CN101839732B - Vegetation structure parameter measurement device based on wireless sensor network - Google Patents

Abstract

The invention relates to a vegetation structure parameter measurement device based on a wireless sensor network. The device is formed by the wireless sensor network and a data processing and node control system, wherein the wireless sensor network is formed by measurement nodes distributed at the upper part and the lower part of the canopy of a study area and routing nodes, and the data processing and node control system is formed by a convergent node and a control terminal remote server in a connecting way; the measurement nodes obtain vegetation parameter information through acquiring the solar radiation of the upper part and the lower part of the canopy at different solar altitudes in one day, and conducts data transmission and positioning through a wireless ad hoc network; the convergent node can upload the data of the measurement nodes to a control terminal through serial ports and GPRS, and vegetation structure parameters are computed through a data processing system; and the control terminal sends commands to the nodes through the convergent node to modify parameter setting. The invention has the advantages that the volume is small, the power consumption is low, the deployment is convenient and the cost is low, the device is suitable for large-area and long-period vegetation parameter measurement, and the practical value and the application prospect are wide in agriculture, ecology and the wireless sensor network technical field.

Description

A kind of vegetation canopy structure parameter measuring apparatus based on wireless sensor network

(1) technical field

The present invention relates to a kind of vegetation canopy structure parameter measuring apparatus based on wireless sensor network, it is relevant with the data acquisition of vegetation canopy structure parameter, belongs to agricultural and ecology and wireless sensor network technology field.

(2) technical background

Vegetation canopy structure parameter is an important indicator of research vegetation growth developmental condition, also is an important relevant parameter of restriction land-atmospheric action process model.Therefore, accurately obtaining vegetation structure parameter is the active demand that promotes land surface model modeling and modelling verification.

Vegetation structure parameter described in the present invention is meant vegetation canopy leaf area index, and (Leaf Area Index is LAI) with leaf inclination angle probability density function.

The acquisition methods of vegetation structure parameter has direct measurement method and indirect measurement method, and wherein direct method comprises that destructive mensuration and manual original position measure and the fallen leaves method.Directly the measurement result precision is high, can be used as the comparison reference of indirect measurement method ratio of precision.But the time-consuming consumption power of measuring process and can cause certain destruction to measuring appearance ground, the numerical value that is difficult to use in the long-time sequence of large tracts of land obtains.

In the indirect surveying instrument to vegetation structure parameter, be through measuring vegetation canopy direction clearance rate, estimating these structural parameters according to the relation of clearance rate and leaf area index and leaf tilt profiles.The difference of these instruments is to obtain the method difference of clearance rate.Can have two types to the commercialization instrument that vegetation structure parameter is measured indirectly at present, first kind is to estimate the canopy transmitance through measuring the solar radiation quantity that sees through in the canopy, like the SunScan and the Australian Demon of Britain.Wherein SunScan is that 64 optical sensors come the disposable multi-level information of obtaining canopy structure information through dispose nearly in canopy bottom, and Demon moves along certain direction or track in the canopy bottom and reaches the purpose of once obtaining multi-angle information through driving (hand-held moving or motor driven) sensor.A kind of in addition is to utilize the hemisphere imaging technique to obtain vegetation and background information in the visual field; Method statistic pixel count separately through classification calculates the direction clearance rate in the canopy; LAI2000 and patent " light transmission layered density determination method and camera " (patent No. 01128255.X) and " a kind of device that is used to measure light transmission layered density " (patent No. 01250965.5) like the U.S.; In order to obtain vegetation canopy multi-angle image, they have adopted the fish eye lens of wide visual field angle to obtain canopy structure information.

The common feature of above surveying instrument is to realize the measurement to the canopy structure parameter through the form that the one-shot measurement in canopy bottom obtains multi-angle canopy radiation profiles information.When in long-time sequence and large space scope, carrying out data acquisition; Because need be at the bigger a plurality of surveying instruments of experiment place deploy; And need personnel repeatedly to measure to the scene; Therefore, more than under instrument and method need expend huge data acquisition cost, comprise human cost and Instrument purchase cost.

Patent of invention " a kind of data collector of trees Canopy Analyzer " (publication number: CN101413875A) pass through at long 1.2-1.8m; The plane deploy of wide 0.6-1.0m nearly 14000 silicon light-sensitive cells or the some coupling element solar radiation of obtaining the trees sylvan life distributes, through the sun in a day move and the variation of solar radiation comes the canopy structure parameter of estimation trees indirectly.Its service condition of the said device of this patent is subject under the environment of forest land, and requires to have under the forest land bigger gap can place this equipment.And in short vegetation or continuous distribution vegetation, like crops, the meadow environment is next can't use.

(3) summary of the invention

1, purpose: to the problem of above equipment with the technology existence; The objective of the invention is a kind of vegetation canopy structure parameter measuring apparatus based on wireless sensor network; This device has that volume is little, cost is low, data are obtained automatically and the characteristics of wireless transmission, can realize under the unmanned situation for a long time, on a large scale, the automatic measurement and the transmission of many vegetation pattern canopy structure parameter.

2, technical scheme: for realizing above-mentioned advantage, the present invention takes following technical scheme:

A kind of vegetation canopy structure parameter measuring apparatus based on wireless sensor network comprises:

By on the canopy that is distributed in study area with canopy under the wireless sensor network formed of measured node and routing node;

The data processing and the node control system that are connected to form by aggregation node and control terminal and remote server.

Wireless sensor network with the position annexation between data processing and the node control system is: wireless sensor network is through installing serial port module additional on its aggregation node, is connected through the RS232 Serial Port Line is in-plant with the node control system with data processing on the control terminal; Wireless sensor network is through installing the GPRS module additional on its aggregation node, be connected at a distance through the GPRS radio communication with the node control system with data processing on being positioned over breadboard remote server.

Wherein, said measured node by be used to measure canopy up and down the sun see through radiation optical sensor, be used for the ephemeral data storage data storage cell, be used to provide the real-time clock of acquisition time, acp chip and the power supply unit that is used to carry out wireless communication network and node control computing to form.Position annexation between them is: optical memory, real-time clock passes through I ²C is connected with acp chip, and data storage cell is connected with acp chip through SPI, and all unit all are connected with power supply unit.All components and parts are distributed in 10 * 4.5cm ²The node circuit plate on.

Wherein, said optical sensor is one 3 * 3mm ²Photoelectric commutator, employing be environment light sensor TSL2561 chip; Said data storage cell is to select M25P10 for use, the storer of 1Mbit; Said real-time clock is to select the timing of PCF8563 chip for use; Said acp chip is the high-power JN5139-Z01-M02R1 module that JENNIC company provides, and it has wireless communication network and Single-chip Controlling operation function simultaneously; Said power supply unit is relevant with the position that node is disposed; Being deployed in node power under the canopy is two joint AA alkaline batteries, is deployed in node and routing node and aggregation node power supply on the canopy and is the combination that solar panel and subsequent use two saves the AA alkaline batteries.

Said routing node is the same on hardware is formed with measured node, and the wireless communication protocol stack that just on driver, calls is different, and routing node can be realized the routing function of signal relay.

One aggregation node is set is used for gathering data, and the data transmission that will gather is given control terminal and remote server from all measured node.

Wherein, Said aggregation node is on the components and parts basis of measured node, to increase a GPRS wireless communication module and serial communication modular; The radio modem that is based on mobile 2.5G Hz GPRS network platform built-in Siemens MC35I/MC39I technical grade module that this GPRS module is selected for use; Can be directly be connected, realize the GPRS data communication with host computer equipment such as industrial computer; It is good that serial communication modular selects for use JENNIC to support, the level conversion chip SP3232 of low-power consumption; Being connected with remote server by aggregation node and control terminal, to form control device be data processing and node control system, transmits spatial positional information and data, and realize wireless telecommunications between the wireless sensor network; Said control terminal and remote server are Net-connected computer.Wherein, Said measured node, routing node and aggregation node have all write the driver of autonomous establishment; The driver structural representation is seen Fig. 1. behind the power switch of opened nodes, at first carry out the initialization of each functional module, routing node can be set up wireless sensor network with other routing nodes and aggregation node through the mode of multi-hop ad hoc at once; In running order always then, wait for the access of measured node at any time.Measured node can be searched the wireless network of being made up of routing node, and behind the access network, measured node gets into duty, according to pre-set time interval, gathers the storage data, and data are sent via wireless network.One time image data finishes, and gets into dormant state, and wait is next constantly restarts interruption, so moves in circles.After a phase data collecting work is accomplished, can interrupt above-mentioned circulation at the timing node of setting, measured node gets into long-time dormant state, waits for collecting work next time.

Wherein, In the said measured node; Be positioned at that the sun sees through radiation under the canopy that measured node under the canopy is used for obtaining one day different sun altitude; Be arranged in the total solar radiation that the measured node on the canopy is used for obtaining one day different sun altitude of study area, measure numerical value from above two and can extract vegetation canopy structure parameter information.

Wherein, Between the said measured node; Between measured node and the routing node; Between routing node and the aggregation node, and aggregation node with the annexation of control terminal and remote server is: the measured node under the measured node on a plurality of (N＜=16) canopy and the canopy links to each other with routing node through the mode of radio communication; Between the routing node, and routing node is connected with the mode of aggregation node through wireless multi-hop ad hoc; Aggregation node also belongs to a routing node in itself, and still, difference is that aggregation node has serial communication modular and GPRS module with common routing node part.Aggregation node links to each other with control terminal or remote server with the GPRS wireless communication module through serial ports.

Wherein, Between said measured node and the routing node; Between routing node and the aggregation node; And the position of aggregation node and control terminal and remote server relation is: measured node will have a routing node as the signal relay point in the measured zone stochastic distribution near per 16 measured node at least, and maximum distance is no more than 200m between measured node and the routing node; Routing node adopts the mode of wireless multi-hop to connect, and will have a routing node coupled at least in the 200m scope around arbitrary routing node; Aggregation node can be positioned over around arbitrary routing node in the 200m scope; Aggregation node can use Serial Port Line to realize the closely data transmission of aggregation node and control terminal, also can use the GPRS module realization aggregation node of aggregation node and the remote data transmission of remote server.

Wherein, Said data processing and node control system run on control terminal and remote server; When data from measured node via routing node, aggregation node is ultimately delivered to after control terminal and the remote server; Data processing and node control system can read and analyze data automatically; Therefrom extract the vegetation canopy direction clearance rate under the different sun altitudes of each measured node, the clearance rate that utilization is extracted is finally inversed by the leaf area index and the leaf tilt profiles of this node place vegetation canopy, and result visualization is shown.Simultaneously, operating personnel can send order to measured node through data processing and node control system, change the parameter setting of measured node, thereby reach the control purpose.

3, advantage and effect: compared with prior art; The present invention is through measuring total solar radiation, measuring the sun in the canopy bottom and see through radiation and reach the purpose of calculating the canopy transmitance on canopy top, utilize that the variation of sun altitude realizes that the canopy clearance rate of multi-angle calculates among one day.And then, utilize the multi-angle clearance rate to calculate the structural parameters of canopy.The present invention utilizes the variation of sun altitude to replace the method that traditional fisheye camera once obtains multi-angle image; And; Because the present invention has directly used the planar light sensor; Can directly calculate the canopy clearance rate, need not observed object is carried out to picture, reduce image classification error in the Data Post.The present invention adopts wireless network to carry out data transmission, has reduced the data storage capacity of single-chip microcomputer, more helps being implemented in the big zone under the unmanned condition, the vegetation canopy parameter acquiring of long-time sequence.

(4) description of drawings

Fig. 1 is a measured node driver structural representation of the present invention

Fig. 2 is a measured node structural representation of the present invention

Fig. 3 is the open-air synoptic diagram of disposing of the present invention

Fig. 4 obtains the control algolithm structural representation for data of the present invention

Symbol description is following among the figure:

1-measured node 2-routing node 3-aggregation node 4-Net-connected computer 5-Net-connected computer

(5) embodiment

A kind of vegetation canopy structure parameter measuring apparatus based on wireless sensor network of the present invention comprises the wireless sensor network of being made up of measured node that is arranged in survey region canopy upper space and lower space 1 and routing node 2; The data processing and the node control system that form by aggregation node 3 and control terminal and remote server.

Wherein, said measured node 1 by be used to measure canopy up and down the sun see through radiation optical sensor, be used for the ephemeral data storage data storage cell, be used to provide the real-time clock of acquisition time, acp chip and the power supply unit that is used to carry out wireless communication network and node control computing to form.Measured node 1 links to each other with routing node 2 through radio communication.Routing node 2 is identical with measured node 1 on hardware; The protocol stack that just on driver, calls is different; The protocol stack that routing node 2 uses can be realized the relaying to wireless signal; Owing to this characteristics are arranged, can connect and form wireless sensor network through the multi-hop wireless communication mode between the routing node 2.Above-mentioned radio communication connects the Jenie communication protocol of all using JENNIC company to provide.This agreement is identical substantially with the protocol function of Zigbee; It is littler that difference is that the agreement of Jenie takes up room, and consumes energy still less, and its shortcoming is the Mesh network agile that does not have the Zigbee agreement; But fix for relative position; Node can not move at any time, under the little situation of obstacles, selects for use the agreement of Jenie to be more conducive to our network arrangement and network utilisation.Exchange in order to carry out data, an aggregation node 3 is set is used for gathering data, and the data transmission that will gather is given control terminal and remote server from all measured node with the external world.This aggregation node 3 is on routing node 2 bases, to have increased to be used for the serial communication modular and the GPRS module that are connected with control terminal and remote server.

Wherein, optical sensor is one 3 * 3mm ²Photoelectric commutator, employing be environment light sensor TSL2561 chip, this chip has photoelectric converting function, directly passes through I ²C transmits the strong numerical information of light echo.Its concrete parameter is following:

WV 2.7-3.6V

Working temperature-30-70 ℃

Signal low level voltage-0.5-0.8V

Signal high level voltage 2.1-3.6V

Wherein, data storage cell is selected M25P10 for use, and the storer of 1Mbit, JENNIC are pointed out the good support to it in explanation.Its concrete parameter is as follows:

Memory space 1Mbit

WV 2.7-3.6V

Working interface SPI interface

Work maximum frequency 50MHz

Wherein, said acp chip, employing be the high-power JN5139-Z01-M02R1 module that JENNIC company provides, this module has wireless communication network and Single-chip Controlling operation function simultaneously.Its module parameter is described below:

Physical parameter:

Transmission range＞1km

Module apparent size 18 * 41mm

WV 2.7-3.6V

Working frequency range 2.4GHz IEEE802.15.4 is compatible

Quiescent current (having wake-up timer)＜2.8uA

19dBm power, band SMA, uFI antenna connector

Receiving sensitivity :-100dBm

TX electric current:＜120mA

RX electric current:＜45mA

Interface parameters:

Five SPI interfaces

Two UART serial ports

Two programmable Timer timers

The I of two lines ²The C mouth

21 general IO mouths (part and UART are multiplexing)

Four road 12-bit, the ADC of 100ksps

The DAC that two-way is 11

A comparer

Temperature inside and voltage sensor

The processor parameter:

32 RISC CPU of 16MHz

·128KB?FLASH、64KB?ROM、96KB?RAM

Wherein, said real-time clock can provide year for the data of gathering, month, day, the time, dividing, PCF8563 is selected in the timing of second for use, and this chip power-consumption is very low, is applicable to the battery powered mode that we adopt.Its concrete parameter is as follows:

Crystal oscillator is 32.768KHz

WV 1.0-5.5V

Working current 0.25uA

Support I ²C interface

Wherein, it is good that said serial communication modular selects for use JENNIC to support, the level conversion chip SP3232 of low-power consumption, and its concrete property is described below:

Satisfy the EIA/TIA-232-F standard

WV is 3.0-5.5V

Fully loaded minimum data rate: 120Kbps

The low-power consumption shutdown mode of 1uA, receiver (SP3222E) is effective

Can use jointly with RS232, power supply is low to moderate+2.7V

Enhancement mode ESD standard:

± 15kV human body discharge mode

± 15kV IEC1000-4-2 bubble-discharge

± 8kV IEC1000-4-2 contact discharge

Wherein, said GPRS module is selected for use is based on the radio modem that moves 2.5G Hz GPRS network platform built-in Siemens MC35I/MC39I technical grade module, can be directly be connected realization GPRS data communication with host computer equipment such as industrial computer.Its concrete property is described below:

Support EGSM900 and GSM1800 double frequency to support numeral, voice, short message and fax

Electric current is the transfer rate that 3mA supports three kinds of speech encodings when being in sleep state

The authentication of standard agreement, employing GSM Phase2/2+ standard

WV 3.3-5.5V

Frequency range: double frequency GSM900MHz and DCS1800MHz (Phase 2+)

Emissive power: 2W (GSM900MHz Class 4) 1W (DCS1800MHz Class 1)

SIM connected mode: external

Antenna: connect exterior antenna by antenna connector

Temperature range: working temperature :-20-+55 ℃ storage temperature :-30-+85 ℃

Working current loss: call mode: 300mA (representative value .) idle pulley: 3.5mA (maximal value pattern: 100uA (maximal value)

Communication interface: RS232 (the two-way transmission of instruction and data)

Wherein, The composition of power supply unit is relevant with the position that node is disposed; Being deployed in node power under the canopy is two joint AA alkaline batteries, is deployed in node and routing node 2 and aggregation node 3 power supplys on the canopy and is the combination of solar panel and subsequent use two joint AA alkaline batteries.

Wherein, said control terminal and remote server are Net-connected computer 4,5.

One of advantage of the present invention is to be fit to obtain large-area vegetation structure parameter, utilizes multi-hop connection between the routing node 2, can the laying range expansion of measured node be arrived 1km ²Perhaps bigger; The concrete laying of measured node is as shown in Figure 2; At first confirm sampling policy according to the actual conditions of measured zone; Confirm to want to obtain each concrete point position of vegetation structure parameter according to sampling policy, place a measured node in the canopy lower space of each such measurement point position then, be used for measuring in one day that the vegetation canopy sun sees through radiation Q under the different sun altitudes _i(wherein i is the numbering of measured node under the canopy).In order to measure total solar radiation and sky radiation on the canopy; Choose 2 point positions in addition; Canopy upper space in each such measurement point position is placed a measured node; And therein one install shade disk above the node additional, be used for measuring in one day under the different sun altitudes total solar radiation Q on the vegetation canopy respectively ₀With sky radiation D ₀After laying 16 measured node, a routing node 2 need be set, the requirement of laying routing node 2 is that to make 16 measured node drop on these routing node 2 peripheral radiuses be in the circumference of 200m.It is a group node that 16 measured node 1 add a routing node 2, can arrange some group nodes at study area.Group with organize between be connected through routing node 2.After each group node arranges; Select in arbitrary routing node 2 peripheral 200m scopes; An aggregation node 3 is set; It is in the nature a routing node 2 that has installed serial port module and GPRS module additional, and aggregation node 3 is used for gathering the data of each measured node of wireless sensor network, and carries out exchanging of data with the external world.Each node is the power switch on the opened nodes after the arrangement of corresponding position fixes, and node is promptly started working.

Measured node 1 lay good after, the measuring process of one whole does, before The sun came up about 1 hour; When sky had only scattered light, measured node began to measure, and read a numerical value then at regular intervals at interval; Falling to the sun is stopped by surveying work, thereby accomplishes one-shot measurement.Canopy measurement up and down can obtain scattered light transmitance T before utilizing The sun came up _d, utilize in the sun altitude one day passing in time and the variation that takes place, through be distributed on the canopy with canopy down and the measured node of sheltering from heat or light on the canopy just obtained in one day the sun different sun altitude lower canopies under through radiation Q _i(i is canopy lower node numbering), the total solar radiation Q on the canopy ₀With sky radiation D ₀

Suitable measurement environment of the present invention is sunny calm daytime, and weather cloudy or strong wind can make measurement result be full of noise and influence measuring accuracy, is not suitable for carrying out surveying work.Because the measured node under the canopy is used the alkaline battery power supply; Stream time is limited; In order to realize that the study area long time period is measured, simultaneously also in order to improve the quality of measurement data, we have carried out following design; The one, each measured node 1 all has two state model, i.e. mode of operation and park mode.Measured node 1 is carried out data acquisition and is communicated by letter under the mode of operation, and measured node 1 gets into deep sleep under the park mode, and electric quantity consumption drops to minimum point.Measured node 1 gets into park mode once gathering the storage transmission back that finishes at once.Measured node 1 time of in whole measuring period, being in mode of operation only accounts for very little ratio like this, thereby makes and can obtain measuring period prolonging.The 2nd, node when in a measuring period, the weather of cloudy or strong wind having occurred, can make it get into park mode only being fit to carry out surveying work promptly sunny calm daytime in the time period of measuring through sending instruction to measured node 1.

Aggregation node 3 Measuring Time section by day gathers the data from each measured node, and after the instruction of receiving the transmission data, aggregation node 3 can send to control terminal and remote server through serial port module and GPRS module with the data of being stored.

After the data processing of moving on control terminal or the remote server and node control system receive the data of aggregation node; Begin to carry out data processing work, data processing and node control system handle each node data according to flow process shown in Figure 3; Because in the actual measurement process, having many factors impacts measurement result; Cause measurement result some noises to occur, thus need carry out Filtering Processing earlier to measurement data, again because measured node 1 is numerical value of interval acquiring at regular intervals; So, need carry out interpolation processing to measurement data in order to obtain any sun altitude lower canopy sunshine transmitance.After the data pre-service finishes, use following core algorithm to realize inverting to vegetation structure parameter:

Utilize the temporal information of real-time clock log on the measured node 1, can each data acquisition be scaled corresponding sun altitude constantly.Through a threshold value constantly is set, can measurement data be divided into before sunrise data and sunrise data afterwards.

Data before sunrise, the sky radiation D ' that obtains by the measured node of not sheltering from heat or light on the canopy ₀The sky scattering that obtains with measured node under the canopy sees through radiation D ' ₁Form, can calculate the scattering transmitance by formula (1), promptly

$T_d=\frac{{\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="HSA00000066238900021.png"\; state="\{\{state\}\}">D</figure-callout>}}_1^{\&prime;}}{D_0^{\&prime;}}---\left(1\right)$

Data after the sunrise, under the some time points that obtained by the canopy lower node, the canopy sun specific sun altitude under is through radiation Q _i(i is a canopy lower node label), under some time points that node obtains on the canopy, the total solar radiation Q under the specific sun altitude ₀Under the some time points that obtain with the node that shelters from heat or light on the canopy, the sky radiation D under the specific sun altitude ₀Form.Utilize this three amounts, can calculate direct light radiancy on the specific sun altitude lower canopy, promptly

E ₀＝Q ₀-D ₀ (2)

The scattered light transmitance T that obtains according to (1) formula _d, the sun that can calculate under the specific sun altitude lower canopy sees through radiancy

E ₁＝Q _i-D ₀×T _d (3)

Then the direct sunlight transmitance under specific sun altitude (h) can be expressed as

$T_s\left(h\right)=\frac{E_1}{E_0}=\frac{Q_i-D_0\&times;T_d}{Q_0-D_0}---\left(4\right)$

Formula (4) can further be transformed to

$T_s\left(h\right)=\frac{Q_i/Q_0-D_0/Q_0\&times;T_d}{1-D_0/Q_0}=\frac{T_Q-\mathrm{\&eta;}{T}_d}{1-\mathrm{\&eta;}}---\left(5\right)$

T wherein _QExpression built-up radiation transmitance, η is the ratio of skylight in built-up radiation, T _dBe the sky scattering light transmission rate.

The data of utilizing measured node 1 in one day, to record can obtain n sun altitude lower canopy direct sunlight transmitance among a day, through following formula:

$T_s\left(h\right)=e^{-{\&Integral;}_0^{\frac{\mathrm{\&pi;}}{2}}k(\mathrm{\&theta;},h)\mathrm{LAId\&theta;}}---\left(6\right)$

Set up the relation between canopy direct sunlight transmitance and the vegetation structure parameter, wherein

k(θ，h)＝A(θ，h)g(θ) (7)

$A(\mathrm{\&theta;},h)=\left\{\begin{array}{cc}\cos \mathrm{\&theta;}& \mathrm{\&theta;}\&le;h\\ \cos \mathrm{\&theta;}[1+2(\tan {\mathrm{\&theta;}}_0-{\mathrm{\&theta;}}_0)/\mathrm{\&pi;}]& h<\mathrm{\&theta;}<\frac{\mathrm{\&pi;}}{2}\end{array}\right.---\left(8\right)$

Comprehensively (6)～(8), and formula (6) both sides are asked logarithm respectively, can obtain

$P\left(h\right)=-\ln \left(T_s\left(h\right)\right)={\&Integral;}_0^{\frac{\mathrm{\&pi;}}{2}}A(\mathrm{\&theta;},h)g\left(\mathrm{\&theta;}\right)\mathrm{LAId\&theta;}---\left(9\right)$

With the leaf inclination angle theta in the canopy uniformly-spaced be divided into m interval, sunshine transmitance observation data under the canopy of n sun altitude obtaining of utilization under the condition of n＞m, can obtain the least square solution of LAI through the matrix linear operation like this.

Order $r\left(\mathrm{\&theta;}\right)=\frac{\mathrm{DL}}{\mathrm{D\&theta;}}=g\left(\mathrm{\&theta;}\right)\mathrm{LAI}---\left(10\right)$

R (θ) is a vegetation group structure parameter, can represent the leaf tilt profiles, can represent that also leaf area index changes.Thus, formula (9) can be written as

$P\left(h\right)={\&Integral;}_0^{\frac{\mathrm{\&pi;}}{2}}A(\mathrm{\&theta;},h)r\left(\mathrm{\&theta;}\right)\mathrm{d\&theta;}---\left(11\right)$

The leaf inclination angle is existed

Between be divided into M interval, each length of an interval degree is Δ θ, each interval leaf area index is L _i, the r (θ that each is interval _i) mean value do

$r_i=\frac{{\mathrm{LAI}}_i}{\mathrm{\&Delta;\&theta;}}---\left(12\right)$

Write formula (11) as discrete form, then

$P\left(h_j\right)=\underset{i}{\overset{m}{\mathrm{\&Sigma;}}}A({\mathrm{\&theta;}}_i,h_j)L_i---\left(13\right)$

As N observation was arranged in one day, each sun altitude is respectively h _j(j=1,2 ..., N), then formula (13) can be write as matrix form

P＝A×L (14)

P=(P wherein ₁, P ₂..., P _N) ^TBe N observation, A ^T=(A _Ij) _{M * N}, L=(L ₁, L ₂..., L _M) ^T

The least square solution of L is:

L＝(A ^TA) ^-1A ^TP (15)

In finding the solution the process of L, consider the influence of observation noise, for preventing singular value, increase a regularization amount H and parameters optimization λ, then

L＝(A ^TA+λH) ^-1A ^TP (16)

The value principle of H is

(i) H is a square formation

(ii) H master's diagonal element is 1 except that the upper left corner and the lower right corner, all is 2

(iii) adjacent with main diagonal angle element is-1

(iv) all the other elements are 0 in the square formation.

λ is a positive constant, when calculating, can adjust according to precision as a result, until the optimum solution that obtains L.

After LAI finds the solution, can try to achieve leaf tilt profiles function g (θ) according to formula (12) and (14).

The sun that measures of each node under the canopy is seen through radiation Q _i(i is canopy lower node numbering) above-mentioned core algorithm of substitution just obtains laying node leaf area index and leaf tilt profiles one to one down with canopy.Utilize each measured node 1 and aggregation node 3 relative position spatially,, just can calculate the absolute spatial position of each measured node, have the inversion result visualization display of spatial information the most at last in conjunction with the spatial orientation information of aggregation node 3.All nodes all can carry out the initialization setting before laying; Comprise the mode of operation time point, the park mode time interval, and wireless self-networking time period; Survey crew can as shown in Figure 3ly utilize data processing and node control system; To aggregation node 3 transmitting control commands, order is issued to the initial setting up that each node is revised node through control terminal or remote server, makes it satisfy measurement requirement through wireless sensor network.

Claims (9)

1. vegetation canopy structure parameter measuring apparatus based on wireless sensor network is characterized in that: it comprise by on the canopy that is distributed in study area with canopy under the wireless sensor network formed of measured node and routing node; The data processing and the node control system that are connected to form by aggregation node and control terminal and remote server;

Wireless sensor network with the position annexation between data processing and the node control system is: wireless sensor network is through installing serial port module additional on aggregation node, is connected through the RS232 Serial Port Line is in-plant with the node control system with data processing on the control terminal; Wireless sensor network is through installing the GPRS module additional on aggregation node, be connected at a distance through the GPRS radio communication with the node control system with data processing on being positioned over breadboard remote server;

Said measured node by the optical sensor that is used to measure the total solar radiation on the canopy be used to measure optical sensor that sun canopy under sees through radiation, be used for data storage cell, the real-time clock that is used to provide acquisition time that ephemeral data stores, the acp chip and the power supply unit that are used to carry out wireless communication network and node control computing form; Position annexation between them is: optical sensor, real-time clock passes through I ²C is connected with acp chip, and data storage cell is connected with acp chip through SPI, and all unit all are connected with power supply unit; All components and parts of this measured node are installed on the node circuit plate;

Said routing node is the same with measured node on hardware is formed, and the wireless communication protocol stack that just on driver, calls is different, and routing node is realized the routing function of signal relay;

Said aggregation node is used for gathering the data from all measured node, and the data transmission that will gather is given control terminal and remote server; This aggregation node is on the components and parts basis of measured node, to increase a GPRS wireless communication module and serial communication modular; Being connected with remote server by aggregation node and control terminal, to form control device be data processing and node control system, transmits spatial positional information and data, and realize wireless telecommunications between the wireless sensor network; In the said measured node; The optical sensor that is positioned on the canopy is used for measuring total solar radiation; The optical sensor that is positioned under the canopy is used for measuring the sun through radiation; The numerical value of the node measurement on the numerical value of the node measurement under the canopy and the canopy is done ratio, promptly obtain vegetation canopy beam radia transmitance, therefrom extract vegetation canopy structure parameter information;

Between the said measured node, between measured node and the routing node, between routing node and the aggregation node; And the annexation of aggregation node and control terminal and remote server is: on 16 canopies with canopy under measured node to add a routing node be a group node; Arrange some group nodes at study area, the measured node under the measured node on the canopy and the canopy links to each other with routing node through the mode of radio communication; Between the routing node, and routing node is connected with the mode of aggregation node through wireless multi-hop ad hoc; Aggregation node also belongs to a routing node in itself, has only increased serial communication modular and GPRS module; Aggregation node links to each other with control terminal and remote server with the GPRS wireless communication module through serial ports;

Between said measured node and the routing node; Between routing node and the aggregation node; And the position of aggregation node and control terminal and remote server relation is: measured node is in the measured zone stochastic distribution; A routing node will be arranged at least as the signal relay point near per 16 measured node, maximum distance is no more than 200m between measured node and the routing node; Routing node adopts the mode of wireless multi-hop ad hoc to connect, and will have a routing node coupled at least in the 200m scope around arbitrary routing node; Aggregation node is positioned over around arbitrary routing node in the 200m scope; Aggregation node uses Serial Port Line to realize the short-range data transmission of aggregation node and control terminal, or uses the GPRS module realization aggregation node of aggregation node and the remote data transmission of remote server;

Said data processing and node control system run on control terminal and remote server; When data from measured node via routing node; Aggregation node; Be ultimately delivered to after control terminal and the remote server, data processing and node control system read and analyze data automatically, therefrom extract the vegetation canopy direction clearance rate under the different sun altitudes of each measured node; The clearance rate that utilization is extracted is finally inversed by the leaf area index and the leaf tilt profiles of this node place vegetation canopy, and result visualization is shown; Simultaneously, operating personnel send order through data processing and node control system to measured node, change the parameter setting of measured node, thereby reach the control purpose.

2. a kind of vegetation canopy structure parameter measuring apparatus based on wireless sensor network according to claim 1, it is characterized in that: this optical sensor is one 3 * 3mm ²Photoelectric commutator, its chip model is TSL2561.

3. a kind of vegetation canopy structure parameter measuring apparatus based on wireless sensor network according to claim 1, it is characterized in that: this data storage cell is the M25P10 storer of a capacity 1Mbit.

4. a kind of vegetation canopy structure parameter measuring apparatus based on wireless sensor network according to claim 1, it is characterized in that: this real-time clock is to select the timing of PCF8563 chip for use.

5. a kind of vegetation canopy structure parameter measuring apparatus according to claim 1 based on wireless sensor network; It is characterized in that: the acp chip that this is used to carry out wireless communication network and node control computing is the JN5139-Z01-M02R1 module that JENNIC company provides.

6. a kind of vegetation canopy structure parameter measuring apparatus according to claim 1 based on wireless sensor network; It is characterized in that: the composition of this power supply unit is relevant with the position that each node is disposed; Being deployed in measured node power supply under the canopy is two joint AA alkaline batteries, and the power supply that is deployed in measured node and routing node and aggregation node on the canopy is the combination that solar panel and subsequent use two saves the AA alkaline batteries.

7. a kind of vegetation canopy structure parameter measuring apparatus based on wireless sensor network according to claim 1 is characterized in that: this GPRS module is a radio modem based on mobile 2.5G Hz GPRS network platform built-in Siemens MC35I/MC39I technical grade module.

8. a kind of vegetation canopy structure parameter measuring apparatus based on wireless sensor network according to claim 1, it is characterized in that: this control terminal and remote server are Net-connected computer.

9. a kind of vegetation canopy structure parameter measuring apparatus based on wireless sensor network according to claim 1, it is characterized in that: all components and parts of this measured node are distributed in 10 * 4.5cm ²The node circuit plate on.

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