The method that unmanned plane LiDAR and random forest extract ginkgo biological physical characteristic
Technical field
The present invention relates to the fields such as forest resource monitoring and environmental factor investigation, specifically a kind of unmanned plane that passes through is generated
The method for extracting biophysical properties Random Forest model.
Background technique
The extraction of accurate artificial forest biophysical properties, for forest inventory investigation, Forest Productivity estimation and biology
Study on Diversity is of great significance.These information, which have, simultaneously can be used for exploring the forest space regularity of distribution, and can to forest
Continuous production operation, raising Forestry Carbon Mitigation is horizontal and local area ecological balance is maintained to provide data support and practical advice.
Conventional artificial forest biophysical properties extraction depends on ground investigation method, and time-consuming effort only can
The data on " point " are obtained, precision is not often high, and is not easy to be promoted over a large area.Laser radar (LiDAR) technology
It is that a kind of active remote sensing technology of its return signal to body surface and is analyzed by transmitting laser pulse.It can be obtained by LiDAR
The information such as high-precision Forest Canopy structure and hayashishita landform.
In recent years, the research extracted based on LiDAR data biophysical properties are as follows: Montealegre etc. 2016 exists
" the Use of low point density ALS data to estimate stand- delivered on " Forestry " volume 89
Level structural variables in Mediterranean Aleppo pine forest ", the research is by having
Man-machine platform carries laser radar and obtains low-density point cloud data, and extraction height characteristic variable is assessing these variable importances
On the basis of combined ground measured data be extracted the biophysical characteristics of Mediterranean Region kahikatea.
Bottalico etc. 2017 in " International Journal of Applied Earth
Observations and Geoinformation " " the Modeling Mediterranean forest that delivers on volume 57
Structure using airborne laser scanning data ", the research use airborne laser radar data, pass through
LiDAR altitude feature variable is extracted, in conjunction with sample measured data, is extracted Italian needle artificial forest with linear model approach
Multiple biophysical properties.However, above method is all based on the biophysical properties of the LiDAR data of someone's machine platform
It extracting, point of use cloud packing density is all very low, and one group of characteristic variable is used only to extract biophysical properties, meanwhile,
More have no that the method for imparametrization is used for the extraction of plantation stand biophysical properties.
Summary of the invention
Goal of the invention: in view of the deficiency of the prior art, a kind of generated by unmanned plane is provided and extracts biological object
The method for managing characteristic Random Forest model, can effectively improve the extraction accuracy of biophysical properties on woodland.
Technical solution: in order to achieve the above-mentioned object of the invention, The technical solution adopted by the invention is as follows: one kind passes through unmanned plane
Generate the method for extracting biophysical properties Random Forest model, comprising the following steps:
1) LiDAR data acquisition is carried out by the LiDAR sensor that multi-rotor unmanned aerial vehicle is carried;And it is arranged simultaneously on ground
Sample, record sample interior ground trees strain tree, while measuring the diameter of a cross-section of a tree trunk 1.3 meters above the ground of every wood and setting high;And actual measurement chest is combined by Binary formula
Diameter and the high estimation accumulation of tree;The actual measurement diameter of a cross-section of a tree trunk 1.3 meters above the ground and tree height is combined to calculate ground biomass by different rate growth formula;
2) noise point for removing unmanned plane LiDAR original point cloud data removes non-ground points based on IDW filtering algorithm, so
Afterwards by calculating the average value of laser point height in each rubber member, digital elevation model is generated;Pass through the digital elevation of the generation
A cloud is normalized in model, the unmanned plane LiDAR point cloud data after being normalized;
3) three groups of canopy structure characteristic variables are extracted respectively;This three groups of characteristic variables include percentile altitude feature variable,
Each layer coverage characteristic variable and canopy volume and profile features variable;
4) the standing forest biophysical properties and unmanned plane LiDAR point cloud feature construction based on the actual measurement of existing ground are gloomy at random
Woods model;M variable is randomly generated for the binary tree on node in mtry value specified first, mtry value is for modeling
Point cloud feature quantity;Secondly, randomly selecting k sample set using bootstrap method with putting back to, k decision tree is formed, this
K decision tree forms Random Forest model, finally, predicts biophysical properties to the Random Forest model.
Wherein, the spatial resolution of the step 2) digital elevation model is 0.5m.
Wherein, the percentile altitude feature variable in the step 3) includes: that the canopy at H25, H50, H75 and H95 is high
Degree distribution percentile;Canopy point cloud is distributed the coverage CCmean of average height or more and the variation lines of canopy point cloud distribution
Number Hcv.
Wherein, each layer coverage characteristic variable described in the step 3) includes: cloud quantity in each percentage height
30th, 50th, 70th, 90th or more point account for the percentage of all the points cloud.
Wherein, the canopy volume in the step 3) and profile features variable refer to Weibull function to canopy height point
Cloth section is fitted to obtain 2 profile features amount Weibull α and Weibull β and each structured sort volume accounting of canopy,
Each structured sort volume accounting of the canopy refers to this four canopy structure classifications of open tier, photic zone, low photosphere and confining bed
Volume percentage.
This method uses leave one cross validation;Coefficient of determination R is set2, root-mean-square error RMSE, opposite root-mean-square error
The effect and estimation precision of rRMSE evaluation model fitting:
X in formulaiFor certain standing forest biophysical properties measured value;Average value is surveyed for certain standing forest biophysical properties;
For the model estimated value of certain standing forest biophysical properties;N for sample ground quantity;I is for some sample.
The utility model has the advantages that compared with prior art, the present invention having the advantage that
(1) present invention is all based on someone's machine platform compared to previous LiDAR, and the LiDAR point cloud density of acquisition is all very
It is low, and the characteristic variable type extracted is less, and this method can obtain highdensity LiDAR point cloud based on unmanned aerial vehicle platform, it is right
The filtering of unmanned plane LiDAR discrete point cloud data, interpolation generate digital elevation model, point cloud data normalized;Based on normalizing
Change unmanned plane LiDAR discrete point cloud and extracts multiple groups artificial forest canopy characteristic variable;Based on the multiple groups unmanned plane LiDAR all extracted
Artificial forest canopy characteristic variable and ground measured data, construct Random Forest model, and debugging model parameter assesses characteristic variable
Importance, final each standing forest biophysical properties of inverting;The inversion accuracy of artificial forest biophysical properties is helped to improve, and is had
Effect inhibits biophysical properties inverting " saturation " problem of forest cover degree height, the high standing forest of biomass;
(2) this method removes inverting standing forest biophysical properties using Random Forest model method;Compared to more traditional parameter
It needs to meet a series of a priori assumption between method variable, and can be become the feature of all extractions by Random Forest model
It measures input model and carries out operation, and Random Forest model can assess the importance of each characteristic variable, thus in high quality
It is extracted plantation stand biophysical properties.Meanwhile characteristic variable is not only conducive to by the random forest that above-mentioned data obtain
Mechanism explain, be also easy to carry out method transplanting, i.e., also may be employed in wildwood and scondary forest.
Detailed description of the invention
Fig. 1 is different densities ginkgo artificial forest true color photo effect picture;
Fig. 2 is different densities ginkgo artificial forest unmanned plane laser radar point cloud atlas;
Fig. 3 is the characteristic variable important relationship figure based on Random Forest model Different forest stands biophysical properties.
Specific embodiment
In the following with reference to the drawings and specific embodiments, the present invention is furture elucidated, and the present embodiment is with technical solution of the present invention
Premised under implemented, it should be understood that these examples are only for illustrating the present invention and are not intended to limit the scope of the present invention.
1) LiDAR data acquisition is carried out by the LiDAR sensor that multi-rotor unmanned aerial vehicle is carried.In ground setting sample,
Sample interior ground trees strain tree is recorded, while measuring the diameter of a cross-section of a tree trunk 1.3 meters above the ground of every wood and setting high.Accumulation combines actual measurement chest according to Binary formula
Diameter and tree height are estimated that ground biomass is calculated by the different rate growth formula combination diameter of a cross-section of a tree trunk 1.3 meters above the ground and tree height;
2) noise point for removing unmanned plane LiDAR original point cloud data first, is gone based on IDW filtering algorithm unless ground
Point generates digital elevation model (DEM), and space point then by calculating the average value of laser point height in each rubber member
Resolution is 0.5m.A cloud is normalized by the digital elevation model of generation, the unmanned plane after being normalized
LiDAR point cloud data;
3) three groups of canopy structure characteristic variables are extracted, i.e. percentile altitude feature variable, each layer coverage feature
Variable and canopy volume and profile features variable;
Wherein, percentile altitude feature variable includes: canopy height distribution percentile (H25, H50, H75, H95), hat
Coverage (CCmean) more than layer point cloud distribution average height, the coefficient of variation (Hcv) of canopy point cloud distribution;
Wherein, each layer coverage characteristic variable include: cloud quantity each percentage height (30th, 50th, 70th,
90th, i.e. D3, D5, D7, D9) more than point account for the percentage of all the points cloud;
Wherein, canopy volume includes: that Weibull function is fitted canopy height profile with profile features variable
Obtain 2 profile features amounts α, β (i.e. Weibull α and Weibull β);Each structured sort volume accounting of canopy, including open tier,
Photic zone, four canopy structure classifications of low photosphere and confining bed, the volume percentage of each canopy structure classification is (i.e.
OpenGap, Oligophotic, Euphotic, ClosedGap).
4) based on existing ground actual measurement standing forest biophysical properties and unmanned plane LiDAR point cloud feature construction for extracting
Predict the Random Forest model of biophysical properties;Building process is as follows: m variable is randomly generated in mtry value specified first
Binary tree on node, mtry value are the point cloud feature quantity for modeling;Secondly, being put using bootstrap method
It randomly selects k sample set with returning, forms k decision tree;Finally, according to the random forest that k decision tree finally forms, and it is right
Random Forest model carries out prediction and extracts biophysical properties.
This method uses leave one cross validation, the coefficient of determination (R2), root-mean-square error (RMSE), opposite root-mean-square error
(rRMSE) effect of evaluation model fitting and estimation precision:
X in formulaiFor certain standing forest biophysical properties measured value;Average value is surveyed for certain standing forest biophysical properties;
For the model estimated value of certain standing forest biophysical properties;N for sample ground quantity;I is for some sample.
Embodiment 1
Test block in the present embodiment is located at Jiangsu Province northern territory Pizhou City town Tie Fu, and geographical location is 34 ° of north latitude
33 ' 49 " -34 ° 34 ' 23 ", 118 ° 05 ' 1 of east longitude " -118 ° 06 ' 06 ".
The trial zone belongs to subhumid and temperate zones monsoon climate, and annual rainfall is about 903mm, and maximum rainfall concentrates on 7,8
Month plum rain season, year-round average temperature is about 13.9 DEG C, frost-free period 211 days, In The Soils be smolmitza earth, in acidity.
LiDAR data acquisition is carried out by the LiDAR sensor that multi-rotor unmanned aerial vehicle is carried first.It is provided according to history forest
The satellite remote-sensing image data that source survey data and early period obtain have chosen 5 pieces of 1 × 1km in ginkgo artificial forest Core distribution area
Square big plot, then in 5 sample ground according to the method for typical sampling the round sample that 9 pieces of radiuses are 15m is set,
The center on sample ground is positioned by Trimble GeoXH6000 Handhelds handhold GPS (in conjunction with JSCROS GPS wide area differential GPS system
System) it is positioned, precision is better than 0.5m.
During sample-plot survey, the Dan Mu of 5cm is greater than for the diameter of a cross-section of a tree trunk 1.3 meters above the ground, it is high to measure its diameter of a cross-section of a tree trunk 1.3 meters above the ground (diameter of a cross-section of a tree trunk 1.3 meters above the ground ruler measurement), tree one by one
(i.e. projector distance in two principal directions, uses tape measure with clear bole height (Vertex V ultrasonic wave and laser altimeter) and hat width
Measurement).By the individual tree information of actual measurement, summarize to obtain sample ground level stand characteristics, i.e. mean DBH increment, basal area, Lorey ' s
Mean stand height (using the basal area of each tree as weight, mean stand height that weighted sum obtains), the density of crop, accumulation
And ground biomass;Above-mentioned data see the table below 1.
Survey to 1 sample of table standing forest biophysical properties information summary sheet
When data prediction, the noise point of unmanned plane LiDAR original point cloud data is removed first, is based on IDW filtering algorithm
Non-ground points are removed, then by calculating the average value of laser point height in each pixel, are generated digital elevation model (DEM)
(spatial resolution 0.5m).And a cloud is normalized in the digital elevation model by generating, after obtaining normalization
Unmanned plane LiDAR point cloud data;The unmanned plane LiDAR point cloud effect data is shown in Fig. 1.
Canopy structure characteristic variable is extracted, and three groups of characteristic variables, i.e. percentile altitude feature variable, each layer coverage are extracted
Characteristic variable and canopy volume and profile features variable.
Percentile altitude feature variable includes: canopy height distribution percentile (H25, H50, H75, H95), canopy point cloud
It is distributed the coverage (CCmean) of average height or more, the coefficient of variation (Hcv) of canopy point cloud distribution;
Each layer coverage characteristic variable include: cloud quantity each percentage height (30th, 50th, 70th, 90th, i.e.,
D3, D5, D7, D9) more than point account for the percentage of all the points cloud;
Canopy volume and profile features variable include: that Weibull function is fitted to obtain 2 to canopy height profile
A profile features amount α, β (i.e. Weibull α and Weibull β);Each structured sort volume accounting of canopy, including open tier, light transmission
Layer, four canopy structure classifications of low photosphere and confining bed, each canopy structure classification volume percentage (i.e. OpenGap,
Oligophotic, Euphotic, ClosedGap).
Standing forest biophysical properties and unmanned plane LiDAR point cloud feature construction random forest mould are surveyed based on existing ground
Type.M variable is randomly generated for the binary tree on node in mtry value specified first, mtry value is the point cloud for modeling
Feature quantity is 16;Secondly, randomly selecting k sample set using bootstrap method with putting back to, k decision tree is formed,
In, k 1000;It is predicted finally, treating sample according to the random forest that k decision tree forms.
This method uses leave one cross validation, the coefficient of determination (R2), root-mean-square error (RMSE), opposite root-mean-square error
(rRMSE) effect of evaluation model fitting and estimation precision:
X in formulaiFor certain standing forest biophysical properties measured value;Average value is surveyed for certain standing forest biophysical properties;For
The model estimated value of certain standing forest biophysical properties;N for sample ground quantity;I is for some sample.The Random Forest model middle forest
Decomposing biological physical characteristic estimation cross validation results see the table below 2,
Table 2 predicts cross validation results summary sheet based on each standing forest biophysical properties of Random Forest model
And three typical samples unmanned plane LiDAR point cloud atlas see Fig. 1 and Fig. 2, the difference based on Random Forest model prediction
The characteristic variable importance of standing forest biophysical properties is shown in Fig. 3.
Laser radar (LiDAR) technology is to body surface and to analyze one kind of its return signal by transmitting laser pulse
Active remote sensing technology.The information such as high-precision Forest Canopy structure and hayashishita landform can be obtained by LiDAR.Based on unmanned aerial vehicle platform
LiDAR with more flight cost it is low, data acquisition convenient and efficient can obtain the advantages such as high density point cloud, it will help improve
The inversion accuracy of artificial forest biophysical properties, and effectively inhibit the biophysics of forest cover degree height, the high standing forest of biomass special
Property inverting " saturation " problem.
Previous LiDAR is all based on someone's machine platform, and the LiDAR point cloud density of acquisition is all very low, and the feature extracted
Types of variables is less, and this method can obtain highdensity LiDAR point cloud data based on unmanned aerial vehicle platform, and in depth mention comprehensively
The unmanned plane LiDAR point cloud feature of the artificial storey of multiple groups is taken, finally, going inverting standing forest raw using Random Forest model method
Object physical characteristic enhances the ability and precision of inverting.
By the data comparison of table 2 and table 1, verification result shows through the invention to Plain ginkgo artificial forest biology object
Reason characteristic extracts compared with using other close remote sensing techniques to carry out the inverting of standing forest biophysical properties, opposite root mean square
Error reduces 5% or more, and inversion accuracy significantly improves.
Random forest in the present invention is a kind of prediction model, and the model is more superior than traditional Gradual regression analysis model,
Being embodied in it is a kind of machine learning method, belongs to non-parametric model, and usual precision of prediction is higher;And it is pre- by prediction model
The physical characteristic for surveying woods biology then belongs to a kind of existing technology, but the spy that the application is extracted by unmanned plane LiDAR data
It levies variable and ground measured data constructs random forest, and predict artificial forest biophysical properties based on the random forest of building
Will have very big advantage compared with traditional technology.
Specific embodiment is a preferred embodiment of the present invention, is not for limiting implementation and power of the invention
Sharp claimed range, the equivalence changes and modification that content described in all ranges of patent protection according to the present invention is made should all
It is included in the scope of the patent application of the present invention.