CN103675814B - The method of buildings ground level height is determined based on circumference SAR - Google Patents
The method of buildings ground level height is determined based on circumference SAR Download PDFInfo
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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
- 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
- G01S13/904—SAR modes
- G01S13/9088—Circular SAR [CSAR, C-SAR]
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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
- 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
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- 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
- G01S13/9023—SAR image post-processing techniques combined with interferometric techniques
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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
- G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
- G01S7/539—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
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Abstract
The invention provides a kind of method determining buildings ground level height based on circumference SAR.The method comprises: steps A, and rough estimate goes out target structures thing ground level height H
0; Step B, selects with H
0centered by areas imaging, in this areas imaging, divide multiple height layer, for each height layer, circumference SAR imaging carried out respectively to buildings; Step C, after several height layer circumference SAR imaging in image, selects rescattering bright line to form closed region and a disjoint sub-picture; And step D, rescattering bright line is formed closed region and the height of height layer corresponding to disjoint image is defined as the bottom level of target structures thing.The present invention is based on circumference SAR and determine that the method for buildings ground level height utilizes circumference SAR to the advantage of the omnibearing observation of target, accurately can draw the elevation information on construction bottom ground.
Description
Technical Field
The invention relates to a building ground level height determining method and a contour imaging method based on a circumference SAR. Wherein, the ground level of the building refers to the ground around the building. And the height of the ground level of the building refers to the height of the sea wave on the ground around the building.
Background
Synthetic Aperture Radars (SAR) are widely used in the field of remote sensing. In SAR images, typical urban structures are affected by eclipse, secondary reflection and shadowing due to the slant range imaging characteristics of radar sensors. The secondary reflection effect is an important characteristic in the SAR image of the building, the secondary reflection indicates that the building exists, the position of the secondary reflection effect is opposite to a side wall body of the building, and the secondary reflection effect can be used as an important characteristic for detecting and reconstructing the building through the SAR (1NSAR) signal. However, the secondary reflection effect depends on the height of the building (the higher the building the stronger the secondary reflection and vice versa) and the azimuth angle(angle between building wall and sensor orientation). If the building wall is parallel to the flying direction of the sensor or the included angle is less than 10 degrees, the backscattering is extremely strong (the backscattering effect has very strong reflected signals when the wall on the side of the building facing the sensor is almost parallel to the SAR azimuth direction, in addition, the backscattering intensity is rapidly attenuated in the range with a small azimuth angle, and the attenuation is slowed down in the place with a large azimuth angle), for the traditional method for imaging the building by adopting the linear SAR, if the sensing method is adopted, the backscattering effect is extremely strongThe included angle between the flight direction of the device and the wall surface of the building is large, so that the secondary scattering effect is not obvious. Because the azimuth angles of the buildings on the SAR image are different, the technology of detecting the buildings based on the secondary reflection effect by using the linear SAR has limitations.
In the case of the circular SAR, all buildings can be observed by 360 degrees (except for the sheltered buildings), so that each wall surface outside the buildings can generate a strong secondary scattering effect, which is very beneficial to the acquisition of the contour information of the buildings. The building is imaged by using the circular SAR, and if an imaging plane is arranged at the bottom of the building, a bright line formed by the secondary scattering effect forms a closed polygonal line frame, so that the position and area information of the building can be accurately obtained. However, in the actual circular SAR imaging process, without the aid of auxiliary elevation information (such as DEM, DSM obtained by INSAR or Lidar), it is possible to set the imaging plane at other heights because the exact height of the ground plane of the building is not known, so that the bright lines generated by the dihedral effect may be shifted from their true positions. The wall surface outside the building has strong directivity of secondary scattering with the ground, so when the imaging height is different from the building bottom height, the position of a bright line generated by the secondary scattering moves along the direction vertical to the wall surface. In addition, for example, the DEM and the DSM are obtained through the INSAR or the Lidar, the elevation data obtained by the Lidar has high accuracy, but the discrete elevation points are not beneficial to accurately positioning the sides of the building and have high acquisition cost; the INSAR can acquire continuous ground elevation information, but for buildings, some technical problems of the SAR image such as shadow and overlapping are not easy to solve, so that INSAR measurement is influenced.
In the process of implementing the present invention, the applicant finds that the method for determining the height of the ground plane of the building in the prior art needs to obtain accurate elevation information of the building area by auxiliary means such as an interferometric SAR (insar) or an airborne lidar (lightdetectionandranging), and meanwhile, the stereo measurement method based on the circumferential SAR data has a height measurement accuracy of more than 2m and a limited accuracy.
Disclosure of Invention
Technical problem to be solved
In view of the above technical problem, the present invention provides a method for determining the height of the ground level of a building based on a circular SAR.
(II) technical scheme
According to one aspect of the invention, a method for determining the ground level height of a building based on a circumferential SAR is provided. The method comprises the following steps: step A, roughly estimating the height H of the ground level of a target building0(ii) a Step B, selecting H0Dividing a plurality of height layers in the imaging range which is used as a central imaging range, and respectively carrying out circumferential SAR imaging on the building aiming at each height layer; step C, selecting a secondary scattering bright line to form a closed region and a non-intersected sub-image in the images after the multiple height layer circumference SAR imaging; and step D, determining the height of the height layer corresponding to the image of which the secondary scattering bright lines form the closed area and are not intersected as the bottom height of the target building.
(III) advantageous effects
According to the technical scheme, the method for determining the ground level height of the building based on the circumferential SAR utilizes the advantage of the circumferential SAR in omnibearing observation of the target, does not need auxiliary means, and can obtain the elevation information of the ground at the bottom of the building only by judging whether the secondary scattering bright lines formed by each outer wall of the building and the ground form a closed polygon or not from the circumferential SAR image.
Drawings
Fig. 1 shows the relationship between the position of a secondary scatter bright line in a circumferential SAR image and the height of an imaging plane;
2a-2c show the position of a bright line in an image reflecting the two-dimensional outline of a building when the imaging plane is coincident with the ground level of the building, below the ground level of the building, and above the ground level of the building, respectively;
FIG. 3 is a flow chart of a method for determining the ground level height of a building based on a circumferential SAR in accordance with an embodiment of the present invention;
fig. 4 is a schematic diagram of determining a connected area of the first mark point in step C of the method shown in fig. 3.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and the accompanying drawings. It should be noted that in the drawings or description, the same drawing reference numerals are used for similar or identical parts. Implementations not depicted or described in the drawings are of a form known to those of ordinary skill in the art. Additionally, while exemplifications of parameters including particular values may be provided herein, it is to be understood that the parameters need not be exactly equal to the respective values, but may be approximated to the respective values within acceptable error margins or design constraints. Directional phrases used in the embodiments, such as "upper," "lower," "front," "rear," "left," "right," and the like, refer only to the orientation of the figure. Accordingly, the directional terminology used is intended to be in the nature of words of description rather than of limitation.
Aiming at the limitation of the imaging technology based on the linear SAR in the prior art, the invention provides that the building can be imaged by using the circular SAR imaging technology. In the case of the circular SAR, all buildings can be observed by 360 degrees (except for the sheltered buildings), so that each wall surface of the building can generate a strong secondary scattering effect, which is very beneficial to building detection and reconstruction. When the building is imaged by using the circular SAR, if the imaging plane is arranged at the bottom of the building, the bright line formed by the secondary scattering effect forms a closed figure (such as a rectangle), so that the position and area information of the building can be accurately obtained. However, in the actual circular SAR imaging process, the exact height of the ground plane of the building is not clear, and it is possible to set the imaging plane at other heights, so that the bright lines generated by the dihedral effect may be shifted from their true positions. It should be noted here that if the scattering properties of the scatterers are isotropic (e.g., a jog ball), then if the imaging plane heights are not correct, then there is a possibility that the image will have side lobes in all directions. For a building wall surface, the directionality of the secondary scattering effect is strong, so when the imaging height is different from the height of the ground plane of the building, the position of a bright line generated by the dihedral angle effect only moves along the direction vertical to the wall surface.
Fig. 1 shows the relationship between the position of a secondary scatter bright line in a circular SAR image and the height of the imaging plane. In fig. 1, O denotes a position (zero doppler position) of the radar detector, 0 is an incident angle of the radar detector, H is a vertical height of the radar detector from the ground, point a is an angle between a wall surface of a building and the ground, point B is an angle between the wall surface of the building and the ground detected when an imaging plane of a bottom surface of the building is lower than an actual plane, point C is an angle between the wall surface of the building and the ground detected when the imaging plane of the bottom surface of the building is higher than the actual plane, Δ H1Is the height difference, Δ h, between the imaging plane and the actual plane when the imaging plane is lower than the actual plane2Is the height difference between the imaging plane and the actual plane when the imaging plane is higher than the actual plane, X is the horizontal distance between the O point and the wall surface of the building, and Delta X1Is the horizontal distance between points A and B, Δ X2Is the horizontal distance between points a and C.
Referring to fig. 1, since | OA | ═ OB | > | OC |, it can be obtained
(H-Δh)2+(X+ΔX)2＝H2+X2(1)
Δ h > 0 (i.e., Δ h) when the imaging plane is higher than the actual plane height2) Δ X > 0 (i.e., Δ X)2) Namely, the bright line translates inwards along the normal direction of the wall surface, and the translation amount is in direct proportion to delta h; Δ h < 0 (i.e., Δ h) when the imaging plane is below the actual plane height1)，ΔX＜0(ΔX1) I.e. the bright line is translated outwards along the wall surface normal direction. If the imaging plane is set at the ground level of the building, as shown in FIG. 2a, the radar detector is observed at 360 degrees, and the radar is reflected by the second reflectionThe generated bright lines are closed, and two-dimensional position and outline information of the building can be accurately obtained according to a rectangular wire frame formed by the bright lines (the building is assumed to be rectangular along the section of the height). When the imaging plane is lower than the building plane, the bright line will translate outward along the normal of the wall surface, as shown in fig. 2b, and the bright line will spread around and no longer close. When the imaging plane is above the building plane, the bright lines are translated inward along the wall surface normal direction, and the bright lines are crossed as shown in fig. 2 c.
According to the secondary reflection characteristic of the circumferential SAR building wall surface, in the actual imaging process, under the condition that a Digital Elevation Model (DEM) of a building is unknown, whether the imaging height is consistent with the bottom surface or not can be judged according to whether a secondary reflection bright line of the building wall surface is closed or not, and meanwhile, the specific position and the floor area of the building can be determined. Based on the characteristic that the amplitude value of the secondary reflection bright line is most remarkable in the scattering characteristic of the building, the embodiment of the invention provides a circular SAR building imaging method.
Fig. 3 is a flowchart of a method for determining the height of the ground level of a building based on a circular SAR according to an embodiment of the present invention. As shown in fig. 3, according to an embodiment of the present invention, there is provided a method for determining a ground level height of a building based on a circular Synthetic Aperture Radar (SAR), the method including:
step A, roughly estimating the height H of the ground level of a target building0；
In this step, the height H of the ground level of the target building is roughly estimated0The bottom height of the target building may be initially estimated using methods known in the art, such as: roughly estimating the bottom height of the target building by using the multi-angle observation geometry of the circular track SAR and adopting a stereo measurement method, namely: dividing a 360-degree radar platform track circular ring into a plurality of sections of circular arcs, dividing each section of circular arc into a plurality of sub-apertures, searching pixel points matched with a central image on other sub-aperture images by utilizing the similarity between sub-aperture images and the maximum correlation coefficient method to obtain the position offset of the pixel points and the central image, and further extracting a ground fieldDigital elevation DEM of the scene, i.e. the ground level height H of the target building0. The specific steps of the method are detailed in the following reference 1: StephanPalm, Herley, Oriot, and Hubert M Cantaloube, RarargrammetricDEM extraction and Irurbanan area Using circular SARImagery [ D]IEEETRANSACTIONGEOSCIENCEPCEANDRETESENSING, vol.50, No.11, pp: 935 952, nov.2012. For the purpose of highlighting and simplifying the present application, well-known methods are not described in detail.
Step B, selecting the H0Dividing a plurality of height layers in the imaging range which is used as a central imaging range, and carrying out circumferential SAR imaging on the building aiming at each height layer;
in this step, the imaging range may be selected based on various factors, such as the roughly estimated height H of the ground level of the target building0To the accuracy of (2). For example, the H can be selected0For rough estimate of center height H0A range of 4 to 8 times the accuracy of the stereo measurement is adopted as the imaging range. Wherein the stereo measurement accuracy is related to the azimuth angle difference between the sub-aperture images used to extract the DEM and the registration accuracy between the sub-aperture images. The stereo measurement precision of different wave bands is different, and in the X wave band, the stereo measurement precision of the circumferential SAR can reach 1m-2 m; in the P wave band, 3m-5m can be achieved.
The height may be divided at intervals in the selected imaging range, resulting in a plurality of height layers. The interval delta h between two adjacent height layers can satisfyH represents the height between the radar detector and the ground, X represents the horizontal distance between the projection point of the radar detector on the ground and the target building, C represents the light speed, and B represents the emission bandwidth of the radar detector.
Step C, selecting a secondary scattering bright line to form a closed region and a non-intersected sub-image in the images after the multiple height layer circumference SAR imaging;
here, it is known to determine whether or not the secondary scattering bright lines in the image form a closed region and do not intersect each other. Further, a more typical method is presented herein, the method comprising:
and a substep C1 of obtaining a weight sum of the images after the circumferential SAR imaging of each height layer, wherein the step of obtaining an image weight sum comprises:
a sub-step C1a, defining the pixels with energy amplitude higher than a preset threshold value in the image as first mark points, and defining the pixels with energy amplitude lower than the preset threshold value in the image as second mark points;
in this sub-step, the predetermined threshold may be determined in a number of ways, for example, based on empirical values or typical values. The predetermined threshold may be determined, for example, using an everlasting false alarm CFAR detection. The CFAR method is a common method for detecting the strong scattering target on the SAR image, and is widely applied to the detection of the artificial target of the SAR image. The CFAR detection method is a pixel-level target detection method, and is characterized in that the gray level of a target pixel is higher than that of a background and has stronger contrast relative to the background, and the aim of detecting the target pixel is fulfilled by comparing the gray level of a single pixel with a certain threshold. The predetermined threshold is determined by the statistical characteristics of the clutter given the false alarm rate.
The general process of the CFAR method is: according to the statistical detection theory, under the condition of a given false alarm rate, firstly, a detection threshold value is obtained in a self-adaptive mode according to the statistical characteristics of the background clutter around the target, and then the pixel to be detected is compared with the self-adaptive threshold value to judge whether the pixel is the target point. Through the sliding of the reference window, the self-adaptive detection of all pixels is realized. The statistical properties of the background clutter around the target are typically determined by the pixels within a reference window around the target pixels.
A sub-step C1b of selecting at least one region of interest in the image, wherein the region of interest contains a certain number of said first marker points;
such a weighted sum is still meaningful if the number of regions of interest (or the number of second marker points) is different for each image. This is because we assign a weight to the second marker in the region of interest based on a certain rule, and the number of the second marker cannot determine the size of the weight.
The method for selecting the region of interest may adopt a method existing in the prior art, such as a marker extraction method, and the specific content thereof is described in reference 2 (high resolution SAR image building extraction method research [ D ], hunan, university of national defense science and technology research institute, 2009). Those skilled in the art will appreciate that the threshold determination method is exemplary and not limiting.
In an embodiment of the present invention, another method for selecting a region of interest is provided, wherein selecting a region of interest in an image may include:
in particular, in certain implementations, the image may be scanned using a window of pixels. The predefined size of the pixel window may be P × Q, P being selected from integer values in the range of 2-4 and Q being selected from integer values in the range of 2-4. For example, the size of the pixel window may be, for example, 2 × 2, 2 × 3, 2 × 4, 3 × 2, 3 × 3, 3 × 4, 4 × 2, 4 × 3, 4 × 4. Assuming that a pixel window is scanned to a certain area (the area size is equal to the pixel window size and may be referred to as a pixel window area), if a first marker is in the area, the pixel window is moved to a pixel window area adjacent to the area along a horizontal direction, a vertical direction and an diagonal direction respectively (the pixel window area and the adjacent window area may be edge-adjacent or angle-adjacent and do not overlap), if the first marker is in the adjacent pixel window area, the pixel window is moved to a next pixel window area adjacent to the adjacent pixel window area on the basis of the adjacent pixel window area; if there is no first marker in the adjacent pixel window area, the above-described moving process is not performed, and the pixel window is moved to another pixel window area adjacent to the pixel window area (for example, the pixel window area may have two adjacent pixel window areas in the horizontal direction, two adjacent pixel window areas in the vertical direction, and four adjacent pixel window areas in the diagonal direction) and the above-described operation is repeated.
After traversing the pixels of the image according to the above process, at least one first marker connected region can be obtained, as shown by the white region in fig. 4. And selecting the connected regions with the number of pixels larger than N (the value range of N can be 10-20) from the connected regions. And then, respectively enclosing the connected regions by using polygons with the smallest areas, and determining the enclosed regions as regions of interest.
A substep C1C, assigning weights to the second marker points in the region of interest based on a rule, wherein the rule includes assigning a higher weight to a second marker point if the second marker point is surrounded by the first marker point for four weeks; if a second marking point is partially surrounded by the first marking point, giving a lower weight to the second marking point; if only one side of a second marking point has the first marking point, giving a zero weight to the second marking point;
in this embodiment, the second mark point is weighted according to the following formula:
in formula 3, T (x)i,yj) Denotes SmIn the region of (x)i,yj) The weight of the second mark point at the position is usually selected from a1＝2，a2＝1。
A sub-step C1d of summing the weights of the second markers in the at least one region of interest in the image of each height layer, the weights being the sum of F (h)n) As shown in the following formula:
wherein: smAnd M represents the number of the first mark point connected areas of the nth layer image.
And a substep C2, selecting the image with the maximum weight and judging the image as an image in which the secondary scattering bright lines form a closed region and do not intersect.
It should be noted that, in this step, a line segment detection method may be used to select one image, which is formed by the twice-scattered bright lines and does not intersect with each other, from a plurality of height layer circular SAR imaged images, and the specific content thereof is described in reference 3(f.tupin, h.main, j. -f.mangin, j. -m.nicolas, and e.pecher, detection nonfluorinated emitting sarimages: application to network operation, "ieee transmission activity system center and detection state", vol.36, No.2, pp.434-453, and mark.1998.).
Step D, determining the height of the height layer corresponding to the image which is determined that the secondary scattering bright lines form a closed area and does not intersect with the closed area as the bottom height of the target building, namely as shown in the following formula:
wherein,representing the finally determined height, h, of the ground level of the buildingnThe height of the nth height layer is shown, and N is the number of height layers.
Up to this point, the present embodiment has been described in detail with reference to the accompanying drawings. From the above description, the person skilled in the art should have clear knowledge of the method for determining the height of the ground level of a building based on circumferential SAR according to the present invention.
Furthermore, the above definitions of the various elements and methods are not limited to the various specific structures, shapes or configurations mentioned in the embodiments, which may be readily substituted by those of ordinary skill in the art.
In summary, the invention utilizes the advantage of the circumferential SAR in omnibearing observation of the target, does not need auxiliary means, and can obtain the elevation information of the ground at the bottom of the building only by judging whether the secondary scattering bright lines formed by each outer wall of the building and the ground form a closed polygon or not from the circumferential SAR image.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for determining the height of the ground level of a building based on a circular SAR is characterized by comprising the following steps:
step A, roughly estimating the height H of the ground level of a target building0；
Step B, selecting the H0Dividing a plurality of height layers in an imaging range which is used as a center, and respectively carrying out circumferential SAR imaging on the building aiming at each height layer;
step C, selecting secondary scattering bright lines to form an image which is a closed area and does not intersect in the images after the multiple height layer circumference SAR imaging; and
and D, determining the height of a height layer corresponding to the image with the secondary scattering bright lines forming a closed area and without intersection as the bottom height of the target building.
2. The method according to claim 1, wherein the step C of selecting one image in which the secondary scattering bright lines form a closed region and do not intersect in the following manner from the plurality of images comprises:
and a substep C1 of obtaining a weight sum of the images after the circumferential SAR imaging of each height layer, wherein the step of obtaining the weight sum of an image comprises the following steps:
a sub-step C1a, defining the pixels with energy amplitude higher than a preset threshold value in the image as first mark points, and defining the pixels with energy amplitude lower than the preset threshold value in the image as second mark points;
a sub-step C1b of selecting at least one region of interest in the image, wherein the region of interest contains a certain number of said first marker points;
a sub-step C1C, assigning a weight to the second marker point in the region of interest based on a rule, wherein the rule includes:
if a second marking point is surrounded by the first marking point in four weeks, giving a higher weight to the second marking point;
if a second marking point is partially surrounded by the first marking point, giving a lower weight to the second marking point;
if only one side of a second marking point has the first marking point, giving a zero weight to the second marking point;
a sub-step C1d of summing the weights of the second marker points in at least one region of interest in the image of each height layer;
and a substep C2, selecting the image with the maximum weight and judging the image as an image in which the secondary scattering bright lines form a closed region and do not intersect.
3. The method according to claim 2, wherein in said substep C1a, an constant false alarm CFAR detection is used to determine the predetermined threshold.
4. The method according to claim 2, wherein in said substep C1b, the step of selecting a region of interest in the image containing a certain number of first marker points comprises:
scanning pixels in the image by using a pixel window with a predefined size to obtain J first mark point connected regions, wherein the first mark point connected regions refer to the existence of at least one first mark point in adjacent scanning windows of each first mark point in the regions;
k first marker communicated areas with the number of pixels larger than N are selected from the J first marker communicated areas, wherein N is an integer value in the range of 10-20, and K is smaller than J;
using a polygon with the smallest area to surround the K first mark point communicating regions one by one;
determining the enclosed region as the region of interest.
5. A method according to claim 4, wherein the predefined size of the pixel window is P x Q, P being selected from integer values in the range 2-4, Q being selected from integer values in the range 2-4.
6. The method of claim 4, wherein:
in the sub-step C1d, the weights of the second marker points in the at least one region of interest in the image of each height layer are summed according to the following formula:
wherein: smRepresenting the M-th first mark point connected region in the region of interest, wherein M represents the number of the first mark point connected regions of the nth layer image, and T (x)i,yj) Denotes SmIn the region of (x)i,yj) The weight of the second mark point at the position;
in the sub-step C1C, the second marker point is assigned according to the following rule:
wherein, the a1＝2，a2＝1。
7. The method according to claim 2, wherein in said substep C1b a marker extraction method is used to select a region of interest containing a certain number of first marker points.
8. Method according to any one of claims 1 to 7, wherein in step A, the multi-angle observation geometry of the circular track SAR is used for roughly estimating the bottom height H of the target building by adopting a stereo measurement method0。
9. The method of any one of claims 1 to 7, wherein in step B, the imaging range is given by the H0The center height is 4 to 8 times of the stereo measurement precision, wherein the stereo measurement precision is between 1m and 2m in an X wave band; and in the P wave band, the stereo measurement precision is between 3m and 5 m.
10. The method according to claim 9, wherein in the step B, the interval Δ h between two adjacent height layers satisfiesWherein H represents the height between the radar detector and the ground, X represents the horizontal distance between the projection point of the radar detector on the ground and the target building, and C represents the speed of lightAnd B denotes a transmission bandwidth of the radar detector.
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