CN114755641A - Cross radiometric calibration and verification method for artificial ground objects and natural ground objects - Google Patents

Cross radiometric calibration and verification method for artificial ground objects and natural ground objects Download PDF

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CN114755641A
CN114755641A CN202210055904.9A CN202210055904A CN114755641A CN 114755641 A CN114755641 A CN 114755641A CN 202210055904 A CN202210055904 A CN 202210055904A CN 114755641 A CN114755641 A CN 114755641A
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calibration
artificial
cross
radiometric
natural
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李慧娟
张恒
张玮
王爱春
陈琦
张立峰
石晓宇
侯明辉
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China Center for Resource Satellite Data and Applications CRESDA
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G01S7/4052—Means for monitoring or calibrating by simulation of echoes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
    • G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
    • G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
    • G01S13/9021—SAR image post-processing techniques
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S2013/0236—Special technical features
    • G01S2013/0245—Radar with phased array antenna

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Abstract

The invention relates to a cross radiometric calibration and verification method for artificial and natural ground objects, which comprises the following steps: calibrating the radar cross section of the active calibrator, and measuring the nominal RCS of the active calibrator; arranging an active calibrator and a three-plane reflector of a known nominal RCS in a surveying and mapping band, and acquiring original data of a calibration field after a GF-3 satellite passes through the top; imaging the original data to obtain a single-view complex SAR image, calibrating the position of each artificial ground object calibrator in the image, extracting point target response energy and calculating an absolute radiometric calibration constant; based on the calibration constant, the backscattering coefficient is measured by using the tropical rainforest natural land feature data with the same mode and wave position, and the absolute radiation precision is calculated. The method is based on satellite measured data, and adopts an artificial ground object and natural ground object cross radiation calibration method to periodically update and verify the partial wave position calibration result of the satellite, thereby effectively increasing the accuracy of the absolute radiation calibration constant measurement value and realizing quantitative monitoring of the performance state and stability of the GF-3 satellite in orbit operation.

Description

Cross radiometric calibration and verification method for artificial ground objects and natural ground objects
Technical Field
The invention belongs to the field of satellite-borne synthetic aperture radar data processing, and relates to a cross radiation calibration and verification technology for artificial ground objects and natural ground objects in a high-resolution three-satellite calibration test in China.
Background
The high-resolution three-number (GF-3) satellite is a 1-meter-resolution C-band multipolar Synthetic Aperture Radar (SAR) imaging satellite with high-resolution imaging capability, is the only phased array radar imaging satellite in high-resolution special (civil) and is also the first C-band multipolar high-resolution microwave remote sensing satellite in China. The GF-3 satellite is a microwave remote sensing satellite with sun synchronous regression freezing orbit operation, can realize the monitoring and monitoring of global ocean and land information in all weather, flexibly expands the earth observation range through left and right postures and improves the quick response capability, and the acquired C-band multi-polarization microwave remote sensing information can be used in multiple fields of ocean, disaster reduction, water conservancy, weather and the like, serves multiple industries and business departments of ocean, disaster reduction, water conservancy, weather and the like in China, and is an important technical support for implementing ocean development, land environment resource monitoring, disaster prevention and disaster reduction in China.
The multi-direction and multi-field application of the GF-3 satellite means that the traditional qualitative remote sensing is difficult to meet the high-precision imaging requirement of the traditional qualitative remote sensing, and a satellite SAR system has a plurality of gain errors in signal flow processing, so that the produced SAR image cannot accurately reflect the echo characteristics of an actual ground object, and the SAR high-resolution image acquisition is directly influenced, therefore, various errors, such as an on-orbit error, a propagation error, an external calibration error and the like, must be compensated through the calibration processing of the SAR to realize the quantitative observation of the ground, thereby improving the stability of satellite imaging, and the quantitative remote sensing technology gradually becomes an important means for optimizing the performance of a satellite-borne synthetic aperture radar system.
The space-borne SAR radiometric calibration technology is a key step for realizing quantitative remote sensing, and the radiometric calibration is divided into inner calibration and outer calibration, wherein the performance of a radar system is calibrated by measuring the amplitude-phase characteristics of an antenna TR channel and a system reference function through internal equipment of the SAR system, and the radiometric outer calibration is calibrated by adopting a corner reflector or an active calibrator to reflect signals in an external field test. In the field of satellite-borne SAR radiometric calibration processing, the development of China is relatively late abroad, particularly for a outfield radiometric calibration test, domestic research is mostly limited to radiometric calibration simulation verification, analysis of calibration processing by using actual measurement data is lacked, and research of a cross radiometric calibration technology by using artificial ground objects and natural ground objects is lacked, so that the process of carrying out the cross radiometric calibration related technology of the artificial ground objects and the natural ground objects by using satellite actual measurement data is refined, SAR calibration precision inspection and verification methods are deeply analyzed, and the method has important research significance for obtaining high-radiometric-precision SAR image products.
Disclosure of Invention
The invention solves the technical problems that: the method is characterized in that the defects of the prior art are overcome, a cross-radiometric calibration and verification method for artificial and natural ground objects is provided aiming at the problems faced by the existing radiometric calibration data processing, a method and a result of measuring the overall transfer function (calibration constant) of a radar system by using the artificial objects such as a corner reflector are given, and a data verification result of the measured same-wave-position Amazon tropical rainforest natural ground objects is used.
The technical scheme of the invention is as follows: a cross radiometric calibration and verification method for artificial and natural features comprises the following steps:
(1) calibrating the radar cross section of the active calibrator in an external field calibration test, and measuring a nominal RCS (radar cross section) measurement value sigma of the active calibrator;
(2) arranging an active calibrator for precise calibration and a dihedral corner reflector with a known nominal value RCS in a surveying and mapping band, and acquiring the original data of a calibration field of a GF-3 satellite passing through the top;
(3) imaging the original data of the calibration field to obtain LEVEL1A LEVEL single-view complex SAR image, and then performing precision processingRadiation correction, namely, calibrating the position of each artificial ground object calibrator in the SAR image, extracting point target response energy and calculating an absolute radiation calibration constant; calculating the mean value thereof
Figure BDA0003476466740000021
By mean value
Figure BDA0003476466740000022
As the scaling constant of the scene image;
(4) and based on the absolute radiometric calibration constant obtained by artificial ground feature calculation, carrying out backscattering coefficient measurement by using the data of the thermal zone rainforest natural ground features with the same mode and the same wave position to check the absolute radiometric precision.
The specific process of the step (1) is as follows: firstly, a transmitting antenna of an active scaler is used for transmitting a pulse signal with fixed carrier frequency, a receiving antenna receives a reflected signal, the signal is transmitted by the transmitting antenna after time delay amplification, echo signals are sampled and recorded, and then the nominal RCS measurement of the active scaler can be completed by using the fixed relation between the power difference delta P of the two echo signals and the RCS of the radar cross section.
The fixed relation between the power difference value delta P of the two echo signals and the radar cross section RCS is as follows:
Figure BDA0003476466740000031
wherein: σ is the nominal RCS measurement of the active scaler;
r is the distance from the standard reflector to the active scaler;
σrefis the radar cross-sectional area of a standard reflector.
The specific process of the step (2) is as follows: firstly, an active calibrator which is measured by a nominal RCS value and a three-surface corner reflector with a known nominal value are arranged in a surveying and mapping zone of an SAR scaling field of a Chinese Eyork flag, then, planning and arranging of a satellite imaging task are carried out according to longitude and latitude coordinates of the scaling field, an instruction is generated and noted, and original data of the scaling field of a satellite passing the top are obtained.
The specific process of the step (3) is as follows: in order to measure the absolute radiometric calibration constant of the artificial ground object calibrator, firstly, the acquired calibration field original data is processed to obtain a single-view complex SAR image, the point target position of each artificial ground object calibrator is calibrated in the image, the point target response energy is extracted, the calibration constant of each point target is calculated, and then the calibration constants of all the point targets are averaged to obtain the absolute radiometric calibration constant.
Scaling constant of said each point target
Figure BDA0003476466740000032
εp: point target energy response, P in the corresponding equation d；
σref: the reference point target radar cross section;
Rt: the target slope distance of the point;
θt: a point target incident angle;
R0: a reference slope distance;
Pt0: a transmit power;
G2(θn,φn): a single-pass antenna pattern;
Get: the system gain;
Ptt: a reference transmit power;
θ0: a reference incident angle;
Figure BDA0003476466740000041
an azimuth angle;
Figure BDA0003476466740000042
the azimuth is referenced.
The specific process of the step (4) is as follows: firstly, selecting tropical rainforest natural ground object data which have the same mode and wave position with calibration field data, calculating the backscattering coefficient of the natural ground object based on a calibration constant value in a reverse-deducing mode, and obtaining a difference value with the backscattering coefficient value of the internationally recognized C wave band rainforest to obtain an absolute radiation precision value, and verifying the accuracy of a calibration constant measurement value.
And if the absolute radiation precision value is less than 1dB, the verification accuracy is successful.
Compared with the prior art, the invention has the advantages that:
(1) according to the method, original echo data of a latest inner Mongolia Eschel flag external field calibration test of a GF-3 satellite are adopted, a GF-3 ground processing system is used for imaging and product production, and an LEVEL 1A-LEVEL single-view complex SAR image is obtained.
(2) The invention simultaneously uses two scalers, namely a corner reflector and an active scaler, to measure an absolute radiometric calibration constant so as to carry out mutual reference and verification, further adopts near-term Amazon tropical rainforest co-wave position imaging data of a GF-3 satellite, and assists in verifying the calibration constant by measuring a backward scattering coefficient. Therefore, the method carries out cross calibration and verification based on both artificial ground features (corner reflectors and active calibrators) and natural ground features (Amazon tropical rainforest), and effectively increases the accuracy of the absolute radiometric calibration constant measurement value.
Drawings
Fig. 1 is a schematic diagram of the working principle of radar cross-sectional area calibration.
FIG. 2 is a schematic diagram of the layout of the calibration apparatus.
FIG. 3 is a flow chart of absolute calibration constant measurement.
Fig. 4 is a schematic diagram of the positions of the artificial ground object scalers in the SAR image.
FIG. 5 is a histogram of the scaling constant mean of HH modes at different wave positions for the active sealer and corner reflector.
FIG. 6 is a schematic diagram of a target distribution.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings in which:
step 1, calibrating the radar cross section of the active scaler in an external field scaling test, and measuring the nominal RCS of the active scaler.
The working principle of radar cross-sectional area calibration is shown in fig. 1. The radar cross-sectional area calibration of the active scaler calibration system is an important device for ensuring the accuracy of the RCS of the active scaler, and mainly provides an accurately known radar cross-sectional area reference value for the active scaler to measure the nominal RCS of the active scaler. When the active scaler carries out RCS calibration, a transmitting antenna of the active scaler transmits a pulse signal of fixed carrier frequency generated by an internal signal generator, a receiving antenna receives a signal reflected by a standard reflector, the reflected signal is transmitted by the transmitting antenna after being delayed and amplified by a forwarding path of the active scaler, and an internal detection recording system carries out sampling recording on an echo signal. The difference between the powers of the two adjacent recorded echo signals is as follows:
Figure BDA0003476466740000051
wherein: σ is the nominal RCS measurement of the active scaler;
r is the distance from the standard reflector to the active scaler;
σrefis the radar cross-sectional area of a standard reflector.
The above formula shows σrefAnd after R is determined, the radar cross section of the active scaler is determined by the power difference delta P of two adjacent echo signals. A gain calibration circuit arranged in the source scaler detects the power of the signal source as P 0Power P of pulse signal coupled with transmitting terminal1The difference Δ P ═ P1/P0The method is used as a reference value for controlling the gain of a forwarding channel by a gain calibration circuit when the active scaler actually works so as to keep the stability of the radar cross-sectional area sigma of the active scaler determined by self-calibration.
And step 2, laying the precisely calibrated active calibrator and the three-surface corner reflector with the known nominal value RCS in the surveying and mapping band, and acquiring the calibration field original data of the GF-3 satellite after passing the top.
The calibration device for participating in the GF-3 satellite external field test comprises: 9C-band active scalers and 8 corner reflectors. And according to the main application of the calibration equipment and the test requirement of external field calibration, measuring the absolute radiation calibration constant. A schematic diagram of the layout of the targeting device is shown in fig. 2.
And 3, imaging the calibration field original data to obtain a LEVEL1A LEVEL single-view complex SAR image, then performing precise radiometric correction, calibrating the position of each artificial terrestrial object calibrator in the SAR image, extracting point target response energy and calculating an absolute radiometric calibration constant.
The method adopts GF-3 satellite fine strips 1, fine strips 2, full polarization strips 1, sliding bunching, standard strips and hyperfine strip calibration field data to participate in the test, and the test area is the inner Mongolia autonomous region Orthomson Erdos city Eltorke flag SAR calibration field. Absolute radiometric calibration constant measurements rely on the ground to provide a target of precisely known radar cross-sectional area (or scattering coefficient) as a standard reference source for measurements. In an outer calibration field positioned in inner Mongolia, according to selected wave position parameters to be measured, precise orbit data of a satellite and the like, calibration and calibration software is used for analyzing the wave beam coverage condition, a proper layout place is selected, equipment working parameter information is calculated, a polarization active calibrator of known precise RCS is laid out and working parameters of the polarization active calibrator are set, the polarization active calibrator is used as a reference target to carry out SAR system transfer function, the active calibrator and a corner reflector which are precisely calibrated are laid in a surveying and mapping zone, imaging processing is carried out on original data of the calibration field after a radar passes through the top, precise radiation correction is carried out in the imaging processing process, the image position of each calibrator is determined on an image, point target response energy is extracted, and a calibration constant of each point target is calculated, namely measurement of an absolute radiation calibration constant is carried out.
The principle of absolute radiometric calibration constant measurement is as follows. The actually measured radar cross section sigma' of the point target on the SAR image can be expressed as shown in the following formula:
Figure BDA0003476466740000061
in the formula:
Figure BDA0003476466740000062
image pixel power value (dB) after removing noise power
Figure BDA0003476466740000063
Point target corresponds to the square of the DN value of image element (i, j)
Figure BDA0003476466740000064
Squaring of system noise DN values
K: scaling constant (dB)
Rn: oblique distance (Rice)
R0: reference slope distance (rice)
Pt0: transmitting power (Tile)
Ptn: reference transmission power (Tile)
θn: incident angle (degree)
θ0: reference angle of incidence (degree)
φn: azimuth (degree)
φ0: reference azimuth angle (degree)
G2(θn,φn): single pass antenna pattern
Gen: gain of system
Geo: reference system gain
Figure BDA0003476466740000071
In the formula (I), the compound is shown in the specification,
εp: point target energy response, P in the corresponding equationd
σref: reference point target radar cross section (dB)
Rt: target oblique distance (rice)
θt: point target incident angle (degree)
In summary, the absolute radiometric calibration constant measurement flow chart is shown in fig. 3, and the measurement scheme is as follows:
(1) active scaler or corner reflector providing accurate radar cross-section reference value sigmaref；
(2) Imaging and relative radiation correction of the calibration field data;
(3) measuring target response energy of active scaler and corner reflector from corrected scale field image, and calculating scaling constant KiCalculating the mean value thereof
Figure BDA0003476466740000073
By mean value
Figure BDA0003476466740000072
As the scaling constant of the scene image.
According to the principle and scheme for measuring absolute radiometric calibration constants, taking fine band 2 mode (WF6 wave bits, 26918 circles) as an example, the positions of the artificial surface feature calibrators in the SAR image are calibrated as shown in fig. 4, and through the above calculation process, the calibration constant measurement result table of each calibrator is obtained as shown below.
TABLE 1 Fine Bandwidth 2 mode (WF6 WAVE BIT) corner Reflector scaling constant measurement results Table
Figure BDA0003476466740000081
TABLE 2 Fine banding 2 mode (WF6 wave position) active scaler scaling constant measurement results table
Figure BDA0003476466740000082
The fine band 2 mode (WF6 wave position) corner reflector and active scaler scaling constants from tables 1 and 2 are 26.6667 and 26.2593, respectively. And analogizing to obtain absolute radiometric calibration constant measurement values of 6 modes and 16 wave positions, and drawing a calibration constant mean histogram of HH modes of the active calibrator and the corner reflector under different wave positions to compare relative measurement errors of the calibration constant mean histogram, as shown in FIG. 5. As can be seen from the comparison of the histograms, the measurement results of the calibration constants based on the corner reflector and the active scaler are very close or equivalent and can be mutually referred or verified.
And 4, based on the absolute radiometric calibration constant obtained by calculating the artificial ground feature, carrying out backscattering coefficient measurement by using the data of the tropical rainforest natural ground features with the same mode and the same wave position to test the absolute radiometric precision.
Taking the single-view complex data of the mode 2 (WF6 wave bits) LEVEL1A of the GF-3 satellite fine band as an example, based on the scaling constant mean value 26.463 of both the corner reflector and the active scaler in step 2, the same WF6 wave is selected to pass through the Amazon tropical rainforest, and the target distribution is shown in FIG. 6, and the results are shown in the following Table 3.
TABLE 3 Fine band 2 mode (WF6 wave position) Table of the results of the backscattering coefficient measurements for rainforest tropics
Figure BDA0003476466740000091
According to the internationally recognized results, the C-band backscattering coefficient of Amazon rainforest is-6.4 dB, the backscattering coefficient of the fine band 2 mode (WF6 wave position) rainforest is-6.3611 dB according to the result in Table 3, and the difference value of the backscattering coefficient of the C-band rainforest from the internationally recognized Amazon rainforest is 0.0389dB, so that the calculated value of the calibration constant in the step 2 is successfully verified to have high accuracy through cross calibration of artificial and natural ground objects.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention.

Claims (8)

1. A cross radiometric calibration and verification method for artificial and natural features is characterized by comprising the following steps:
(1) calibrating the radar cross section of the active calibrator in an external field calibration test, and measuring a nominal RCS (radar cross section) measurement value sigma of the active calibrator;
(2) arranging an active calibrator for precise calibration and a three-surface corner reflector with a known nominal value RCS in a surveying and mapping zone, and acquiring the original data of a calibration field after the satellite passes through the top;
(3) imaging the calibration field original data to obtain a LEVEL1A LEVEL single-vision complex SAR image, then performing precise radiometric correction, calibrating the position of each artificial ground object calibrator in the SAR image, extracting point target response energy and calculating an absolute radiometric calibration constant; calculating the mean value thereof
Figure FDA0003476466730000012
By mean value
Figure FDA0003476466730000013
As the scaling constant of the scene image;
(4) and based on the absolute radiometric calibration constant obtained by artificial ground feature calculation, carrying out backscattering coefficient measurement by using the data of the tropical rainforest natural ground features with the same mode and the same wave position to check the absolute radiometric precision.
2. The method of claim 1, wherein the artificial and natural feature cross-radiometric calibration and verification method comprises: the specific process of the step (1) is as follows: firstly, a transmitting antenna of the active scaler is used for transmitting a pulse signal with a fixed carrier frequency, a receiving antenna is used for receiving a reflected signal, the signal is transmitted by the transmitting antenna after time delay amplification, echo signals are sampled and recorded, and then the nominal RCS measurement of the active scaler is completed by using the fixed relation between the power difference value delta P of the echo signals and the radar sectional area RCS.
3. The method of claim 2, wherein the artificial and natural feature cross-radiometric calibration and verification method comprises: the fixed relation between the power difference value delta P of the two echo signals and the radar cross section RCS is as follows:
Figure FDA0003476466730000011
wherein: σ is the nominal RCS measurement of the active scaler;
r is the distance from the standard reflector to the active scaler;
σrefis the radar cross-sectional area of a standard reflector.
4. The method of claim 1, wherein the artificial and natural feature cross-radiometric calibration and verification method comprises: the specific process of the step (2) is as follows: firstly, an active scaler which is measured by a nominal RCS value and a three-surface corner reflector with a known nominal value are arranged in a surveying and mapping zone of an SAR calibration field, then, the satellite imaging task planning arrangement is carried out according to the longitude and latitude coordinates of the calibration field, an instruction is generated and the instruction is added, and the original data of the calibration field with the satellite passing through the top is obtained.
5. The method of claim 1, wherein the artificial and natural feature cross-radiometric calibration and verification method comprises: the specific process of the step (3) is as follows: in order to measure the absolute radiometric calibration constant of the artificial ground object calibrator, firstly, the acquired calibration field original data is processed to obtain a single-view complex SAR image, the point target position of each artificial ground object calibrator is calibrated in the image, the point target response energy is extracted, the calibration constant of each point target is calculated, and then the calibration constants of all the point targets are averaged to obtain the absolute radiometric calibration constant.
6. The method of claim 5, wherein the artificial and natural feature cross-radiometric calibration and verification method comprises: scaling constant of each point target
Figure FDA0003476466730000021
εp: point target energy response, P in the corresponding equationd；
σref: reference point target radar cross-sectional area;
Rt: the target slope distance of the point;
θt: a point target incident angle;
R0: a reference slope distance;
Pt0: a transmit power;
G2(θn,φn): a single-pass antenna pattern;
Get: a system gain;
Ptt: a reference transmit power;
θ0: a reference incident angle;
Figure FDA0003476466730000031
an azimuth angle;
Figure FDA0003476466730000032
the azimuth is referenced.
7. The method of claim 1, wherein the artificial and natural feature cross-radiometric calibration and verification method comprises: the specific process of the step (4) is as follows: firstly, tropical rainforest natural land feature data in the same mode and wave position as calibration field data are selected, backscattering coefficients of the natural land features are calculated based on a calibration constant value in a reverse-deducing mode, a difference value is obtained between the backscattering coefficients of the tropical rainforest natural land features and the backscattering coefficient value of the C-band rainforest, an absolute radiation precision value is obtained, and accuracy of a calibration constant measurement value is verified.
8. The method of claim 7, wherein the artificial and natural feature cross-radiometric calibration and verification method comprises: and if the absolute radiation precision value is less than 1dB, the verification accuracy is successful.
CN202210055904.9A 2022-01-18 2022-01-18 Cross radiometric calibration and verification method for artificial ground objects and natural ground objects Pending CN114755641A (en)

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