CN110210142B - Real-time water demand measuring and calculating method for rice in large irrigation areas in south - Google Patents
Real-time water demand measuring and calculating method for rice in large irrigation areas in south Download PDFInfo
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Abstract
The invention discloses a method for measuring and calculating the real-time water demand of rice in a large irrigation area in the south, belonging to the field of efficient utilization and management of agricultural water and soil resources. Constructing a rice real-time water demand estimation model taking net solar radiation amount, crown gas temperature difference and leaf area index as parameters through a field water demand test of the whole growth period of rice; a rice physiological and growth environment acquisition system of a mobile unmanned aerial vehicle in an irrigation area and an information acquisition system of an automatic agricultural meteorological station in the irrigation area respectively acquire real-time rice physiological information and meteorological information; and (3) converting the physiological information of the rice from point to surface by adopting a Thisen polygon method, and further acquiring the water demand information of the rice on the surface of the irrigation water management unit of the irrigation area. The invention can monitor the water demand information of large-area paddy rice in real time, quickly and accurately, and has important significance for improving the informatization and precision water management level of large irrigation areas in south China.
Description
Technical Field
The invention relates to a method suitable for estimating the real-time water demand of rice in a large irrigation area in the south, and belongs to the field of efficient utilization and management of agricultural water and soil resources.
Background
With the continuous development of water conservancy informatization and agriculture refinement, higher requirements are put forward on water consumption management of irrigated areas. The real-time and accurate estimation of the water demand of crops is the basis of water management of an irrigation area, and the decision and regulation of the water management of irrigation are made on the basis, are not only the technical key for realizing real-time, dynamic and accurate water management of the irrigation area, but also the technical difficulty, so that the method becomes the aim pursued by science and technology workers. The water demand of crops is usually estimated by adopting a crop coefficient method, the required information is more, the real-time water demand information of the crops cannot be directly obtained, the result of the real-time water demand information is corrected according to the soil moisture condition, the process is complicated, the realization difficulty is high, and the error is usually more than 20%. The irrigation area water management usually takes the static water demand process as a basis, and the irrigation area water management plan is made according to the static water demand process, so that the irrigation area water management plan is different from the actual crop water demand, blindness and hysteresis exist in irrigation area water management, and an ideal irrigation effect cannot be achieved. Therefore, people adopt a remote sensing method to remotely measure the canopy temperature, combine a microclimate observation method or utilize other data to estimate the water demand information of crops, and the method has good application prospect. The remote sensing method can be divided into traditional high-altitude remote sensing and unmanned aerial vehicle ultra-low altitude remote sensing, numerous remote sensing information is needed for calculating the water demand of crops through high-altitude remote sensing inversion, the cost is high, the resolution is low, actual calibration tests are lacked in various places, the observation period is long, the influence of meteorological factors is easy, therefore, the water demand information of crops in irrigation areas cannot be reflected in time, and the method is limited in practical application.
In recent years, as the application of the unmanned aerial vehicle technology in the field of agricultural engineering is becoming mature, the utilization of the unmanned aerial vehicle technology to obtain irrigation area information with high timeliness and accuracy becomes one of important means for information construction of irrigation areas in China. At present, grain crops in large irrigated areas in south China mainly plant rice, unmanned aerial vehicle ultra-low-altitude remote sensing is flexible in data acquisition, high in spatial resolution and low in acquisition cost, and rice daily water demand information taking a canal as an irrigation unit can be accurately acquired in real time by combining a rice water demand estimation model, so that a reliable basis is provided for 'dynamic water use' management of the irrigated areas, and the requirement of daily water use management of the irrigated areas is met. The unmanned aerial vehicle monitoring range is matched with the first grade of villages on the administrative district, and the water quantity control equipment is generally arranged at the head of a ditch, so that powerful guarantee is provided for quantitative and timed irrigation, and the unmanned aerial vehicle monitoring system is a practical and feasible way for realizing real-time, dynamic and accurate water consumption management in large irrigation areas in the south.
Disclosure of Invention
The invention provides a method for monitoring water demand of rice in a large irrigation area in the south by using an unmanned aerial vehicle remote sensing technology. Through the field rice water demand test, the real-time water demand estimation model is corrected, and the unmanned aerial vehicle agricultural condition acquisition technology is combined to acquire the rice water demand information in the irrigation unit by taking the ditch in real time, so that a scientific basis is provided for water management of an irrigation area. The method can be used for quickly and accurately acquiring the rice water demand information on the irrigation water management unit of the irrigation area in real time, and has important significance for reducing water resource waste of the irrigation area, improving the utilization efficiency of irrigation water resources and promoting informatization and precision of water management of large irrigation areas in south China.
In order to realize the purpose, the technical scheme of the invention is as follows:
a real-time water demand measuring and calculating method for rice in a southern large irrigation area is characterized by comprising the following steps:
1) Water demand test for paddy rice in field
(1) Preparing the devices required by the field rice water demand test, namely a plurality of bottom measuring barrels, sleeves matched with the bottom measuring barrels, a canopy temperature measuring instrument, a high-precision electronic platform scale and a crop canopy analyzer;
(2) the sleeve is buried in a typical field block in an irrigation unit, a bottoming measuring barrel with rice planted is placed in the sleeve, the planting height of the rice in the barrel is consistent with that of the rice in the irrigation unit, and meanwhile, the production management mode is also consistent with that of the rice in the irrigation unit;
(3) taking out the bottom measuring barrel every day, measuring the weight of the barrel by using a high-precision electronic platform scale, putting the measuring barrel back to the original position after weighing, and converting the weight difference of the bottom measuring barrels in two adjacent days into the actual daily water demand of the rice;
(4) the area index of the rice leaves in the corresponding bottom measuring barrel and the canopy temperature information are respectively obtained by utilizing a crop canopy analyzer and a canopy temperature measuring instrument, and the air temperature and the net solar radiation quantity in the corresponding time period are obtained by means of an automatic agricultural meteorological station in an irrigation area.
2) Rice real-time water demand estimation model
(1) Through a field test of a typical field rice in a whole growth period, a rice real-time water demand estimation model taking solar net radiation, a crown gas temperature difference and a leaf area index as parameters is constructed, and the structure of the model is as follows:
ET m ＝(aLAI+b)[cR n -d(T c -T a )+e]；
in the formula: ET m Calculating a real-time water demand model value for the rice; LAI is leaf area index; r is n For the net solar radiation, the unit is [ MJ/(m) 2 ·d)]；T c Is the canopy temperature; t is a Is the air temperature; t is a unit of c -T a The temperature difference of the coronary gas is expressed in unit; a. b, c, d and e are empirical coefficients;
(2) judging whether parameters are adjusted or not by the rice real-time water demand estimation model through error analysis, and judging whether parameters are adjusted according to relative error R E When R is a judgment index E When the water demand is less than or equal to 10 percent, the model is considered to meet the precision requirement and can be used for estimating the water demand in real time; if the precision does not meet the requirement, continuing to perform field rice water demand test and parameter calibration, and modelingAnd correcting until the precision meets the requirement.
3) Unmanned rice information acquisition
(1) Installing an infrared temperature sensor and a crop canopy analyzer on an unmanned aerial vehicle, controlling the unmanned aerial vehicle to uniformly collect grid points on an irrigation unit according to the minimum sampling number by using a flight controller, and calculating the average value of the temperature of the rice canopy and the leaf area index in the irrigation unit by using a Thiessen polygon method;
(2) and substituting the obtained average value of the rice canopy temperature and the leaf area index in the irrigation unit and the solar net radiation obtained by the automatic agricultural meteorological station in the irrigation area into the rice real-time water demand model meeting the precision requirement, and calculating to obtain the rice real-time water demand in the irrigation area.
Further, in the step 1), the number of the bottom-equipped measuring barrels is not less than 4, the bottom-equipped measuring barrels are placed in sleeves, and the sleeves can prevent soil adhesion from affecting weighing; by measuring the bucket weight G of two days before and after i 、G i-1 The daily water demand of the rice is determined by the following formula, wherein the unit is g, the radius r of a measuring barrel with a bottom is cm:
in the formula: rho is the density of water and is generally 1.0g/cm 3 ，；h i-1 The daily water demand of the rice on the i-1 day is in mm.
Further, in the step 2), the solar net radiation acquired by the automatic agricultural meteorological station in the irrigation area, the canopy gas temperature difference and the leaf area index acquired in the step 1) are taken as parameters, and an empirical coefficient in the real-time water demand estimation model of the rice is obtained by combining SPSS statistical software.
Further, in step 2), the error determination formula is:
in the formula: o. o i Mm/d for measured value of water requirement of rice crops; s i Is a model analog value, mm/d;
the mean value of the measured data is mm/d; n is the number of statistical samples; r MSE Root mean square error, mm/d.
Further, in step 3), the formula of the minimum sampling number of the unmanned aerial vehicle is as follows:
n＝λ α,f ×σ 2 /Δ 2 ；
in the formula: n is the required number of samples; lambda [ alpha ] α，f Is a t distribution characteristic value, alpha is a significant level, 5 percent is taken, f is a degree of freedom, f = N-1, N is total capacity, and lambda α，f Can be obtained by looking up a distribution table of t by alpha and f; delta is sampling precision, delta = ku, u is a mean value, and a relative error k is taken as 5%; sigma 2 Is the overall variance;
based on the canopy gas temperature difference and the leaf area index obtained in the step 1), calculating the sampling number n of the canopy temperature and the leaf area index respectively by adopting a minimum sampling number formula 1 、n 2 And the two values are taken as n, and the unmanned aerial vehicle carries out uniform fixed grid setting sampling points on the irrigation unit according to the minimum sampling number n.
Further, GPS positioning on the unmanned aerial vehicle assists in planning a flight path and correcting the flight altitude.
Further, in the step 3), the average value of the rice canopy temperature and the leaf area index in the irrigation unit is described by using a Thiessen polygon method, and the specific method is as follows:
according to the rice canopy temperature, the leaf area index and the GPS positioning information of each sampling point, connecting adjacent sampling points by straight lines to form n-2 triangles, then making a vertical bisector of each side of each triangle, dividing the irrigation unit into n polygons, wherein each polygon contains one sampling point, and the average rice canopy temperature and the leaf area index of the irrigation unit are calculated by taking the polygon area as weight;
the average value formula of the obtained rice canopy temperature is as follows:
the obtained leaf area index average value formula is as follows:
in the formula:
the average value of the temperature of the canopy is unit ℃;
is the mean value of the leaf area index; f is the area of the irrigation unit, and the unit is mu; f. of i The area of the polygon where the ith sampling point is located is the unit of mu; t is ci The temperature information of the canopy at the ith sampling point is shown in unit; LAI i Leaf area index information of the ith sampling point; n is the number of polygons i.
Furthermore, the automatic agricultural meteorological station in irrigated area is located inside typical field of irrigated area, and the mounting height is 1.5m, acquires the clean radiation of sun and the air temperature in the irrigation unit automatically.
Furthermore, the irrigation unit is a ditch, and the control area is about 1500 mu generally; the daily monitoring time interval of the unmanned aerial vehicle is preferably 13-00, the observation can be adjusted if the unmanned aerial vehicle meets rainfall and strong wind, the mobile information collection is stopped all day after rainy days, and the observation is carried out after the rainy days are stopped if the unmanned aerial vehicle meets short-term rainfall weather.
The invention relates to a (square) bottom measuring barrel, a sleeve, an electronic platform scale meeting the precision requirement, a canopy temperature measuring instrument and a handheld crop canopy analyzer, which are used for measuring the actual water-requiring process of rice in the whole growth period and the physiological information of the rice under the condition close to the growth environment in the field. The unmanned aerial vehicle is a multi-rotor unmanned aerial vehicle, and rice canopy temperature and leaf area index information in the large irrigation area ditch irrigation unit are collected regularly and movably. An automatic agricultural meteorological station for irrigated area mainly collects agricultural meteorological information including solar net radiation, average temperature of irrigation unit and the like. The method comprises the steps of constructing a rice real-time water demand estimation model taking net solar radiation amount, canopy gas temperature difference and leaf area index as parameters through field tests of field rice in a whole growth period; the unmanned aerial vehicle collects the physiological and growth environment information of the rice and the meteorological information collected by the automatic agricultural meteorological station in the irrigation area in real time; and (3) converting the physiological information of the rice from point to surface by adopting a Thisen polygon method, and further acquiring the water demand information of the rice on the surface of the irrigation water management unit of the irrigation area. The method can quickly, real-timely and accurately monitor the water demand information of the large-area rice, and has important significance for improving the informatization and accurate water consumption management level of large irrigation areas in south China.
Compared with the existing crop water demand estimation method, the method has the following beneficial effects:
firstly, the rice real-time water demand estimation model grasps key elements of real-time water demand of crops, and combines rice leaf area indexes reflecting actual growth conditions of the crops, and driving factors of canopy temperature difference and solar net radiation influencing real-time water demand characteristics of the crops. Compared with the traditional crop water demand estimation method, the method has the advantages of strong factor representativeness, small quantity, convenient collection and low cost.
Secondly, the rice physiological indexes are acquired through the unmanned aerial vehicle mobile information, and then the rice physiological indexes on the surface are processed by adopting a Thiessen polygon method, so that the spatial variability of the water requirement of crops is fully considered, and the problem that the existing methods cannot effectively solve is solved.
Thirdly, the rice water demand information in the irrigation unit is acquired in real time through the unmanned aerial vehicle, so that the timeliness and the accuracy of irrigation area information acquisition are greatly improved, and beneficial attempts are made for the information development of the irrigation areas.
Drawings
FIG. 1 is a schematic flow chart of a method for measuring and calculating the real-time water demand of rice in a southern large irrigation area according to the invention;
FIG. 2 is a schematic diagram of the method for acquiring physiological indexes of rice by an unmanned aerial vehicle according to the invention;
FIG. 3 is a comparison graph of the measured value and the measured value of the water demand of rice in the field test according to the embodiment of the present invention;
in the figure: 1 many rotor unmanned aerial vehicle, 2 infrared temperature sensor, 3 crop canopy analyzers, 4 flight control wares, 5 preset sampling points, 6 graticule meshes.
Detailed Description
Embodiments of the invention are described in further detail below with reference to the following figures and examples:
as shown in figure 1, the invention provides a real-time water demand measuring and calculating method suitable for a rice area in a large irrigation area in the south, which comprises the following steps:
firstly, at least 4 barrels with bottoms are buried in sleeves of typical fields in the field, the height of rice in the barrels is consistent with that of rice in the field, and meanwhile, the production management mode is also consistent with that of the field. Measuring the weight of the bucket by using an electronic platform scale, and converting the weight difference into the actual daily water demand of the rice; the canopy temperature measuring instrument and the handheld canopy analyzer respectively acquire the rice leaf area index and canopy temperature information in the corresponding measuring barrel; meteorological data is provided by an automated agricultural meteorological station at irrigation areas within a typical field.
The actual rice water demand ET can be known through SPSS analysis a And net solar radiation R n Is positively linearly related to the temperature difference T of the coronary gas c -T a Is a negative linear correlation. Considering that the growth and development conditions of rice plants can also influence the water demand of the rice field, the leaf area index is adopted to correct the water demand estimation model.
Through a field test of a rice growth period, a rice real-time water demand estimation model taking net solar radiation quantity, crown gas temperature difference and leaf area index as parameters is constructed, and the structure of the model is as follows:
ET m ＝(aLAI+b)[cR n -d(T c -T a )+e]。
in the formula: ET m Calculating a real-time water demand model value for the rice; LAI is leaf area index; r n For net solar radiation, [ MJ/(m) 2 ·d)]；T c -T a The temperature difference of the crown gas is DEG C; a. b, c, d and e are empirical coefficients.
Performing regression analysis by using measured data to determine the modelThe value and error analysis index of each parameter include the determination coefficient R 2 Root mean square error R MSE Relative error R E And a consistency index d, as shown in fig. 3. With a relative error R E As a main judgment index, when R E When the water demand is less than or equal to 10 percent, the model can be considered to meet the requirements and can be used for estimating the water demand of crops in real time. And when the model precision does not meet the requirement, repeating the field test until the precision meets the requirement.
Through a field test of a typical field block of a large irrigation area in Jiangsu, SPSS software and the formula are utilized to determine the values of all the parameters: a =0.018, b =0.890, c =0.420, d = -0.318, e =0.866, relative error R E The content was 8.15%.
Then, as shown in fig. 2, 100m × 100m grids are arranged in a range of about 1500 mu controlled by the irrigation unit canal, the number of quasi-sampling is determined according to a minimum sampling quantity formula, the preset sampling points are uniformly distributed on the grids, and the minimum sampling quantity formula is as follows:
n＝λ α,f ×σ 2 /Δ 2 。
in the formula: n is the required number of samples; lambda [ alpha ] α，f For t distribution eigenvalues, α is a significant level, typically 5%, f is the degree of freedom, f = N-1, N is the total capacity, λ α，f Can be obtained by looking up a distribution table of t by alpha and f; Δ is sampling precision, generally, a relative error k is taken as 5% according to Δ = ku and u as a mean value; sigma 2 Is the overall variance.
Respectively adopting the above-mentioned formula to calculate minimum sampling number n of canopy temperature and leaf area index 1 、n 2 The two are taken as the larger value.
The unmanned aerial vehicle information acquisition system carries out uniform grid setting and quasi-sampling points on the irrigation unit according to the minimum sampling number n. The GPS positioning on the unmanned aerial vehicle is used for assisting in planning the air route, and the flight controller 4 records the flight path and corrects the flight height. The unmanned aerial vehicle 1 is provided with an infrared sensor 2 and a crop canopy analyzer 3 to acquire real-time rice physiological information, wherein the real-time rice physiological information comprises canopy temperature and leaf area index information, and the flight time interval of the unmanned aerial vehicle is generally 13-00: 00. if special weather conditions such as rainfall, strong wind and the like are met, the mobile information acquisition is stopped when the rain is rainy all day, and if the rain is rainy for a short time, the mobile information acquisition is stopped after the rain is stopped.
According to the rice canopy temperature, the leaf area index and the GPS positioning information of each sampling point, adjacent sampling points are connected by straight lines to form n-2 triangles (generally acute triangles), then perpendicular bisectors of each side of each triangle are made, the irrigation unit is divided into n polygons, each polygon contains one sampling point, and the average rice canopy temperature and the leaf area index of the irrigation unit are calculated by taking the polygon area as a weight. The concrete formula is as follows:
in the formula:
the average value of the temperature of the canopy is DEG C;
is the mean value of the leaf area index; f is the irrigation unit area, mu; f. of i The area of the polygon where the ith sampling point is located is mu; t is ci The canopy temperature information of the ith sampling point is in DEG C; LAI i Leaf area index information of the ith sampling point; n is the number of polygons i.
Agricultural weather information such as average solar net radiant quantity and air temperature in the irrigation unit is acquired through an automatic agricultural weather survey station of an irrigation area installed in a typical field.
And finally, inputting the calculated real-time canopy temperature and leaf area index information of the rice and the collected meteorological information into a water demand model to obtain the real-time rice water demand information of the irrigation unit.
In conclusion, the method can accurately, quickly and real-timely obtain the water demand information of the rice on the surface, and has important significance for improving the informatization and precision water management level of large irrigation areas in south China and reducing the waste of water resources.
Claims (7)
1. A real-time water demand measuring and calculating method for rice in a southern large irrigation area is characterized by comprising the following steps:
1) Water demand test for paddy rice in field
(1) Preparing the required tools for the field rice water demand test, namely a plurality of bottom measuring barrels, sleeves matched with the bottom measuring barrels, a canopy temperature measuring instrument, a high-precision electronic platform scale and a crop canopy analyzer;
(2) the sleeve is buried in a typical field block in an irrigation unit, a bottoming measuring barrel with rice planted is placed in the sleeve, the planting height of the rice in the barrel is consistent with that of the rice in the irrigation unit, and meanwhile, the production management mode is also consistent with that of the rice in the irrigation unit;
(3) taking out the bottom measuring barrel every day, measuring the weight of the barrel by using a high-precision electronic platform scale, putting the measuring barrel back to the original position after weighing, and converting the weight difference of the bottom measuring barrels in two adjacent days into the actual daily water demand of the rice;
(4) utilizing a crop canopy analyzer and a canopy temperature measuring instrument to respectively obtain the rice leaf area index and canopy temperature information in a corresponding bottom measuring barrel, and obtaining the air temperature and the net solar radiation quantity in a corresponding time period by means of an automatic agricultural meteorological measuring station in an irrigation area;
2) Rice real-time water demand estimation model
(1) Through a field test of a typical field rice in a whole growth period, a rice real-time water demand estimation model taking solar net radiation, a crown gas temperature difference and a leaf area index as parameters is constructed, and the structure of the model is as follows:
ET m ＝(aLAI+b)[cR n -d(T c -T a )+e]；
in the formula: ET m Calculating a real-time water demand model value for the rice; LAI is leaf area index; r is n For net solar radiation, the unit is [ MJ/(m) 2 ·d)]；T c Is the canopy temperature; t is a Is the air temperature; t is a unit of c -T a The temperature difference of the coronary artery gas is expressed in unit; a. b, c, d and e are empirical coefficients;
(2) judging whether parameters are adjusted or not by the rice real-time water demand estimation model through error analysis, and judging whether parameters are adjusted according to relative error R E When R is a judgment index E When the water demand is less than or equal to 10 percent, the model is considered to meet the precision requirement and can be used for estimating the water demand in real time; if the precision does not meet the requirement, continuing to perform field rice water demand tests and parameter calibration, and correcting the model until the precision meets the requirement;
3) Unmanned rice information acquisition
(1) Installing an infrared temperature sensor and a crop canopy analyzer on an unmanned aerial vehicle, controlling the unmanned aerial vehicle to uniformly collect grid points on an irrigation unit according to the minimum sampling number by using a flight controller, and calculating the average value of the rice canopy temperature and the leaf area index in the irrigation unit by using a Thiessen polygon method;
(2) substituting the obtained average value of the rice canopy temperature and the leaf area index in the irrigation unit and the solar net radiation obtained by the automatic agricultural meteorological station in the irrigation area into a rice real-time water demand model meeting the precision requirement, and calculating to obtain the real-time water demand of the rice in the irrigation area;
in step 3), the formula of the minimum sampling number of the unmanned aerial vehicle is as follows:
n＝λ α,f ×σ 2 /Δ 2 ；
in the formula: n is the required number of samples; lambda [ alpha ] α，f Is a t distribution characteristic value, alpha is a significant level, 5 percent is taken, f is a degree of freedom, f = N-1, N is total capacity, and lambda α，f Can be obtained by looking up a distribution table of t by alpha and f; delta is sampling precision, delta = ku, u is a mean value, and a relative error k is taken as 5%; sigma 2 Is the overall variance;
based on the crown gas temperature difference and the leaf area index obtained in the step 1), respectively calculating the sampling number n of the crown layer temperature and the leaf area index by adopting a minimum sampling number formula 1 、n 2 Taking a larger value of the two as n, and uniformly setting sampling points on the irrigation unit by the unmanned aerial vehicle according to the minimum sampling number n;
in the step 3), the average value of the rice canopy temperature and the leaf area index in the irrigation unit is described by using a Thiessen polygon method, and the specific method comprises the following steps:
according to the rice canopy temperature, the leaf area index and the GPS positioning information of each sampling point, connecting adjacent sampling points by straight lines to form n-2 triangles, then making a vertical bisector of each side of each triangle, dividing the irrigation unit into n polygons, wherein each polygon contains one sampling point, and the average rice canopy temperature and the leaf area index of the irrigation unit are calculated by taking the polygon area as weight;
the average value formula of the obtained rice canopy temperature is as follows:
the obtained leaf area index average value formula is as follows:
in the formula:
the average value of the temperature of the canopy is unit ℃;
is the mean value of the leaf area index; f is the area of the irrigation unit, and the unit is mu; f. of i The area of the polygon where the ith sampling point is located is the unit of mu; t is ci The temperature information of the canopy at the ith sampling point is shown in unit; LAI i Leaf area index information of the ith sampling point; n is the number of polygons i.
2. The method for measuring and calculating the real-time water demand of the rice in the southern large irrigation area according to claim 1, wherein in the step 1), the number of the bottom-equipped measuring barrels is not less than 4, the bottom-equipped measuring barrels are placed in sleeves, and the sleeves can prevent soil adhesion from influencing weighing; by measuring the bucket weight G of two days before and after i 、G i-1 In units of g, half of a bottomed measuring barrelThe diameter r is in cm, and the daily water demand of the rice is determined by the following formula:
in the formula: rho is the density of water and is 1.0g/cm 3 ；h i-1 The daily water demand of the rice on the i-1 day is in mm.
3. The method for measuring and calculating the real-time water demand of rice in the large irrigation area in the south of claim 1, wherein in the step 2), the solar net radiation acquired by an automatic agricultural meteorological station in the irrigation area and the canopy air temperature difference and the leaf area index acquired in the step 1) are taken as parameters, and an empirical coefficient in a rice real-time water demand estimation model is obtained by combining SPSS statistical software.
4. The method for measuring and calculating the real-time water demand of the rice in the southern large irrigation area as claimed in claim 1, wherein in the step 2), the error judgment formula is as follows:
in the formula: o. o i Mm/d is the actual measured water requirement of the rice crop; s is i Is a model analog value, mm/d;
the mean value of the measured data is mm/d; n is the number of statistical samples; r is MSE Root mean square error, mm/d.
5. The method for measuring and calculating the real-time water demand of the rice in the southern large irrigation area as claimed in claim 1, wherein a GPS (global positioning system) on an unmanned aerial vehicle assists in planning a flight path and correcting the flight height.
6. The method for real-time water demand measurement and calculation of rice in a large irrigation area in the south of claim 1, wherein the automatic agricultural meteorological station in the irrigation area is located inside a typical field, is installed at a height of 1.5m, and automatically obtains the solar net radiation and the air temperature in an irrigation unit.
7. The method for measuring and calculating the real-time water demand of the rice in the large southern irrigation area according to claim 1, wherein the irrigation unit is a canal, and the control area is 1500 mu; the daily monitoring time interval of the unmanned aerial vehicle is preferably 13-00.
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