CN105352979B - Soil moisture method of estimation based on Big Dipper GEO satellite signal - Google Patents
Soil moisture method of estimation based on Big Dipper GEO satellite signal Download PDFInfo
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Abstract
The present invention relates to a kind of soil moisture method of estimation based on Big Dipper GEO satellite signal, is a kind of method for carrying out soil moisture retrieval using Big Dipper GEO satellite direct signal and reflected signal signal-to-noise ratio data.It is of the invention mainly to estimate soil moisture value using the variance of the reflectance factor of Beidou receiver reception GEO satellite signal；Draw actual measurement soil moisture variation tendency and variance variation tendency comparison diagram, compare both correlations, it is computed its coefficient correlation and can reach 0.71, finally it is fitted variance and surveys the relation between soil moisture, using fit come logarithmic relationship model, with reference to certain day Big Dipper Signal-to-Noise data come estimate the same day soil moisture.The present invention has expanded the application field of Big Dipper signal, can apply to agricultural irrigation and meteorological aspect is studied.
Description
Technical field
The present invention relates to electronics, areas of information technology, are a kind of soil moisture estimation sides based on Big Dipper GEO satellite signal
Method, and in particular to a kind of to carry out soil moisture using the variance of Big Dipper GEO satellite direct signal and reflected signal signal-to-noise ratio data
The method of estimation.
Technical background
Soil moisture plays an important role in meteorology, the hydrology, agricultural environment research.The measurement of soil moisture data, it is right
The forecast of the weathers such as potential flood, arid can provide information.Soil moisture data is reduced to the Rational Irrigation of crop
Water resource waste, reduces production cost and raising crop yield is also extremely important.
In the inversion method of current soil moisture, the comparative maturity of development has following in site measurement method, such as weight
Mensuration, tensometer method, electric-resistivity method, Neutron probe method etc..
In the last few years, it has been found that satellite-borne microwave remote sensing can be used for large area monitoring soil moisture (Zhang Xiaojuan, Zhang Wen
Lucky Dual-Frequency Synthetic Aperture Radar for Deep Soil Moisture Estimation CAS Electronics Research Institute Beijing .2007), spaceborne optics is distant
Sense and a kind of means.But space remote sensing means, such as the method for SAR radar inverting humidity are utilized to be limited to returning to for satellite
In the cycle, same place is only passed through, so it can not be obtained in the specific period into periodic rotary around Earth's orbit due to satellite
Obtain a certain place round-the-clock data.
In addition, it is also a kind of exploration using GPS or GNSS-R satellite-signal remote sensing humidity.A kind of method is done using GPS
Signal is related to, soil moisture retrieval (patent CN201010207399.2) is realized for example with the flex point of search interference signal.Separately
A kind of method is that the ratio that reflected signal and direct signal were carried out using antenna and receiver is studied come Soil Moisture (sternly
Hua Zhangxun tools are praised, the soil moisture retrieval research based on GNSS-R signals, electric wave science journal, the 1st phase in 2010).But this
A little researchs are all directed to gps satellite, due to the global motion of gps satellite, the not work in which fixed location year in year out, institute
Even if to employ reflectance factor to study, also due to the elevation bearing angle of satellite is indefinite, and a kind of high elevation angle can only be used near
As method calculate, lack accuracy.
Dipper system formally puts into operation, the dipper system spacing wave published according to China in the end of the year 2013
ICD discloses service signal 2.0 editions, and dipper system discloses service performance specification, and the current operation on orbit of system is defended
Star has 5 geostationary orbit satellite (GEO) satellites, and 5 tilt height in geo-synchronous orbit satellite (IGSO) satellite and 4
Circular orbit satellite (MEO) satellite, formally serves Asia-Pacific region, there is provided horizontal and vertical positioning precision is better than 10m (confidences
The service range of degree 95%), i.e. dipper system disclose service area.
This invention particularly focuses on the geostationary orbit satellite GEO in big-dipper satellite constellation, (numbering is C01 C02 C03
C04 C05), it has fixed elevation, trapped orbit height, and according to the characteristics of big-dipper satellite, the satellite is whole day 24 hours not
The offer of interruption accurately navigation signal, and because its relative position of the earth is fixed, therefore, in the situation that receiver location is fixed
Under, the signal-to-noise ratio data at same place any moment can be obtained；In addition, immobilized just because of its overlay area, therefore
The variance characteristic of its reflected signal reflects the trend of soil moisture, can be used for estimating soil moisture, while be also beneficial to this hair
It is bright to carry out actual humidity measurement using in the overlay area, to establish the functional relation with variance.
The content of the invention
The problem of existing for background technology, the present invention propose the variance characteristic of the reflectance factor using Big Dipper GEO satellite
To estimate the method for soil moisture.The function established reflectance factor variance and survey humidity is returned by long-term observation data
Relation, finally estimate soil moisture using the relation.
The present invention uses the ratio between signal to noise ratio of direct signal and reflected signal --- the side of reflectance factor in Big Dipper GEO satellite
Poor characteristic estimates soil moisture.Due to reflectance factor variance change with soil moisture change presentation is certain associates, can be with
Using the variance counted logarithmic relationship corresponding with soil moisture, establish using variance to estimate the mathematics of soil moisture
Model.In estimation afterwards, it is possible to using the functional relation, by known direct signal and the signal to noise ratio number of reflected signal
According to trying to achieve reflectance factor, and then be estimated that soil moisture at that time.
The technical scheme is that a right-handed polarized antenna upward and a left-hand polarized antenna directed downwardly are set
(being respectively intended to receive direct signal and reflected signal), two Beidou receivers, and the GPRS of the band SIM certifications of transmission signal
Transmission card, PC is transferred data to, lay humidity sensor in situ on the spot in early stage, data are analyzed.Afterwards can be with
Remove hygrometer in situ.
A kind of soil moisture method of estimation based on Big Dipper GEO satellite signal, it is more obvious first to obtain soil moisture change
The direct signal of nearly 2 months (nearly 2 months at the beginning of 12 months from mid-September) and the signal-to-noise ratio data of reflected signal,
The ratio for obtaining reflected signal and direct signal again is worth to reflectance factor, and variance is asked for it, compares variance and true humidity
Correlation, finally variance and humidity are carried out curve fitting, establish contacting for variance and soil moisture, finally closed according to the function
System, the humidity value on the same day is estimated by certain day Big Dipper GEO satellite Signal-to-Noise data.
Specifically include following steps；
Step 1, overlay area determination and raw data acquisition：
Overlay area is determined according to the position and height of the elevation bearing angle of Big Dipper GEO satellite and reception antenna.
GEO satellite direct signal is received using right-handed polarized antenna, left-hand polarized antenna receives GEO reflected signals.Lead to again
Cross CPU DTU and receive the signal that two antennas transmit, output signal-to-noise ratio data, data are finally passed into laboratory
On server.
Step 2, data preselect：
Select in Big Dipper GEO satellite direct signal and reflected signal, the data conduct that whole day has signal to noise ratio for 24 hours is treated
The data source of processing.
Step 3, Big Dipper Signal Pretreatment：
UTC time that the GEO satellite signal received is included, the elevation angle, azimuth, signal to noise ratio data in noise
Than being extracted with UTC time information, and respectively by direct signal and the time unifying of reflected signal, then ask for reflectance factor
Value, the reflectance factor now obtained are that per second have data.
Step 4, variance is asked for：
Because data are changes within half an hour, the size of disturbance is measured with variance.Per half an hour is asked for respectively
The variance of 1800 reflectance factors of period reflects the fluctuation situation of reflectance factor.
Step 5, compare the Long-term change trend relation of variance and soil moisture and be fitted both empirical models：
The letter such as the signal to noise ratio of the Big Dipper GEO satellite signal of continuous processing nearly 2 months or so, the elevation angle, azimuth, UTC time
Breath, its actual measurement soil humidity value daily with 2 middle of the month is contrasted, this 2 months variance is sequentially arranged, and
This 2 months soil moisture value is sequentially arranged, finally both are plotted in a figure, passes through nonlinear regression point
Variance change and the logarithmic function relation of soil moisture change are established in analysis.
Step 6, soil moisture is estimated using logarithmic function relation：
After the big-dipper satellite signal-to-noise ratio data for obtaining certain day certain period half an hour, the half an hour is obtained by data processing
The variance yields of period, the soil moisture of the period can be obtained by substituting into logarithmic function relation.
Brief description of the drawings
Fig. 1 is the Big Dipper GEO signal receiving antenna schematic diagrames that the present invention is implemented；
Fig. 2 is coverage diagram of 5 GEO satellites of the Big Dipper when reception antenna is high 2 meters；
Fig. 3 is that the Big Dipper direct signal that the present invention is implemented preselects with reflected signal signal-to-noise ratio data；
Fig. 4 is the Big Dipper signal reflex coefficient figure that the present invention is implemented；
Fig. 5 is the Big Dipper signal-data processing flow chart that the present invention is implemented；
Fig. 6 is the variance and actual measurement soil moisture variation tendency comparison diagram that the present invention is implemented；
Fig. 7 is the logarithmic function graph of a relation of Big Dipper satellite signal variance and actual measurement soil moisture that the present invention is implemented.
Concrete scheme is implemented
In current research, the method that soil moisture retrieval has pointed out has many, such as interference signal method, bounce technique
Deng.The present invention uses a kind of new approaches, utilizes the fluctuation situation of the reflectance factor of Big Dipper stationary orbit GEO satellite signal --- side
Soil moisture is estimated in the change of difference, the signal-to-noise ratio data obtained by Beidou receiver, calculates the variance of reflectance factor, builds
The mathematical modeling of difference of cubes and soil moisture.Last can calculates the Big Dipper Signal-to-Noise data side of certain period as needed
Difference estimates the soil moisture value of the period.
It is characteristic of the invention that its overlay area is determined according to the orientation of GEO satellite first；The Big Dipper GEO signals of use
Signal-to-noise ratio data, extract the variance of reflectance factor；Establish the functional relation of actual humidity value variance in region；Finally by
Variance estimates soil moisture.
Below with specific embodiment and with reference to accompanying drawing, the invention will be further described.
Step 1：Overlay area determines and raw data acquisition
Fig. 1 devices are for gathering original Big Dipper signal, wherein 1 is GEO No.1 satellite；2 be right-handed polarized antenna, is used
To receive direct signal；3 be left-hand polarized antenna, receives reflected signal；4 be CPU DTU, and day is come from for receiving
The signal of line, output signal-to-noise ratio data, and transfer data on the server in laboratory；The height on antenna distance ground is
2m.Because the present invention is using No. 1 satellite-signal, so its fixed elevation is 43 °.
Fig. 2 is that different when reflection receivable antenna is high 2 meters of 5 GEO satellites (C01, C02C03C04C05) are covered
Cover area.Wherein 5-9 is the area coverage of 5,2,3,1, No. 4 GEO satellites respectively, and its area coverage is 11m respectively2, 3.3m2,
1.8m2, 2.6m2, 5.7m2。
Initial data includes：Big Dipper direct signal signal to noise ratio snrd, reflected signal signal to noise ratio snrr, direct signal UTC time
Td, reflected signal UTC time Tr。
The collection of measured data：(using in Fig. 2 at the overlay area of Big Dipper GEO satellite and reception antenna.Set
Soil moisture observation station, hygrometer is inserted at soil 0-5cm, continuously measure the soil moisture m of 2 months or sovj(i) data,
Wherein, segment labeling when j is represented 48 and a half hours one day, such as from 2014.11.14 0000:00-00:29:59 be the of this day
One and a half hours period, now j value is that 1, j span is 1-48, and i value represents at i-th point of the jth period, i's
Span is 0-1800, thus soil moisture data be each second once, in experiment, actual measurement humidity data is per second to receive one
Secondary, this means that the data volume that the present invention is handled can be very big, but combines actual analysis, and one side humidity data was at one second
Inside have almost no change, on the other hand, power supply that may be local has the factor such as unstable, and these factors cause the precision of data
It is not high, therefore invention defines a kind of special humidity sensor --- medial humidity sensor.This sensor every half is small
When transmission primaries data smn, smnIt is soil moisture value m per secondviPer half an hour average value, calculation formula is as follows：
Data storage contrasts object for actual measurement humidity sequence S as variance.S expression formula is as follows：
Wherein, m rows represent one day m data, and in this experiment, due to being half an hour to receive a data, m value is
48, n row represent total number of days of measurement, and this one data for measuring 2 months of experiment, n value is 60.
Step 2：Data preselect
The Big Dipper signal collected includes UTC time T, the elevation angle, azimuth, signal to noise ratio snr information, extraction wherein No.1
The UTC time T and signal to noise ratio snr of satellitedWith SNRr, be in figure 3 on November 14th, 2014 direct signal signal to noise ratio with reflection
Signal-to-Noise, wherein 10 be direct signal signal to noise ratio, 11 be reflected signal signal to noise ratio, and direct signal signal to noise ratio is greater than reflection
Signal-to-Noise.
Because signal to noise ratio is that have a data each second, thus one day about 86000 points, the signal-to-noise ratio data of selection
It is as far as possible complete, less appearance breakpoint or null value.
Step 3：Big Dipper Signal Pretreatment
First by the UTC time T of direct signal signal to noise ratiodWith the UTC time T of reflected signal signal to noise ratiorAlignment, Ran Houji
Calculate reflectance value, reflectance factor ΓkExpression formula is as follows：
Γk=SNRr(k)/SNRd(k)
Wherein SNRrIt is reflected signal signal to noise ratio, SNRdIt is direct signal signal to noise ratio, Ps is the effective power of signal, and Pn is
The effective power of noise, Vs are the effective voltage of signal, and Vn is root-mean-square noise voltage.The data of kth second during k is represented one day.
Step 4：Step 4 is divided to for two steps, i.e., asks for desired value first, then seek variance.
(1) reflectance factor desired value is asked for
By the reflectance factor per second tried to achieve per half an hour averagely once, one day 48 reflectance data, such as Fig. 3 are obtained
It is shown, reflectance factor desired value ΓaveFormula is as follows：
Wherein, ΓkFor the reflectance value of once per second, had because per half an hour has 1800 seconds, therefore per half an hour
About 1800 data, the Γ asked foraveIt is the variance yields of per period half an hour, shares within one day 48 values.No. 12 lines in Fig. 4
It is the reflectance factor desired value of certain day, it can be seen that average reflection coefficient value changes between 0.6-1, ripple in one day
Dynamic amplitude is little.
(2) variance is asked for
According to the average reflection coefficient desired value Γ of calculatingave, ask for the variance yields D of reflectance factorave, expression formula is as follows：
Wherein, pkFor k-th of reflectance factor ΓiThe probability of appearance, ΓaveFor reflectance factor Γ desired value.
Finally give a variance sequence D, one day 48 value, the data of 2 months altogether.
Step 5：Draw the Long-term change trend relation of variance and soil moisture and be fitted both empirical relations
The continuous processing signal-to-noise ratio data of 2 months or so, variance sequence D is obtained by step 3,4mnAnd by itself and this 2
The middle of the month daily actual measurement soil moisture sequence SmnContrasted.Signal-to-noise ratio data file is sequentially arranged, while will be real
Survey soil moisture data file to be sequentially arranged, finally both variation tendencies are plotted in a figure, establish variance
The functional relation of variation tendency and soil moisture change trend.
Fig. 6 is variance and surveys humidity changing trend diagram, and 13 represent soil moisture change curves in figure, and 14 represent that variances become
Change curve, variance reaches 0.71 with surveying the correlation of humidity, and trend is coincide substantially, when humidity value is less, variance
It is smaller, illustrate that the fluctuation of reflectance factor is smaller.After November 24 and November 27 rain, variance yields becomes big, illustrates reflection system
Several fluctuations becomes big, further illustrates that the relative fluctuation of Big Dipper direct signal and reflected signal becomes big.
Fig. 6 is the empirical relation model of variance and soil moisture, and its expression formula is as follows：
S=1.97*ln (d)+15.48
Wherein, s is actual measurement soil humidity value, and d is variance yields.
In the figure 7,15 represent that abscissas represent variance, ordinate represents the point of soil moisture, the expression formula of the point for (D,
S), 16 be the logarithmic function empirical model being fitted, and the logarithmic relationship curve that these points are fitted substantially as can be drawn from Figure 7 is attached
Closely.
Step 6：Estimate soil moisture using logarithmic function relation
Finally i.e. using the model, soil moisture is estimated using the big-dipper satellite signal-to-noise ratio data on the same day.Foundation should
Relation, calculate certain day Big Dipper signal reflex coefficient variance after can estimate the ground on the day of soil moisture.
Claims (4)
- A kind of 1. soil moisture method of estimation based on Big Dipper GEO satellite signal, it is characterised in that：The signal-to-noise ratio data of the soil moisture change direct signal of more obvious 2 months and reflected signal is first obtained, then is obtained The ratio of reflected signal and direct signal is worth to reflectance factor, asks for variance to it, compares the correlation of variance and true humidity, Then variance and humidity are carried out curve fitting, establishes the functional relation of variance and soil moisture, finally according to the functional relation, The humidity value on the same day is estimated by certain day Big Dipper GEO satellite Signal-to-Noise data.
- 2. the soil moisture method of estimation according to claim 1 based on Big Dipper GEO satellite signal, it is characterised in that：Tool Body comprises the following steps；Step 1：Overlay area determines and raw data acquisitionOverlay area is determined according to the position and height of the elevation bearing angle of Big Dipper GEO satellite and reception antenna；Utilize dextrorotation Poliarizing antenna receives direct signal, and left-hand polarized antenna receives reflected signal, then receives two days by CPU DTU The signal that line transmits, the signal to noise ratio of output Big Dipper GEO satellite signal, the elevation angle, azimuth, UTC time information, finally passes data Onto server；Step 2：Data preselectSelect in direct signal and reflected signal, whole day there are the data of signal to noise ratio for 24 hours as pending data source；Step 3：Big Dipper Signal PretreatmentUTC time that the GEO satellite signal received is included, the elevation angle, azimuth, signal to noise ratio data in signal to noise ratio with UTC time information extracts, and respectively by direct signal and the time unifying of reflected signal, then ask for reflectance value；Step 4：Ask for varianceThe variances of per 1800 reflectance factors of period half an hour is asked for respectively to reflect the fluctuation situation of reflectance factor；Step 5：Compare the Long-term change trend relation of variance and soil moisture and be fitted both empirical models；Step 6：Rule of thumb model estimation soil moisture.
- 3. the soil moisture method of estimation according to claim 2 based on Big Dipper GEO satellite signal, it is characterised in that：Institute The specific implementation process for stating step 5 is；The continuous processing signal-to-noise ratio data of 2 months, utilizes reflectance factor and signal to noise ratio formula, it is known that signal to noise ratio is obtained per second anti- Coefficient value is penetrated, the variance yields of reflectance factor is finally calculated, its actual measurement soil humidity value daily with 2 middle of the month is contrasted, This 2 months variance is sequentially arranged, and this 2 months soil moisture value is sequentially arranged, finally by two Person is plotted in a figure, and the logarithmic function relation of variance and soil moisture is established by nonlinear regression analysis.
- 4. the soil moisture method of estimation according to claim 3 based on Big Dipper GEO satellite signal, it is characterised in that：Institute Step 6 is stated using logarithmic function relation to estimate soil moisture；After the big-dipper satellite signal-to-noise ratio data for obtaining certain day certain period half an hour, period half an hour is obtained by data processing Variance yields, the soil moisture of the period can be obtained by substituting into logarithmic function relation.
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| CN106093076B (en) * | 2016-05-23 | 2019-03-08 | 北京航空航天大学 | A kind of soil humidity measuring device based on GNSS interference power peak-to-valley value |
| CN106767383A (en) * | 2016-11-11 | 2017-05-31 | 清华大学 | The measuring method of the snow depth based on continuous operation GNSS stations signal-to-noise ratio data |
| US10996179B2 (en) | 2019-03-11 | 2021-05-04 | Skaha Remote Sensing Ltd. | System and method to detect ground moisture |
| CN110673147A (en) * | 2019-10-16 | 2020-01-10 | 西安科技大学 | Post-flood evaluation method |
| CN111337552A (en) * | 2020-03-13 | 2020-06-26 | 山东航向电子科技有限公司 | Signal reconstruction method and soil humidity interferometric method based on same |
| CN111337548A (en) * | 2020-03-13 | 2020-06-26 | 山东航向电子科技有限公司 | High-precision signal-to-noise ratio fitting model and soil humidity inversion method based on same |
| CN113039915B (en) * | 2021-03-30 | 2022-03-11 | 中慧高芯技术(山东)有限公司 | Farmland irrigation system based on Internet of things and data calculation and analysis |
| CN114839354B (en) * | 2022-07-02 | 2022-11-18 | 杭州电子科技大学 | Beidou and GPS soil humidity measurement method based on sliding algorithm and weighting strategy |
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