CN111461918A - Power transmission line tree flashing hidden danger monitoring method based on satellite optical image - Google Patents
Power transmission line tree flashing hidden danger monitoring method based on satellite optical image Download PDFInfo
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Abstract
The invention discloses a method for monitoring a potential hazard of tree flash of a power transmission line based on a satellite optical image, which utilizes satellite optical image data and data, takes a crown line distance, a tree line distance and a tree height as evaluation indexes of the potential hazard of the tree flash of the power transmission line, adopts a mark control watershed algorithm to extract the size of a crown and a maximum likelihood method to extract the power transmission line, and provides a crown line and tree line shortest distance calculation method based on a tree height and shortest distance method of a distance compensation method, so that the potential hazard of the tree flash fault of the power transmission line is monitored, identified and evaluated.
Description
Technical Field
The invention belongs to the technical field of power transmission line natural disaster fault monitoring, and particularly relates to a power transmission line tree flashing hidden danger monitoring method based on satellite optical images.
Background
Along with the increase of the scale of the power grid, the probability of the tree flash accident of the power transmission line in the thunderstorm weather is increased. In the natural disaster accidents of the power transmission line, the lightning disaster accidents account for more than 70 percent; the tree flashover may cause the outage of the power transmission line due to protection tripping, and the sudden tripping of the power transmission line also threatens the safe and stable operation of a large-scale power grid, influences the life of people and brings huge economic loss to production. Therefore, if the hidden danger of the tree flash fault can be found in time, the operation and inspection personnel can be arranged in time to process, and the loss can be reduced to the minimum.
At present, the power transmission line inspection still mainly depends on manual inspection and manual recording, and has the defects of high cost, dangerous working conditions, inspection loss and the like, and is difficult to operate and maintain and high in working strength. In recent years, aerial inspection is adopted, and the detection efficiency and the detection precision are improved. But aviation inspection is limited by factors such as flight safety, aviation control, weather changes and refueling. The development of satellite technology provides a new means for monitoring the tree flash of the transmission line, and compared with manual and aviation polling, the satellite polling has the advantages of short period, no potential safety hazard, wider polling coverage area, high response speed and the like. At present, satellite optical images are applied to the forest management fields of tree crown segmentation, tree height calculation and the like, but the monitoring of the hidden danger of the tree flash of the power transmission line is rarely researched and related.
Disclosure of Invention
The tree flash accident is related to parameter indexes such as the distance between a tree and a crown line of a power transmission line, the distance between the tree and the crown line, the height of the tree and the like, the tree grows fast, the crown is close to the power transmission line, and the tree flash fault is likely to occur, so that the power transmission line is tripped or shut down, the safe and stable operation of a power system is threatened, and huge loss is brought to the life and production of people. Because the tree flash fault hidden danger and the accident risk are in direct proportion to parameter indexes such as the crown line distance, the tree height and the like of the power transmission line, the tree flash fault hidden danger of the power transmission line can be judged according to the data indexes, and the tree flash fault hidden danger can be timely found and judged by monitoring the data indexes. The invention provides a method for extracting and judging the size of a tree crown based on a mark control watershed algorithm based on remote sensing satellite optical image data and data, and respectively calculating the height of a tree, the edge of the tree crown and the shortest distance from the top of the tree to a power transmission line based on a tree height compensation method and a shortest distance algorithm, thereby realizing the identification and judgment of the hidden danger of the tree flash fault of the power transmission line. Based on satellite optical image data and data, the tree flash fault hidden danger of the power transmission line is identified and monitored, and the method has the advantages of short inspection period, no potential safety hazard, wide inspection coverage area, high response speed and the like.
In order to achieve the above purposes, the technical scheme adopted by the invention is as follows:
the method utilizes satellite optical image data and data, takes the crown line distance, the tree line distance and the tree height as evaluation indexes of the tree flash hidden danger of the power transmission line, adopts a mark control watershed algorithm to extract the size of a crown and a maximum likelihood method to extract the power transmission line, provides a crown line and tree line shortest distance calculation method based on the tree height and shortest distance method of a distance compensation method, and monitors, identifies and evaluates the tree flash fault hidden danger of the power transmission line.
A method for monitoring a power transmission line tree flashing hidden danger based on a satellite optical image comprises the following steps:
1) analyzing 4 wave bands of the satellite image by using an optimal exponential method (OIF), wherein the 1 wave band, the 2 wave band, the 3 wave band and the 4 wave band respectively correspond to the following components: blue light wave band, green glow wave band, ruddiness wave band and near-infrared wave band, 4 wave bands have four kinds of wave band combinations, do respectively: 1. 2,3 wave bands, 1,2, 4 wave bands, 1, 3, 4 wave bands, 2,3, 4 wave bands, respectively calculating indexes of wave band combinations, selecting the wave band combination with the maximum index as an experimental wave band, then generating a false color image of the experimental wave band by using ENVI software, performing normalized vegetation index processing and mask processing on the false color image, and segmenting a crown region image by morphological filtering and a watershed marking algorithm;
2) roughly classifying the power transmission line images in the satellite images by using a maximum likelihood method, and manually classifying the classified power transmission line images in an ENVI class for the second time to obtain power transmission line images;
3) intercepting a tree satellite picture in a satellite image, then introducing the tree satellite picture into Sketch Up software, constructing a circumscribed rectangle of the tree satellite picture in the tree satellite picture, setting the time and the place of the tree satellite picture in the Sketch Up software, adjusting the height of the circumscribed rectangle to establish a three-dimensional model of the tree outline circumscribed rectangle, enabling the shadow highest point of the three-dimensional model to coincide with the shadow highest point of the tree satellite picture, measuring the height of the three-dimensional model, obtaining a pseudo-tree height through proportion conversion, and then calculating by adopting a distance compensation method to obtain the compensated and corrected tree height;
4) synthesizing the crown area image obtained in the step 1) and the power transmission line image obtained in the step 2), determining the shortest distance from a tree to a power transmission line by adopting a circular search method and determining the shortest distance from the power transmission line to the edge of the crown by adopting a strip area search method according to the synthesized images of the crown area image and the power transmission line image;
5) according to the shortest distance from the tree to the power transmission line and the shortest distance from the power transmission line to the edge of the crown, obtained in the step 4), the early warning of the hidden danger of the tree flash of the power transmission line is divided into: the danger is extreme, and the tree obstacles are urgently needed to be removed; in case of moderate danger, the tree obstacle needs to be removed recently; safety, no attention is needed in the near term; thereby giving an early warning strategy.
On the basis of the scheme, the calculation formula of the index of the waveband combination in the step 1) is as follows:
wherein OIF is the index of the band combination, SiFor the standard deviation of the ith band in the band combination, i is 1,2,3, RjkIs the correlation coefficient between different bands in the band combination, and r is the combination number of different bands in the band combination.
On the basis of the above scheme, the specific process of calculating the compensated and corrected tree height by using the distance compensation method in step 3) is as follows:
the real shadow length of the tree is I1+XLUsing the height h of the three-dimensional modelmCalculating the shadow length I of the three-dimensional model according to the sun altitude α1Obtaining the compensation distance X according to the distance from the center of the crown to the edge of the crownLAnd then using trigonometric function to calculate and obtain real tree height H of treesThe calculation formula is as follows:
(deg)＝0.006918-0.399912cos(b)+0.070257sin(b)-0.006758cos(2b)
+0.000907sin(2b)-0.002697cos(3b)+0.00148sin(3b) (4)
t ═ × 15 ° (5) (true suntime-12)
True solar time equal to the mean time plus true solar time difference (6)
I1＝hm/tan(α) (7)
Hs＝(I1+XL)×tan(α) (8)
Wherein α is the solar altitude,
the satellite image acquisition method comprises the steps of representing solar declination for geographical latitude, representing a solar declination, wherein t represents a time angle, b represents the angle of the earth revolution from 1 month and 1 day to the calculation day, the calculation formula is that b is 2 × pi × (day-1)/365, day represents the number of days from 1 month and 1 day to the calculation day each year, pi represents a circumferential rate, deg represents an angle, true solar time is a time system established according to true solar day, mean solar time is Beijing time, the true solar time difference is time difference between a satellite image acquisition place and Beijing time by taking Beijing time as a standard rod, and I is the time difference between the satellite image acquisition place and the Beijing time1Is the shadow length, h, of the three-dimensional modelmIs the height of the three-dimensional model, HsIs the true height, X, of the treeLTo compensate for the distance.
On the basis of the above scheme, the specific process of the circular ring search method in step 4) is as follows:
firstly, preprocessing the tree crown edges and the power transmission lines, and distinguishing different tree crowns and power transmission lines by setting different gray values for different tree crown edges and power transmission linesThen with crown vertex O (x)0,y0) The edge point of the crown closest to the top of the crown is the radius rdMake a circle with radius rdIs in pixels, the equation for a circle is:
(x-x0)2+(y-y0)2＝rd 2(9)
with rd+1 as the new radius with crown vertex O (x)0,y0) Continuing to make a circle as the center of the circle, the equation of the circle is:
(x-x0)2+(y-y0)2＝(rd+1)2(10)
the part of a circular ring formed between the two circles is a search area which satisfies
rd 2<＝(x-x0)2+(y-y0)2<＝(rd+1)2(11)
If no point meeting the requirement exists in the search area, the radius of the inner circle and the outer circle is increased by 1 pixel, a new circular ring is formed for continuous search until a pixel point meeting the requirement is searched, and all pixel points meeting the requirement in the circular ring are subjected to distance operation with the center of the circle to obtain a distance (d)1,d2,...,dn) From which the minimum distance d is foundsAs minimum horizontal distance of tree line, dsThe unit of (a) is a pixel, and the calculation formula of the distance is as follows:
wherein (x)i‘,yi’) Is any point in the ring, wherein i' is 1,2i’The horizontal distance from the point to the top point of the crown;
minimizing the horizontal distance d of the tree line according to the resolution of the imagesConvert to the shortest horizontal distance D of real trees to the power transmission line, its unit is meter, and the conversion formula is:
D＝ds× resolution (13)
Tree to transmission of electricityThe shortest horizontal distance D of the line is combined with the height M of the transmission line and the real height H of the treesWhether the power transmission line is threatened or not when the tree is broken is calculated, and the calculation formula is as follows:
wherein S is the linear distance from the bottom end of the tree to the power transmission line and the unit is meter, W is the closest distance from the power transmission line when the tree is broken and the unit is meter, wherein the height M of the power transmission line and the real height H of the treesThe units of (A) are all meters.
On the basis of the scheme, the specific process of the bar region searching method in the step 4) is as follows:
according to the minimum horizontal distance d of the tree linesObtaining the distance crown vertex O (x) on the transmission line0，y0) Nearest point P1(x1，y1) The line segment OP can be obtained by the theorem of the shortest distance from point to straight line1Perpendicular to the power line L1，P1For the foot, according to the crown vertexes O and P1The coordinates of the points are taken to be line segments OP1Slope k of1The power line L is obtained from the product of the vertical slopes of two straight lines as-11Slope k of2Power line L1And a line segment OP1The equation of the straight line of (1) is:
will power line L1Along line segment OP1The direction is translated downwards by one pixel unit to obtain the slope k2Line L2Straight line L2And line segment OP1Meet at point P2Is provided with P2Has the coordinates of (x)2,y2) The minimum horizontal distance of the tree line is dsThus OP2Has a length of ds-1, adding P2The point coordinates are taken into formula (12) and formula (15), and are calculated as follows:
by P2Point coordinates and straight line L2To find a straight line L2Equation, will power line L1And line L2The bar-shaped area between the two is used as a search area, if no point meeting the requirement exists in the search area, the power line L is transmitted1And line L2All along OP1The direction is translated downwards by 1 pixel to form a new search area for continuous search until the pixel points meeting the requirements are searched for the first time, and all the pixel points meeting the requirements are calculated by using a point-to-straight line distance formula and the power transmission line L1The formula is as follows:
wherein U, V, G is the coefficient of the linear equation (x)s',ys') For any target point coordinate to be calculated, where s' ∈ [1, n]，fs'For any target point to be calculated to power line L1Finding out the minimum distance among all distances to obtain the minimum distance F from the power transmission line to the crown edge, wherein the unit of the minimum distance F is a pixel, and multiplying the minimum distance F from the power transmission line to the crown edge by the resolution ratio to obtain the actual shortest horizontal distance F from the power transmission line to the crown edgesIn meters.
On the basis of the scheme, the specific process of the step 5) is as follows:
the position relation of trees and power transmission lines is divided into two types:
(1) when trees are below the power transmission line, whether the power transmission line is threatened by the trees or not, and the height M of the power transmission line and the true height H of the treess(ii) related;
a)M-Hs<9, issuing a first-level early warning when the vehicle is extremely dangerous;
b)9<M-Hs<12, issuing a secondary early warning when the danger is moderate;
c)M-Hs>12, safety, and no early warning is issued;
(2) when trees are arranged on two sides of the power transmission line, whether the power transmission line is threatened or not is higher than the reality of the treesDegree HsHeight M of power transmission line, shortest distance W from power transmission line when tree is broken and shortest horizontal distance F from power transmission line to crown edges(ii) related;
a)Fs<8.5 and Hs>When M-2 or W is less than or equal to 0, extreme danger is caused, and primary early warning is issued;
b)Fs>11.5 and W>3 or Hs<M-9, safety, no warning;
c) and (4) issuing a secondary early warning if the other conditions are moderate dangers.
Has the advantages that:
the monitoring method of the tree flash hidden danger of the power transmission line based on the satellite optical image utilizes the image with the resolution of 0.8 m of a high-resolution No. 2 satellite, and the result of case simulation calculation shows that the method has the following effects:
1) the algorithm for calculating the shortest distance between the trees and the power transmission line and the shortest distance between the edges of the tree crowns and the power transmission line can judge whether the power transmission line is threatened by the trees on two sides and below.
2) The method for dividing the tree crown and calculating the height of the building is applied to the extraction of the tree crown and the calculation of the tree height in the monitoring of the hidden danger of the tree flash of the power transmission line, and the monitoring and calculating processes of the tree height compensation method are added.
3) The construction comprises the procedures of crown segmentation, transmission line segmentation, tree height calculation, tree line distance, crown line distance and early warning criterion tree flash hidden danger monitoring, and monitoring of the tree flash hidden danger of the transmission line can be realized.
4) The result of typical case calculation shows that the accuracy of the monitoring method for the tree flash hidden danger can reach the level of 82.69 percent, and the method can be used for satellite inspection monitoring of the tree flash hidden danger of the power transmission line.
5) Although the accuracy of monitoring the hidden danger of the power transmission line tree by the satellite still needs to be improved, compared with aviation polling and monitoring, the method has the advantages of short period, no potential safety hazard, wider polling coverage area and the like.
Drawings
Fig. 1 tree height compensation principle.
Fig. 2 tree vertex search principle.
Fig. 3 the principle of coronal distance search.
Fig. 4 is a flow chart of a power transmission line tree flashing hazard monitoring method based on satellite optical images.
Detailed Description
The present invention will be described more fully in detail with reference to the accompanying figures 1-4.
According to a flow chart of a monitoring method for the hidden danger of tree flashing of the power transmission line shown in FIG. 4, the specific implementation modes of the technologies of image segmentation, tree height calculation, distance algorithm between trees and the power transmission line, early warning criterion and the like are as follows.
1) Image segmentation
The satellite images used have 4 bands of red, green, blue and near infrared, and in order to reduce the data processing amount, correlation analysis is performed first, and 3 bands with the largest information content are selected as experimental bands by an optimal Index method (OIF). The calculation formula of OIF is:
wherein OIF is the index of the band combination, SiIs the standard deviation, R, of the ith band in the band combinationjkIs the correlation coefficient between different bands in the band combination, and r is the combination number of different bands in the band combination.
The correlation coefficient and covariance between the image bands were calculated by the ENVI software, and the calculation results are shown in Table 1.
TABLE 1 correlation coefficient and covariance of each band
| | Band | 1 | Band 2 | Band 3 | Band 4 |
| |
1.000000 | 0.993261 | 0.990752 | 0.759142 | |
| Band 2 | 0.993261 | 1.000000 | 0.986537 | 0.816912 | |
| Band 3 | 0.990752 | 0.986537 | 1.000000 | 0.749464 | |
| Band 4 | 0.759142 | 0.816912 | 0.749464 | 1.000000 | |
| | Band | 1 | Band 2 | Band 3 | Band 4 |
| |
2560.926532 | 3172.649500 | 4168.986695 | 3228.762659 | |
| Band 2 | 3172.649500 | 3984.012354 | 5177.744817 | 4333.614357 | |
| Band 3 | 4168.986695 | 5177.744817 | 6914.075962 | 5237.600634 | |
| Band 4 | 3228.762659 | 4333.614357 | 5237.600634 | 7063.651733 |
The combination form of the 4 wave bands is as follows: 1. 2,3 wave bands; 1. 2, 4 wave bands; 1. 3, 4 wave bands; 2. and 3, and 4, substituting the data in the table 1 into the formula (1) to calculate the OIF, wherein the calculation result is shown in the table 2.
TABLE 2 OIF calculation results
| |
1，2，3 | 1，2，4 | 1，3，4 | 2，3，4 |
| Correlation coefficient | 2.97055 | 2.569315 | 2.499358 | 2.552913 |
| Standard deviation of | 13459.01 | 13608.59 | 16538.65 | 17961.74 |
| OIF | 4530.816 | 5296.583 | 6617.161 | 7035.782 |
As can be seen from table 2, the OIF values of bands 2,3, and 4 are the maximum, i.e., the optimal band combination. And synthesizing the 2,3 and 4 wave bands into a standard false color image according to the sequence of 4, 3 and 2. In order to further highlight the background of the crown and remove the background, normalized vegetation index (NDVI) processing is performed on the standard false color image, and the standard calculation formula of the NDVI is as follows:
wherein NDVI is normalized vegetation index, NIR is near infrared band reflectivity, RbThe reflectances of the red light bands respectively correspond to the two bands with the lowest correlation in the band combination, i.e., band 4 and band 3.
Setting a threshold value to classify the NDVI result II, taking the classified image as a mask to perform mask processing on the false color image, and performing morphological filtering on the processed image. The top of the crown is subjected to the strongest solar radiation, the pixel reflectivity is larger, the top of the tree is a local maximum point of the crown area, and the top of the tree is used as a foreground mark; at this time, the background of the image is black, so that the point with the pixel value of 0 is a background mark, and the tree crown area is segmented by a watershed algorithm.
And marking and classifying ground objects such as power transmission lines, tree crowns, lands and the like in the images by using ENVI software, wherein the classified images have a small number of wrong scores and need to be manually modified in the ENVI Classic software, namely, the regions of the power transmission lines are marked again and the power transmission lines are extracted.
2) Tree height calculation
The Sketch Up software has the function of simulating the sun and lamplight, can enable an object to generate a corresponding shadow at a certain set time and place, introduces a satellite picture, constructs a circumscribed rectangle of a tree in the image, sets the time and place of the picture in the software, adjusts the height of the circumscribed rectangle to establish a three-dimensional model, enables the highest point of the model shadow to coincide with the highest point of the tree shadow, measures the height of the three-dimensional model and obtains the height of a pseudo tree through proportional conversion.
The pseudo tree height needs to be subjected to distance compensation processing to obtain the correct tree height, as shown in fig. 1, when the shadow farthest point of the three-dimensional model reaches the point Z, the obtained height of the three-dimensional model is the tree height, the tree shadow farthest point Q is known in actual operation, the shadow of the three-dimensional model is overlapped with the tree shadow farthest point Q, and the obtained model height hmLess than the true height H of the treesThe height of the tree needs to be compensated, so that the real tree height is obtained, and the compensation principle is shown in figure 1.
The real shadow length of the tree is (I)1+XL) Using the height h of the modelmAnd the sun altitude α can calculate the shadow length I of the model1According to the distance from the center of the crown to the edge of the crownThe compensation distance X can be obtainedLThen, the real tree height can be calculated by using a trigonometric function, and the specific process is as follows:
(deg)＝0.006918-0.399912cos(b)+0.070257sin(b)-0.006758cos(2b)
+0.000907sin(2b)-0.002697cos(3b)+0.00148sin(3b) (4)
t ═ × 15 ° (5) (true suntime-12)
True solar time equal to the mean time plus true solar time difference (6)
I1＝hm/tan(α) (7)
Hs＝(I1+XL)×tan(α) (8)
Wherein α is the solar altitude,
the sun declination is represented by geographical latitude, t represents a time angle, b represents the angle of the earth revolution from 1 month and 1 day to the calculation day, the calculation formula is that b is 2 × pi × (day-1)/365, day represents the days from 1 month and 1 day to the calculation day each year, pi represents a circumference rate, deg represents an angle, true solar time is a time system established according to true solar day, average solar time is Beijing time, the true solar time difference is the time difference between the ground and Beijing time calculated by taking Beijing time as a benchmark, I1Is the length of the model shadow, hmIs the model height; hsIs the true height, X, of the treeLTo compensate for the distance.
And based on the extracted synthetic graph of the crown and the power transmission line, providing a shortest distance algorithm for searching the power transmission line by using the circular ring at the top of the tree and a shortest distance algorithm for searching the crown by using the mobile power transmission line.
3) Tree and power transmission line distance algorithm
The schematic diagram of the algorithm of the horizontal distance from the bottom end of the tree to the transmission line is shown in fig. 2. The method comprises the steps of preprocessing the tree crown edges and the power transmission lines, and setting different gray values for the different tree crown edges and the power transmission linesDifferent tree crowns and power transmission lines are obtained. Then using crown top point O (x)0,y0) As the circle center, the nearest crown edge point to the crown is the radius rd(unit: pixel) make a circle, the equation for the circle is:
(x-x0)2+(y-y0)2＝rd 2(9)
with (r)d+1) (unit: pixel) as a new radius, continuing to make a circle with the crown vertex as the center of the circle, and the equation is:
(x-x0)2+(y-y0)2＝(rd+1)2(10)
the part of a circular ring formed between the two circles is a search area which satisfies
rd 2<＝(x-x0)2+(y-y0)2<＝(rd+1)2(11)
If no point meeting the requirement exists in the search area, the radius of the inner circle and the radius of the outer circle are increased by 1 pixel to form a new circular ring for continuous search until a pixel point meeting the requirement is searched. All the pixel points which meet the requirement in the ring and the circle center (x)0,y0) Calculating the distance to obtain the distance (d)1,d2,...,dn) From which the minimum distance d is founds(unit: pixel) as the minimum horizontal distance of the tree line. The distance formula is:
wherein (x)i‘,yi’) Is any point in the ring, wherein i' is 1,2i’Is the horizontal distance from the point to the top of the tree.
The shortest distance d to be calculated according to the resolution of the imagesAnd converting into the shortest distance D (unit: meter) from the actual tree to the transmission line, wherein the conversion formula is as follows:
D＝ds× resolution (13)
Shortest distance D from tree to power transmission line is combined with defeatedHeight M (unit: meter) of electric wire and real height H of trees(unit: meter), can calculate whether will cause the threat to the power transmission line when trees break, the computational formula is:
wherein S is the linear distance (unit: meter) from the bottom end of the tree to the power transmission line, and W is the closest distance (unit: meter) from the power transmission line when the tree is broken.
The algorithm uses the circular ring as a search area, so that all pixel points cannot be traversed repeatedly.
4) Crown and power transmission line distance algorithm
The crown edge point closest to the power transmission line needs to be accurately found out for calculating the crown distance, the calculation is complex and time-consuming if the distances between the edge points and the power transmission line are calculated one by one, and in order to reduce the calculation time and accurately obtain the crown distance, a method for searching the crown edge point by using the mobile power transmission line is provided, and a schematic diagram is shown in fig. 3.
According to the minimum horizontal distance d of the tree linesObtaining the distance crown vertex O (x) on the transmission line0，y0) Nearest point P1(x1，y1) The line segment OP can be obtained by the theorem of the shortest distance from point to straight line1Perpendicular to the power line L1，P1Is a drop foot. According to O point and P1The coordinates of the points may be taken as a line segment OP1Slope k of1Power line L is obtained from the product of the vertical slopes of two lines as-11Slope k of2Power line L1And a line segment OP1The equation of the straight line of (1) is:
will power line L1Along line segment OP1The direction is translated downwards by one pixel unit to obtain the slope k2Line L2Straight line L2And line segment OP1Meet at point P2Is provided with P2Has the coordinates of (x)2,y2) Tree ofLine minimum horizontal distance ds(unit: pixel) and thus OP2Has a length of (d)s-1) (unit: pixel) will P2The point coordinates are taken into equations (12) and (15) and calculated as:
by P2Point coordinates and straight line L2To find a straight line L2Equation will power line L1And line L2The bar-shaped area between them is used as the search area, if there is no point meeting the requirement in the search area, the power line L1And line L2All along OP1The direction is translated downwards by 1 pixel to form a new search area for continuous search until a pixel point meeting the requirement is searched for the first time, as shown by a curve JK in FIG. 3, all pixel points meeting the requirement are calculated by using a point-to-straight line distance formula and are connected with a power transmission line L1The formula is as follows:
wherein U, V, G is the coefficient of the linear equation (x)s',ys') For any target point coordinate to be calculated, where s' ∈ [1, n]，fs'For any target point to be calculated to power line L1The minimum distance of all the distances is the minimum distance F (unit: pixel) from the power line to the crown edge, and the minimum distance F from the power line to the crown edge is multiplied by the resolution ratio to obtain the actual shortest horizontal distance F from the power line to the crown edges(unit: meter).
5) Early warning criterion
The early warning relation of trees and transmission lines is divided into three types: (1) the danger is extreme, and the tree obstacles are urgently needed to be removed; (2) in case of moderate danger, the tree obstacle needs to be removed recently; (3) safe and needs no attention in the near future.
According to the design specification of 110 kV-750 kV overhead transmission lines, the maximum windage yaw distance of 500kV transmission lines is 8.5 meters, the maximum sag distance is 9 meters, the safety distance to the ground is 11 meters, there are 28 insulators in total, each insulator is about 15 centimeters, therefore, the height from the ground of 500kV transmission lines is at least: 11+9+28 0.15 ═ 24.2 (units: m). The position relation of the trees and the power transmission line is divided into two types:
(1) when trees are below the power transmission line, whether the power transmission line is threatened by the trees or not, and the height M of the power transmission line and the true height H of the treess(ii) related;
a)M-Hs<9, issuing a first-level early warning when the vehicle is extremely dangerous;
b)9<M-Hs<12, issuing a secondary early warning when the danger is moderate;
c)M-Hs>12, safety and no early warning.
(2) When trees are arranged on two sides of the power transmission line, whether the power transmission line is threatened or not and the true height H of the treessHeight M of power transmission line, shortest distance W from power transmission line when tree is broken and shortest horizontal distance F from power transmission line to crown edgesAll have a relationship;
a)Fs<8.5 and Hs>When M-2 or W is less than or equal to 0, extreme danger is caused, and primary early warning is issued;
b)Fs>11.5 and W>3 or Hs<M-9, safety, no warning;
c) and (4) issuing a secondary early warning if the other conditions are moderate dangers.
And monitoring the hidden danger of the power transmission line tree according to the implementation mode and the flow of the figure 4.
Those not described in detail in this specification are within the skill of the art.
Claims (6)
1. A method for monitoring the hidden danger of the tree flash of a power transmission line based on a satellite optical image is characterized by comprising the following steps:
1) analyzing 4 wave bands of the satellite image by using an optimal exponential method, wherein the 1 wave band, the 2 wave band, the 3 wave band and the 4 wave band respectively correspond to each other: blue light wave band, green glow wave band, ruddiness wave band and near-infrared wave band, 4 wave bands have four kinds of wave band combinations, do respectively: 1. 2,3 wave bands, 1,2, 4 wave bands, 1, 3, 4 wave bands, 2,3, 4 wave bands, respectively calculating indexes of wave band combinations, selecting the wave band combination with the maximum index as an experimental wave band, then generating a false color image of the experimental wave band by using ENVI software, performing normalized vegetation index processing and mask processing on the false color image, and segmenting a crown region image by morphological filtering and a watershed marking algorithm;
2) roughly classifying the power transmission line images in the satellite images by using a maximum likelihood method, and manually classifying the classified power transmission line images in an ENVI class for the second time to obtain power transmission line images;
3) intercepting a tree satellite picture in a satellite image, then introducing the tree satellite picture into Sketch Up software, constructing a circumscribed rectangle of the tree satellite picture in the tree satellite picture, setting the time and the place of the tree satellite picture in the Sketch Up software, adjusting the height of the circumscribed rectangle to establish a three-dimensional model of the tree outline circumscribed rectangle, enabling the shadow highest point of the three-dimensional model to coincide with the shadow highest point of the tree satellite picture, measuring the height of the three-dimensional model, obtaining a pseudo-tree height through proportion conversion, and then calculating by adopting a distance compensation method to obtain the compensated and corrected tree height;
4) synthesizing the crown area image obtained in the step 1) and the power transmission line image obtained in the step 2), determining the shortest distance from a tree to a power transmission line by adopting a circular search method and determining the shortest distance from the power transmission line to the edge of the crown by adopting a strip area search method according to the synthesized images of the crown area image and the power transmission line image;
5) according to the shortest distance from the tree to the power transmission line and the shortest distance from the power transmission line to the edge of the crown, obtained in the step 4), the early warning of the hidden danger of the tree flash of the power transmission line is divided into: the danger is extreme, and the tree obstacles are urgently needed to be removed; in case of moderate danger, the tree obstacle needs to be removed recently; safety, no attention is needed in the near term; thereby giving an early warning strategy.
2. The method for monitoring the hidden danger of the power transmission line tree flashing based on the satellite optical image as claimed in claim 1, wherein the calculation formula of the index of the waveband combination in the step 1) is as follows:
wherein OIF is the index of the band combination, SiFor the standard deviation of the ith band in the band combination, i is 1,2,3, RjkIs the correlation coefficient between different bands in the band combination, and r is the combination number of different bands in the band combination.
3. The method for monitoring the hidden danger of the tree flash of the power transmission line based on the satellite optical image as claimed in claim 1, wherein the specific process of calculating the tree height after compensation and correction by adopting a distance compensation method in the step 3) is as follows:
the real shadow length of the tree is I1+XLUsing the height h of the three-dimensional modelmCalculating the shadow length I of the three-dimensional model according to the sun altitude α1Obtaining the compensation distance X according to the distance from the center of the crown to the edge of the crownLAnd then using trigonometric function to calculate and obtain real tree height H of treesThe calculation formula is as follows:
(deg)＝0.006918-0.399912cos(b)+0.070257sin(b)-0.006758cos(2b)+0.000907sin(2b)-0.002697cos(3b)+0.00148sin(3b) (4)
t ═ × 15 ° (5) (true suntime-12)
True solar time equal to the mean time plus true solar time difference (6)
I1＝hm/tan(α) (7)
Hs＝(I1+XL)×tan(α) (8)
Wherein α is the solar altitude,
the formula b is 2 × pi × (day-1)/365, day is 1 month and 1 day per year, and the calculation of the revolution angle of the earth is carried outCalculating the days of the day, wherein pi is the circumference ratio, and deg represents the angle; the real sun time is a time system established according to the real sun day; the plain solar time is the Beijing time; the real solar time difference is the time difference between the satellite image shooting place and the Beijing time by taking the Beijing time as a benchmark; i is1Is the shadow length, h, of the three-dimensional modelmIs the height of the three-dimensional model, HsIs the true height, X, of the treeLTo compensate for the distance.
4. The method for monitoring the hidden danger of the lightning strike of the power transmission line based on the satellite optical image as claimed in claim 3, wherein the specific process of the circular ring search method in the step 4) is as follows:
firstly, preprocessing the edges of the tree crowns and the power transmission lines, distinguishing different tree crowns and power transmission lines by setting different gray values for the edges of different tree crowns and the power transmission lines, and then using the top points O (x) of the tree crowns0,y0) The edge point of the crown closest to the top of the crown is the radius rdMake a circle with radius rdIs in pixels, the equation for a circle is:
(x-x0)2+(y-y0)2＝rd 2(9)
with rd+1 as the new radius with crown vertex O (x)0,y0) Continuing to make a circle as the center of the circle, the equation of the circle is:
(x-x0)2+(y-y0)2＝(rd+1)2(10)
the part of a circular ring formed between the two circles is a search area which satisfies
rd 2<＝(x-x0)2+(y-y0)2<＝(rd+1)2(11)
If no point meeting the requirement exists in the search area, the radius of the inner circle and the outer circle is increased by 1 pixel, a new circular ring is formed for continuous search until a pixel point meeting the requirement is searched, and all pixel points meeting the requirement in the circular ring are subjected to distance operation with the center of the circle to obtain a distance (d)1,d2,...,dn) FromTo find the minimum distance dsAs minimum horizontal distance of tree line, dsThe unit of (a) is a pixel, and the calculation formula of the distance is as follows:
wherein (x)i‘,yi’) Is any point in the ring, wherein i' is 1,2i’The horizontal distance from the point to the top point of the crown;
minimizing the horizontal distance d of the tree line according to the resolution of the imagesConvert to the shortest horizontal distance D of real trees to the power transmission line, its unit is meter, and the conversion formula is:
D＝ds× resolution (13)
The shortest horizontal distance D from the tree to the transmission line is combined with the height M of the transmission line and the real height H of the treesWhether the power transmission line is threatened or not when the tree is broken is calculated, and the calculation formula is as follows:
wherein S is the linear distance from the bottom end of the tree to the power transmission line and the unit is meter, W is the closest distance from the power transmission line when the tree is broken and the unit is meter, wherein the height M of the power transmission line and the real height H of the treesThe units of (A) are all meters.
5. The method for monitoring the hidden danger of the lightning strike of the power transmission line based on the satellite optical image as claimed in claim 4, wherein the specific process of the bar region search method in the step 4) is as follows:
according to the minimum horizontal distance d of the tree linesObtaining the distance crown vertex O (x) on the transmission line0，y0) Nearest point P1(x1，y1) The line segment OP is obtained by the theorem of the shortest distance from the point to the straight line1Perpendicular to the power line L1，P1For the foot, according to the crown vertexes O and P1Coordinates of pointsTo line segment OP1Slope k of1The power line L is obtained from the product of the vertical slopes of two straight lines as-11Slope k of2Power line L1And a line segment OP1The equation of the straight line of (1) is:
will power line L1Along line segment OP1The direction is translated downwards by one pixel unit to obtain the slope k2Line L2Straight line L2And line segment OP1Meet at point P2Is provided with P2Has the coordinates of (x)2,y2) The minimum horizontal distance of the tree line is dsThus OP2Has a length of ds-1, adding P2The point coordinates are taken into formula (12) and formula (15), and are calculated as follows:
by P2Point coordinates and straight line L2To find a straight line L2Equation, will power line L1And line L2The bar-shaped area between the two is used as a search area, if no point meeting the requirement exists in the search area, the power line L is transmitted1And line L2All along OP1The direction is translated downwards by 1 pixel to form a new search area for continuous search until the pixel points meeting the requirements are searched for the first time, and all the pixel points meeting the requirements are calculated by using a point-to-straight line distance formula and the power transmission line L1The formula is as follows:
wherein U, V, G is the coefficient of the linear equation (x)s',ys') For any target point coordinate to be calculated, where s' ∈ [1, n]，fs'For any target point to be calculated to power line L1Finding the minimum of all distancesThe minimum distance F from the power transmission line to the crown edge is obtained, the unit of the minimum distance F is a pixel, and the minimum distance F from the power transmission line to the crown edge is multiplied by the resolution ratio to obtain the actual shortest horizontal distance F from the power transmission line to the crown edgesIn meters.
6. The method for monitoring the hidden danger of the power transmission line tree flashing based on the satellite optical image as claimed in claim 5, wherein the specific process of the step 5) is as follows:
the position relation of trees and power transmission lines is divided into two types:
(1) when trees are below the power transmission line, whether the power transmission line is threatened by the trees or not, and the height M of the power transmission line and the true height H of the treess(ii) related;
a)M-Hs<9, issuing a first-level early warning when the vehicle is extremely dangerous;
b)9<M-Hs<12, issuing a secondary early warning when the danger is moderate;
c)M-Hs>12, safety, and no early warning is issued;
(2) when trees are arranged on two sides of the power transmission line, whether the power transmission line is threatened or not and the true height H of the treessHeight M of power transmission line, shortest distance W from power transmission line when tree is broken and shortest horizontal distance F from power transmission line to crown edges(ii) related;
a)Fs<8.5 and Hs>When M-2 or W is less than or equal to 0, extreme danger is caused, and primary early warning is issued;
b)Fs>11.5 and W>3 or Hs<M-9, safety, no warning;
c) and (4) issuing a secondary early warning if the other conditions are moderate dangers.
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