Disclosure of Invention
The invention aims to provide a method for monitoring the deformation of a power transmission iron tower by using a foundation SAR of an artificial corner reflector, aiming at overcoming the defects of the prior art, and the method is used for accurately identifying the target of the corner reflector on the iron tower and realizing the high-precision deformation monitoring of the power transmission iron tower.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a method for monitoring deformation of a power transmission tower by using a foundation SAR (synthetic aperture radar) based on an artificial corner reflector, which comprises the following steps of:
s1, acquiring ground SAR time sequence image data of a monitoring area foundation including a power transmission iron tower and a reference point corner reflector, measuring geographic coordinates of an iron tower CR and a reference point CR, inputting the geographic coordinates as initial data into the iron tower CR point phase time sequence analysis software module, and calculating the coordinate point position of the CR in the SAR image by utilizing an SAR constellation equation;
determining the row and column number of the CR in the SAR image through the coordinate points, wherein the formula is as follows:
wherein the content of the first and second substances,
and
position vectors of the sensor and the target point, respectively;
and
velocity vectors of the sensor and the target point, respectively;
is a radar wavelength, obtained by imaging parameters;
is the Doppler frequency;
is the distance between the sensor to the target point;
s2, adopting GMT local time to carry out data diversity, generating a data set every 24 hours, wherein the reference point CR is selected as a stable point around the iron tower and used as a starting point of phase unwrapping of the interferogram, and CR point phases are obtained through the phase unwrapping, and the CR point phases comprise the following parts:
wherein the content of the first and second substances,
the phase of the CR point after the t interference pattern is unwrapped;
a deformation phase of CR;
for atmospheric phase, solving by model and interpolation;
calculating the phase caused by thermal expansion according to the temperature and the thermal expansion coefficient;
for phase errors caused by noise points, the noise phase is ignored due to the good ground-based SAR coherence.
Further, still include: s3, establishing a monitoring area by using an unmanned aerial vehicle LiDAR, and establishing an iron tower stress model by combining the iron tower trend and the power transmission line extension direction; the iron tower stress model takes the extending direction of a power transmission conductor as the longitudinal direction, and takes the direction which is supposed to be vertical to the extending direction of the conductor on the iron tower as the lateral direction, so as to carry out the local decomposition of the stress of the power transmission iron tower;
when the tower type and the line are tangent towers, the stressed longitudinal direction and the stressed lateral direction of the iron towers on all the straight lines are in the same coordinate system;
when the iron tower is a corner tower or a corner exists in the extension direction of the power transmission line, the longitudinal direction and the lateral direction of the iron tower are respectively set according to the front and rear iron tower directions and the wire extension direction.
Further, based on the stress model of the iron tower and the 24-hour air temperature change characteristics, carrying out the daily period modeling analysis of the thermal expansion of the iron tower, extracting the CR phase periodic change data caused by the thermal expansion of the iron tower, and establishing a corresponding deformation model as follows:
wherein the content of the first and second substances,
is the length of the time base of the interferogram;
is the thermal expansion coefficient of the iron tower.
Further, SAR time series image data based on the SAR time;
when an SAR observation sampling interval is short or the atmosphere in a scene is homogeneous, a distance-phase function model is constructed by using corresponding information of a stable point outside an iron tower target area in the SAR image interferogram sequence to simulate an atmosphere phase screen and is used for eliminating the atmospheric error in the SAR image interferogram, wherein the distance-phase function model is as follows:
wherein the content of the first and second substances,
the unwrapped phase value of the ith stable pixel element;
the slope distance of the ith pixel element;
the atmospheric delay coefficient to be solved;
when the SAR observation sampling interval is long or the atmosphere in the scene is non-homogeneous, the iron tower and the CR target are firstly masked by using the strength information of the iron tower and the CR target, and the atmospheric phase of the iron tower and the CR target is interpolated by using the filtering phase of the stable point outside the iron tower target area, so that the atmospheric error of CR is eliminated.
Further, in S2, the phase unwrapping is that when the deformation phase of the iron tower exceeds pi/2 in one data set, a phase jump is generated, so that the deformation result is distorted, and a phase accumulation integral and a phase jump estimation method of the SAR time series image data are used to find out the phase jump caused by the deformation magnitude, accurately accumulate phase ambiguity integers, and accurately extract the deformation of the iron tower in a single data set.
Further, in S3, when the tower shape and the line are tangent towers, the stressed longitudinal direction and the stressed lateral direction of the iron tower on all the straight lines are in the same coordinate system, and when the iron tower is stressed by settlement, the longitudinal deformation is caused
Decomposition of deformation from the line of sight of radar
The conversion formula is as follows:
wherein the content of the first and second substances,
longitudinal deformation;
elevation angle for ground based SAR beams;
for solving the CR deformation, the calculation formula needs to be combined with the radar wavelength
Comprises the following steps:
when the iron tower is subjected to transverse traction force, the iron tower deforms laterally
Can be decomposed by deformation of radar line of sight
The conversion formula of (1) is as follows:
wherein the content of the first and second substances,
is laterally deformed.
The invention has the beneficial effects that: the method comprises the steps of utilizing a foundation SAR to aim at an artificial Corner Reflector (CR) fixed on a power transmission iron tower for scanning to obtain a time sequence SAR sequence image, utilizing a constellation equation to extract a phase sequence of a pixel where a CR target is located from the time sequence image, and then utilizing a three-dimensional space-time phase unwrapping method to obtain a deformation result of the corner reflector for iron tower deformation monitoring. A daily cycle thermal expansion model, an atmospheric error model, a breeze vibration model, a phase jump detection algorithm and a coherence iterative analysis technology are introduced into CR data processing to realize accurate acquisition of the deformation phase of the CR point of the iron tower. And finally, establishing an iron tower stress model based on the extending direction of the transmission conductor, decomposing the deformation quantity acquired by the ground SAR into a two-dimensional space, and realizing accurate calculation of the deformation and the inclination of the iron tower.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1, a method for monitoring deformation of a power transmission tower by using a ground-based SAR of an artificial corner reflector includes the following steps:
s1, acquiring ground SAR time sequence image data of a monitoring area foundation including a power transmission iron tower and a reference point corner reflector, measuring geographic coordinates of an iron tower CR (artificial corner reflector) and the reference point CR, inputting the data into the iron tower CR point phase time sequence analysis software module as initial data, and calculating coordinate point positions of all CRs in the SAR image by utilizing an SAR constellation equation;
wherein, the iron tower CR is a CR placed on the iron tower; the reference point CR is CR placed at the reference point.
Determining the row and column number of the CR in the SAR image through the coordinate points, wherein the formula is as follows:
wherein the content of the first and second substances,
and
position vectors of the sensor and the target point, respectively;
and
velocity vectors of the sensor and the target point, respectively;
is a radar wavelength, obtained by imaging parameters;
is the Doppler frequency;
is the distance between the sensor to the target point;
that is, the combination parameter file can be
And
the row and column numbers of the CR dots are converted.
The ground-based SAR device comprises a transmitting antenna (a part of linear scanning device comprising an antenna orbit);
the CR is fixed on the power transmission iron tower and is properly adjusted according to the scanning direction of the ground SAR so that the axis direction of the CR is aligned to the direction of the ground SAR wave beam;
s2, performing data diversity by adopting GMT local time, and generating a data set every 24 hours, wherein the data for performing the data diversity is acquired by ground-based SAR scanning;
referring to fig. 2, the reference point CR should be selected as a stable point around the iron tower, and used as a starting point for phase unwrapping of the interferogram, and a CR point phase is obtained through phase unwrapping, where the CR point phase includes the following parts:
wherein the content of the first and second substances,
the phase of the CR point after the t interference pattern is unwrapped;
a deformation phase of CR;
for atmospheric phase, solving by model and interpolation;
calculating the phase caused by thermal expansion according to the temperature and the thermal expansion coefficient;
for phase errors caused by noise points, the noise phase is ignored due to the good ground-based SAR coherence.
Wherein the function of the formula (2) is to obtain
By the obtained
And judging the deformation degree of the iron tower according to the value.
Further comprising: s3, establishing a monitoring area by using an unmanned aerial vehicle LiDAR (laser radar technology), and establishing an iron tower stress model by combining the iron tower trend and the power transmission line extension direction; the iron tower stress model takes the extending direction of a power transmission conductor as the longitudinal direction, and takes the direction which is supposed to be vertical to the extending direction of the conductor on the iron tower as the lateral direction, so as to carry out the local decomposition of the stress of the power transmission iron tower;
the monitoring area comprises a three-dimensional point cloud model of the power transmission tower;
when the tower type and the line are tangent towers, the stressed longitudinal direction and the stressed lateral direction of the iron towers on all the straight lines are in the same coordinate system;
when the iron tower is a corner tower or a corner exists in the extension direction of the power transmission line, the longitudinal direction and the lateral direction of the iron tower are respectively set according to the front and rear iron tower directions and the wire extension direction.
Further comprising: based on the stress model of the iron tower and the 24-hour air temperature change characteristics, carrying out modeling analysis on the daily period of thermal expansion of the iron tower, extracting CR phase periodic change data caused by the thermal expansion of the iron tower, and establishing a corresponding deformation model as follows:
wherein the content of the first and second substances,
for the interferenceThe time base length of the graph;
is the thermal expansion coefficient of the iron tower.
Thus, in the formula (2) is obtained,
the value of (c).
Based on the SAR time sequence image data, the situation that when the SAR observation sampling interval is short or the atmosphere in the scene is homogeneous and the situation that when the SAR observation sampling interval is long or the atmosphere in the scene is inhomogeneous can be obtained;
when an SAR observation sampling interval is short or the atmosphere in a scene is homogeneous, a distance-phase function model is constructed by using corresponding information of a stable point outside an iron tower target area in the SAR image interferogram sequence to simulate an atmosphere phase screen and is used for eliminating the atmospheric error in the SAR image interferogram, wherein the distance-phase function model is as follows:
wherein the content of the first and second substances,
the unwrapped phase value of the ith stable pixel element;
the slope distance of the ith pixel element;
the atmospheric delay coefficient to be solved;
thus, in the formula (2) obtained by solving,
an atmospheric phase value;
when the SAR observation sampling interval is long or the atmosphere in the scene is non-homogeneous, the iron tower and the CR target are firstly masked by using the strength information of the iron tower and the CR target, and the atmospheric phase of the iron tower and the CR target is interpolated by using the filtering phase of the stable point outside the iron tower target area, so that the atmospheric error of CR is eliminated.
In the embodiment of the present invention, since in the formula (2),
and the CR point phase after the interference pattern unwrapping is obtained by phase unwrapping the original interference pattern.
Atmospheric phase value
Can be obtained by the formula (4);
phase value caused by thermal expansion
Can be obtained by the formula (3);
phase error caused by noise point
Can be omitted;
the deformed phase value of CR can be obtained by the formula (2)
。
In S2, the phase unwrapping process includes: and when the deformation phase of the iron tower exceeds pi/2 in one data set, phase jump is generated to distort the deformation result, and the phase jump caused by the deformation magnitude is found out by adopting the phase accumulated integral and phase jump estimation method of the SAR time sequence image data, the phase ambiguity integer is accurately accumulated, and the accurate extraction of the deformation of the iron tower in a single data set is realized.
Because the stress of the iron tower mainly comprises the tower shape and the line of the iron tower being a tangent tower and the iron tower being a corner tower or the extension direction of the power transmission line having a corner,
referring to fig. 3, in particular,when the tower type and the line are tangent towers, the stressed iron towers on all the straight lines have longitudinal and lateral directions in the same coordinate system, and when the iron towers are subjected to settlement stress, the iron towers deform longitudinally
Decomposition of deformation from the line of sight of radar
The conversion formula is as follows:
wherein the content of the first and second substances,
longitudinal deformation;
elevation angle for ground based SAR beams;
for solving the CR deformation, the calculation formula needs to be combined with the radar wavelength
Comprises the following steps:
when the iron tower is subjected to transverse traction force, the iron tower deforms laterally
Can be decomposed by deformation of radar line of sight
The conversion formula of (1) is as follows:
wherein the content of the first and second substances,
is laterally deformed.
When the iron tower is a corner tower or the extension direction of the power transmission line has a corner, the deformation does not belong to the technical content of the invention and is not further elaborated.
The above-mentioned embodiments only express the embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.