboo number marking method comprises the following steps: the method can accurately judge the age of the moso bamboo by marking the bamboo forming age on the bamboo stalk when the moso bamboo is formed by bamboo shoots, but the workload is large and the condition of label leakage is easy to cause;
2) bamboo stalk color skin method: as the moso bamboo culm grows older, its surface color, wax layer and parasitic lichen characteristics of the moso bamboo change. The first-degree bamboo stalks are cyan and have white fluff adhered to the surfaces, the second-degree bamboo stalks are green yellow, the third-degree bamboo stalks are yellow skins, and the fourth-degree bamboo stalks are over 6 years old and have yellow-red colors. The method is simple and easy to identify, but the age of the moso bamboo is easy to be judged by mistake;
3) identifying branch leaf-changing habit: the twig of the first generation moso bamboo is an unshaped twig, new branches and leaves grow with the age of the mother bamboo, old branches fall off in the process of the growth and development of the new branches, traces are left on the branches, and the formula for calculating the age of the moso bamboo can be obtained by induction and arrangement, wherein the age of the moso bamboo is (2 multiplied by the number of the traces of the branches) + the age of the small branches with leaves. The method can accurately calculate the real age of the moso bamboos, but requires the patience analysis, needs to have rich plant knowledge and practical experience, is easily influenced by external environment mutation, and cannot be used for accurately judging the age of the moso bamboos under the influence of the external environment mutation such as locust disasters, fire drought and waterlogging and the like.
The invention provides a moso bamboo degree judging method based on laser echo intensity, aiming at efficiently judging the moso bamboo degree.
Disclosure of Invention
The invention aims to provide a moso bamboo degree judging method based on laser echo intensity, which is used for solving the problems in the background technology.
In order to solve the technical problems, the invention is realized by the following technical scheme:
the invention relates to a moso bamboo degree judging method based on laser echo intensity, which comprises the following steps:
a00: establishing a sample plot of a rectangular area, and erecting a three-dimensional laser scanner by taking the periphery and the center of the sample plot as a measuring station;
a01: selecting 8 plants of one to seven-year-old moso bamboos, cutting the parts from the lower branches of the moso bamboos to the bamboo stems on the ground, and extracting point cloud data from the middle part of each section of bamboo joint in a window of 2cm to 2 cm; the point cloud data consists of a plurality of laser echo intensity values;
a02: correcting the distance measurement value and the incident angle of the laser echo strength value;
a03: calculating the average value of the corrected laser echo intensity values as the laser echo intensity value of the section of bamboo joint;
a04: obtaining fitting models of bamboo joint numbers of bamboo stalks with different bamboo degrees and laser echo intensity values:
y1＝0.48x2-17.937x-1014.5
y2＝-0.4425x2+12.983x-1157.8
y3＝-0.0547x2-4.2539x-1050.8
y4＝0.0016x6-0.0849x5-19.105x3+109.77x2-315.42x-680.66
wherein, y1、y2、y3、y4Respectively fitting laser echo strength values of the bamboo stalks of one to four degrees; and x is a bamboo knot number.
As a preferred technical solution, a00 further includes placing 3 plane targets in the sample chamber and performing station-finding stitching through the plane targets.
As a preferred technical solution, a02 specifically includes the following processes:
b00: neglecting the influence of the reflectivity of the object and the atmospheric attenuation on the laser echo intensity value, and obtaining a simplified laser echo intensity empirical model: i ═ Gf (θ) f (r);
wherein, I is the original laser echo intensity value, G is a constant, f (theta) is an incidence angle correction function, and f (R) is a distance correction function;
b01: fixing the incidence angle theta of the three-dimensional laser scanner, selecting a 3In plane target as a scanning object, changing the distance between the target and the scanner by a fixed step length, keeping the center of an electric detector of the three-dimensional laser scanner and the center of the target at the same height for scanning, and obtaining the relation between different distance measurement and laser echo intensity values under the fixed incidence angle;
b02: fixing the incident distance R of the three-dimensional laser scanner, rotating the target plane by a fixed step length, changing the incident angle of the scanned target, and acquiring the relationship between different incident angles and laser echo intensity values at a fixed distance;
b03: and establishing a piecewise fitting function between the laser echo intensity value and the ranging and incidence angles, calculating model parameters, and correcting the laser echo intensity value.
As a preferable technical scheme, a target plane in B01 is vertical to the ground, and an incidence angle theta is kept to be 0; when R is less than or equal to 10m, the step length is 1 m; when R is more than 10m, the step length is 5 m.
As a preferable technical scheme, the distance between the three-dimensional laser scanner in B02 and the target is 10 m; when theta is less than or equal to 40 degrees, the step length is 10 degrees; theta > 40 deg. and the step size is 5 deg..
As a preferred technical solution, B03 specifically includes the following processes:
c00: selecting point cloud data with the distance of 8-10m and the incident angle of 40-50 degrees to perform polynomial fitting, and acquiring an extreme point of a piecewise fitting function as a critical point; wherein the distance correction critical point is 9.9m, and the angle correction critical point is 45 degrees;
c01: obtaining a laser echo intensity value correction formula containing distance and incident angle:
wherein, IsFor the corrected laser echo intensity value, (X, Y, Z) is the three-dimensional coordinate of the point cloud space, RsTo reference the distance, θsAs a reference angle, αiAnd betaiAre all polynomial coefficients, | n | is the modulus of the normal vector; i is the original laser echo intensity; k is a system constant, theta is an incident angle, and R is an incident distance;
c02: obtaining a point cloud normal vector n ═ (n) according to a K nearest neighbor domain method1,n2,n3) Solving the cosine value of the point incidence angle according to the cosine law, and solving the inverse cosine function of the cosine value to obtain the corresponding incidence angle theta;
c03: performing polynomial fitting on f (theta), f (R) by using a least square method, selecting different indexes N, and determining N by using the root mean square error RMSE of points participating in fitting and fitting functions as a selection basis of f (theta), f (R)1＝4，N2＝3，N3＝3，N4＝4。
As a preferable technical solution, when calculating an average value of a plurality of corrected laser echo intensity values in a03, a laser echo intensity queue is formed by arranging the plurality of corrected laser echo intensity values according to intensity, and the head 10% and the tail 10% of the queue are removed.
The invention has the following beneficial effects:
the method comprises the steps of obtaining point cloud data of the middle parts of all bamboo sections of the moso bamboo through a three-dimensional laser scanner, and correcting distance measurement values and incidence angles of laser echo intensity values; calculating the average value of the laser echo intensity values after correction as the laser echo intensity value of the bamboo joint section, and obtaining a fitting model of bamboo joint numbers of bamboo stalks with different bamboo degrees and the laser echo intensity value; the bamboo degree of the moso bamboo is judged by calculating whether the laser echo intensity value of each section of the moso bamboo meets the fitting model, and the discrimination efficiency and accuracy of the bamboo degree of the moso bamboo are improved.
Of course, it is not necessary for any product in which the invention is practiced to achieve all of the above-described advantages at the same time.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a flowchart of a method for determining bamboo degree based on laser echo intensity according to the present invention;
FIG. 2 is a flow chart illustrating the distance measurement and incident angle correction of the laser echo intensity value in A02 according to the present invention;
FIG. 3 is a flow chart of the present invention B03 for calculating model parameters and correcting the laser echo intensity values;
FIG. 4 is a distribution diagram of the three-dimensional laser scanner in a rectangular plot in accordance with the present invention;
FIG. 5 is a schematic diagram of extracting point cloud data from a window of 2cm by 2cm at the middle of a bamboo joint in the present invention;
FIG. 6 is a graph showing the fitting results of the fitting model of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, the present invention is a method for determining bamboo degree of moso bamboo based on laser echo intensity, including the following steps:
a00: referring to fig. 4, a sample plot of a rectangular area is established, a three-dimensional laser scanner is erected with the periphery and the center of the sample plot as a measuring station, and overlapping parts are uniformly scanned during scanning; specifically, the above-mentioned pattern is 20m × 20m, and 188 moso bamboos are cumulatively scanned; arranging 3 plane targets in the sample plot, and carrying out station measurement splicing through the plane targets, wherein the splicing error is controlled within 1 mm; in addition, each wood ruler is manually checked, and the information of the age, the diameter of breast height (1.3 m) and the height of bamboo of each moso bamboo is recorded;
a01: selecting 8 plants of one to seven-year-old moso bamboos, cutting the parts from the lower branches of the moso bamboos to the bamboo stems on the ground, and extracting point cloud data from the middle part of each section of bamboo joint in a window of 2cm to 2cm, as shown in figure 5; the point cloud data consists of a plurality of laser echo intensity values; when the laser echo intensity value correcting device is actually used, when the average value of a plurality of corrected laser echo intensity values is calculated, a laser echo intensity queue is formed by arranging the plurality of corrected laser echo intensity values according to the intensity, and 10% of the head of the queue and 10% of the tail of the queue are removed so as to reduce errors;
a02: acquiring point cloud data by adopting a Fence function in Leica matching software Cyclone, and correcting a distance measurement value and an incident angle of a laser echo intensity value;
a03: calculating the average value of the corrected laser echo intensity values as the laser echo intensity value of the section of bamboo joint;
a04: obtaining fitting models of bamboo joint numbers of bamboo stalks with different bamboo degrees and laser echo intensity values:
y1＝0.48x2-17.937x-1014.5,R2＝0.9611
y2＝-0.4425x2+12.983x-1157.8,R2＝0.9231
y3＝-0.0547x2-4.2539x-1050.8,R2＝0.9546
y4＝0.0016x6-0.0849x5-19.105x3+109.77x2-315.42x-680.66,R2＝0.9466
wherein, y1、y2、y3、y4Respectively fitting laser echo strength values of the bamboo stalks of one to four degrees; x is the bamboo knot number; furthermore, the fitting order is determined while ensuring the fitting model correlation coefficient R2Above 0.95, the fitting result of the function model is accurate, and the fitting result is shown in figure 6.
As a preferred embodiment, please refer to fig. 2, a02 specifically includes the following steps:
actually, the point cloud laser echo intensity represents the reflection spectrum information of the target to the laser, and the phenomenon of same object and different spectrum or same spectrum of foreign objects can occur under the influence of various factors such as the system characteristics of a scanner, atmospheric attenuation, the physical properties of the surface of the target, the scanning environment and the like. Therefore, various factors influencing the point cloud laser echo intensity data need to be corrected aiming at the phenomenon; the reflectivity of the plane target is high, so that the reflectivity of the target can be regarded as 100%, the influence of the reflectivity of an object on the echo intensity of the point cloud laser is ignored, and the influence of the reflectivity rho on the echo intensity of the laser is regarded as a fixed constant; in the ground scanning process, the influence of atmospheric attenuation on the laser echo intensity can be ignored due to the fact that the laser measuring distance is small.
B00: neglecting the influence of the reflectivity of the object and the atmospheric attenuation on the laser echo intensity value, and obtaining a simplified laser echo intensity empirical model: i ═ Gf (θ) f (r);
wherein, I is the original laser echo intensity value, G is a constant, f (theta) is an incidence angle correction function, and f (R) is a distance correction function;
b01: fixing the incidence angle theta of the three-dimensional laser scanner, selecting a 3In plane target as a scanning object, changing the distance between the target and the scanner by a fixed step length, keeping the center of an electric detector of the three-dimensional laser scanner and the center of the target at the same height for scanning, and obtaining the relation between different distance measurement and laser echo intensity values under the fixed incidence angle; specifically, the target plane is perpendicular to the ground, and the incidence angle theta is kept to be 0; when R is less than or equal to 10m, the step length is 1 m; when R is more than 10m, the step length is 5 m;
b02: fixing the incident distance R of the three-dimensional laser scanner, rotating the target plane by a fixed step length, changing the incident angle of the scanned target, and acquiring the relationship between different incident angles and laser echo intensity values at a fixed distance; specifically, the distance between the three-dimensional laser scanner and the target is 10 m; when theta is less than or equal to 40 degrees, the step length is 10 degrees; theta is more than 40 degrees, and the step length is 5 degrees;
b03: and establishing a piecewise fitting function between the laser echo intensity value and the ranging and incidence angles, calculating model parameters, and correcting the laser echo intensity value.
As a preferred embodiment, please refer to fig. 3, B03 specifically includes the following steps:
in fact, for the Leica C05 ground three-dimensional laser scanner, the laser echo intensity of the point cloud appears as two distinct peak regions in the range of 0m-30m, roughly in a linear relationship within 0 ° -50 °, drops significantly after 50 °, and after 50 °, the laser echo intensity rapidly decreases with increasing incidence angle. Compared with the ranging factor, the influence of large-angle measurement on the laser echo intensity is more obvious. Therefore, in the test process, the relation between the laser echo intensity and two factors, namely the laser ranging value and the incident angle, is considered to establish a piecewise fitting function relation, so that model parameters are calculated, and the point cloud laser echo intensity value is corrected;
c00: selecting point cloud data with the distance of 8-10m and the incident angle of 40-50 degrees to perform polynomial fitting, and acquiring an extreme point of a piecewise fitting function as a critical point; wherein the distance correction critical point is 9.9m, and the angle correction critical point is 45 degrees;
c01: obtaining a laser echo intensity value correction formula containing distance and incident angle:
wherein, IsFor the corrected laser echo intensity value, (X, Y, Z) is the three-dimensional coordinate of the point cloud space, RsFor a reference distance (10 m in the present embodiment), θsIs a reference angle (0 degree in the present embodiment), alphaiAnd betaiAre all polynomial coefficients, | n | is the modulus of the normal vector; i is the original laser echo intensity; k is a system constant, theta is an incident angle, and R is an incident distance;
c02: obtaining a point cloud normal vector n ═ (n) according to a K nearest neighbor domain method1,n2,n3) Solving the cosine value of the point incidence angle according to the cosine law, and solving the inverse cosine function of the cosine value to obtain the corresponding incidence angle theta;
c03: carrying out polynomial fitting on f (theta), f (R) by using a least square method, selecting different indexes N, and using root mean square errors RMSE of points participating in fitting and fitting functions as selection basis of f (theta), f (R); see Table 1 for details, determination of N1＝4，N2＝3，N3＝3，N 44, avoiding overfitting while ensuring f (theta), f (r) to have higher fitting accuracy; in particular, the method comprises the following steps of,
table 1 shows the piecewise polynomial function order selection and fitting function root mean square error:
table 2 shows the standard deviation of the target laser echo intensities before and after correction:
the average laser echo intensities of the target after the distance and the incidence angle are corrected tend to be consistent, the standard deviation of the average value of the laser echo intensities of the point cloud before and after the correction is calculated is shown in table 2, the standard deviation before and after the correction is obviously reduced, and the correction result is proved to be practical and effective.
When the device is actually used, point cloud data of the middle parts of all bamboo sections of the moso bamboo are obtained through the three-dimensional laser scanner, and distance measurement values and incident angle correction are carried out on laser echo intensity values; calculating the average value of the laser echo intensity values after correction as the laser echo intensity value of the bamboo joint section, and obtaining a fitting model of bamboo joint numbers of bamboo stalks with different bamboo degrees and the laser echo intensity value; the bamboo degree of the moso bamboo is judged by calculating whether the laser echo intensity value of each section of the moso bamboo meets the fitting model, and the discrimination efficiency and accuracy of the bamboo degree of the moso bamboo are improved.
It should be noted that, in the above system embodiment, each included unit is only divided according to functional logic, but is not limited to the above division as long as the corresponding function can be implemented; in addition, specific names of the functional units are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present invention.
In addition, it is understood by those skilled in the art that all or part of the steps in the method for implementing the embodiments described above may be implemented by a program instructing associated hardware, and the corresponding program may be stored in a computer-readable storage medium.
The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims (7)
1. The moso bamboo degree judging method based on the laser echo intensity is characterized by comprising the following steps of:
a00: establishing a sample plot of a rectangular area, and erecting a three-dimensional laser scanner by taking the periphery and the center of the sample plot as a measuring station;
a01: selecting 8 plants of one to seven-year-old moso bamboos, cutting the parts from the lower branches of the moso bamboos to the bamboo stems on the ground, and extracting point cloud data from the middle part of each section of bamboo joint in a window of 2cm to 2 cm; the point cloud data consists of a plurality of laser echo intensity values;
a02: correcting the distance measurement value and the incident angle of the laser echo strength value;
a03: calculating the average value of the corrected laser echo intensity values as the laser echo intensity value of the section of bamboo joint;
a04: obtaining fitting models of bamboo joint numbers of bamboo stalks with different bamboo degrees and laser echo intensity values:
y1＝0.48x2-17.937x-1014.5
y2＝-0.4425x2+12.983x-1157.8
y3＝-0.0547x2-4.2539x-1050.8
y4＝0.0016x6-0.0849x5-19.105x3+109.77x2-315.42x-680.66
wherein, y1、y2、y3、y4Respectively fitting laser echo strength values of the bamboo stalks of one to four degrees; and x is a bamboo knot number.
2. The method of claim 1, wherein a00 further comprises placing a 3-plane target in the sample chamber and performing station-finding stitching through the plane target.
3. The method for determining the bamboo degree based on the laser echo intensity of claim 2, wherein a02 specifically comprises the following steps:
b00: neglecting the influence of the reflectivity of the object and the atmospheric attenuation on the laser echo intensity value, and obtaining a simplified laser echo intensity empirical model: i ═ Gf (θ) f (r);
wherein, I is the original laser echo intensity value, G is a constant, f (theta) is an incidence angle correction function, and f (R) is a distance correction function;
b01: fixing the incidence angle theta of the three-dimensional laser scanner, selecting a 3In plane target as a scanning object, changing the distance between the target and the scanner by a fixed step length, keeping the center of an electric detector of the three-dimensional laser scanner and the center of the target at the same height for scanning, and obtaining the relation between different distance measurement and laser echo intensity values under the fixed incidence angle;
b02: fixing the incident distance R of the three-dimensional laser scanner, rotating the target plane by a fixed step length, changing the incident angle of the scanned target, and acquiring the relationship between different incident angles and laser echo intensity values at a fixed distance;
b03: and establishing a piecewise fitting function between the laser echo intensity value and the ranging and incidence angles, calculating model parameters, and correcting the laser echo intensity value.
4. The method for determining the degree of bamboo by using the echo intensity of laser according to claim 3, wherein the target plane in B01 is perpendicular to the ground, and the incident angle θ is kept to be 0; when R is less than or equal to 10m, the step length is 1 m; when R is more than 10m, the step length is 5 m.
5. The method of claim 3, wherein the three-dimensional laser scanner in B02 is mounted at a distance of 10m from the target; when theta is less than or equal to 40 degrees, the step length is 10 degrees; theta > 40 deg. and the step size is 5 deg..
6. The method for determining the bamboo degree based on the laser echo intensity of claim 3, wherein B03 specifically comprises the following steps:
c00: selecting point cloud data with the distance of 8-10m and the incident angle of 40-50 degrees to perform polynomial fitting, and acquiring an extreme point of a piecewise fitting function as a critical point; wherein the distance correction critical point is 9.9m, and the angle correction critical point is 45 degrees;
c01: obtaining a laser echo intensity value correction formula containing distance and incident angle:
wherein, IsFor the corrected laser echo intensity value, (X, Y, Z) is the three-dimensional coordinate of the point cloud space, RsTo reference the distance, θsAs a reference angle, αiAnd betaiAre all polynomial coefficients, | n | is the modulus of the normal vector; i is the original laser echo intensity; k is a system constant, theta is an incident angle, and R is an incident distance;
c02: obtaining a point cloud normal vector n ═ (n) according to a K nearest neighbor domain method1,n2,n3) Solving the cosine value of the point incidence angle according to the cosine law, and solving the inverse cosine function of the cosine value to obtain the corresponding incidence angle theta;
c03: performing polynomial fitting on f (theta), f (R) by using a least square method, selecting different indexes N, and determining N by using the root mean square error RMSE of points participating in fitting and fitting functions as a selection basis of f (theta), f (R)1＝4，N2＝3，N3＝3，N4＝4。
7. The method for determining the degree of bamboo or bamboo on the basis of laser echo intensities according to claim 1, 3, 4, 5 or 6, wherein when the average value of the plurality of corrected laser echo intensity values is calculated in A03, the plurality of corrected laser echo intensity values are arranged according to the intensity to form a laser echo intensity queue, and the head 10% and the tail 10% of the queue are removed.
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