A method for extracting the height of vertical objects in aerial CCD remote sensing images

Abstract

The invention discloses a method for extracting the height of a vertical object on an aerial array CCD remote sensing image. The method applies a strict imaging geometric relationship model of the aerial array CCD remote sensing image, and calculates the vertex image coordinates and the bottom image coordinates of the vertical object by using coordinate transformation coefficients and projection scale coefficients calculated according to the posture of an aircraft to obtain the height of the vertical object. It is unnecessary to extract other features of the vertical object and it is also unnecessary to use two image data. Therefore, the invention can simplify the process of extracting the height information of various vertical objects on the aerial array CCD remote sensing image.

Description

Technical Field

[0001] The invention belongs to the technical field of remote sensing image processing, and in particular relates to a method for extracting the height of a vertical object on an aerial array CCD remote sensing image. Background Art

[0002] With the continuous progress and development of aerial remote sensing technology, the advantages of aerial array (Charge Coupled Device, CCD) remote sensing images, such as large ground coverage, high spatial resolution, and good geometric rigidity, have made them widely used in various industries. In aerial array CCD remote sensing applications, certain thematic information is often extracted and analyzed, and vertical features are a special type of thematic features, such as various types of industrial chimneys, various tower structures, transmission poles, high-rise buildings, etc. These features stand vertically on the ground, and their height is much greater than their length or width. When using aerial CCD remote sensing images to analyze such vertical features, it is often necessary to extract their height information.

[0003] At present, the methods for extracting the height of ground objects from aerial remote sensing images mainly include the extraction method based on single CCD remote sensing images and the extraction method based on aerial stereo CCD images.

[0004] The method of extracting the height of the object based on a single CCD remote sensing image mainly utilizes the shadow feature information of the object on the aerial CCD image. The root cause of the shadow of the upright object on the image is the different azimuths and altitudes of the sun and the aircraft. When the azimuth and altitude of the sun and the aircraft are the same or the solar altitude angle is greater than or equal to the aircraft altitude angle, there is no shadow on the image; when the solar altitude angle is less than the aircraft altitude angle, there is a shadow on the image, which is manifested as a low brightness value on the image, which is conducive to identification. According to the different positions of the aircraft when the aerial CCD image is imaged, the shadow information on the image has a clear geometric relationship with the altitude angle of the sun and the aircraft. Therefore, the height of the object can be solved by using the clear geometric relationship between the shadow of the upright object and its height, the altitude angle and azimuth of the sun, and the altitude angle and azimuth of the aircraft, so as to finally infer the height information of the upright object based on the altitude angle and azimuth of the aircraft and the sun when the CCD remote sensing image is imaged, and the length of the shadow of the upright object on the image.

[0005] The method of extracting the height of vertical objects based on aerial stereo CCD images is to obtain two images of the same object to form a stereo pair. According to the two reverse projection rays of the same-name image points of the vertical object in the two images, the height of the object point can be determined based on the principle of forward intersection. Its essence is to geometrically reverse the photography process to obtain the height of the object point. The prerequisite for extracting the height of vertical objects based on aerial stereo CCD images is that there must be two images (two images obtained at different positions) and there is a certain degree of overlap between the two images, and the overlapping parts constitute a "stereo pair". Therefore, using stereo images to obtain the three-dimensional position of the ground requires the following points: 1. Obtain two images at least at two positions; 2. Extract the same-name points on the two images, which is generally achieved by image matching; 3. Restore the spatial orientation of the two corresponding straight lines, and finally obtain the height value of the object point; At present, aerial stereo measurement technology is relatively mature and has been commercialized. For example, software such as Pix4Dmapper, PhotoScan, PixelGrid, etc. can realize the height extraction of various objects.

[0006] It can be seen that the method of extracting the height of upright objects based on a single CCD remote sensing image must have shadows on the aerial CCD image, and the formation of shadows depends on the sun and the relationship between the sun's altitude angle and the aircraft's altitude angle. Once there is no shadow on the aerial CCD remote sensing image, this method cannot extract the height of the object. In some cases, the actual aerial CCD remote sensing image cannot obtain the shadow of the object on the image due to various reasons. In this case, the height of the upright object cannot be extracted. When there is only one aerial CCD remote sensing image, the method of extracting the height of upright objects based on aerial stereo CCD images cannot be used to extract the height information of the object.

[0007] In summary, the existing method of extracting the height of vertical objects based on a single CCD remote sensing image has the problem of relying on the shadow of the object, while the method of extracting the height of vertical objects based on aerial stereo CCD images has the disadvantage of requiring at least two images for analysis. Summary of the invention

[0008] In view of this, the present invention provides a method for extracting the height of upright objects on an aerial array CCD remote sensing image, which can calculate the height of the upright objects according to the geometric relationship of aerial array CCD imaging.

[0009] The present invention provides a method for extracting the height of vertical objects on an aerial array CCD remote sensing image, comprising the following steps:

[0010] Extract the bottom image coordinates and top image coordinates of the vertical object to be analyzed on the aerial array CCD remote sensing image to obtain the three-dimensional position and posture of the aircraft; calculate the coordinate rotation coefficient according to the posture; calculate the coordinate transformation coefficient according to the coordinate rotation coefficient, the bottom image coordinates of the vertical object to be analyzed and the focal length of the aerial camera; calculate the projection scale coefficient according to the coordinate transformation coefficient; calculate the height value of the vertical object to be analyzed according to the image coordinates of the vertical object to be analyzed, the coordinate rotation coefficient and the projection scale coefficient.

[0011] Furthermore, the method of acquiring the three-dimensional position and attitude of the aircraft is to obtain the three-dimensional position and attitude by reading an aviation array auxiliary data file.

[0012] Furthermore, the coordinate rotation coefficients (a1, a2, a3, b1, b2, b3, c1, c2, c3) are calculated using formula (1):

[0013]

[0014] in, is the pitch angle of the aircraft, ω is the roll angle of the aircraft, and κ is the heading angle of the aircraft;

[0015] According to the calculated coordinate rotation coefficients (a1, a2, a3, b1, b2, b3, c1, c2, c3), the bottom image coordinates (x1, y1) of the vertical feature to be analyzed and the focal length f of the aerial camera, the coordinate transformation coefficients (l1, l2, m1, m2, n1, n2) are calculated using formula (2):

[0016]

[0017] According to the calculated coordinate transformation coefficients (l1, l2, m1, m2, n1, n2), the projection scale coefficients K1 and K2 are calculated using formula (3):

[0018]

[0019] Furthermore, the method of calculating the height value h of the vertical feature to be analyzed according to the image coordinates of the vertical feature to be analyzed, the coordinate rotation coefficient and the projection scale coefficient is to use formula (4) to calculate:

[0020]

[0021] Among them, H0 is the height of the ground.

[0022] Furthermore, the method of extracting the base image coordinates and the vertex image coordinates of the vertical object to be analyzed on the aerial array CCD remote sensing image is to use image analysis software to analyze the aerial array CCD remote sensing image to obtain the base image coordinates and the vertex image coordinates.

[0023] Beneficial effects:

[0024] The present invention applies a strict imaging geometric relationship model of aerial array CCD remote sensing images, and calculates the vertex image coordinates and the bottom image coordinates of the upright objects by means of coordinate transformation coefficients and projection scale coefficients calculated according to the posture of the aircraft to obtain the height of the upright objects. There is no need to extract other features of the upright objects, and there is no need to use two image data. Therefore, the present invention can simplify the process of extracting height information of various upright objects on aerial array CCD remote sensing images. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention provides a flow chart of a method for extracting the height of vertical objects on an aerial array CCD remote sensing image. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0027] The present invention provides a method for extracting the height of a vertical object on an aerial array CCD remote sensing image. The core idea is: using the geometric relationship model of the aerial array rigorous imaging, using the position information of the vertical object to be analyzed and the speed and attitude information of the aircraft extracted from the aerial array CCD remote sensing image, and then calculating the coordinate rotation coefficient according to the attitude of the aircraft, and then calculating the coordinate conversion coefficient according to the coordinate rotation coefficient, the bottom point image coordinates and the camera focal length, calculating the projection scale coefficient according to the coordinate conversion coefficient, and finally calculating the height of the vertical object to be analyzed according to the image coordinates, the coordinate rotation coefficient and the projection scale coefficient.

[0028] The present invention provides a method for extracting the height of vertical objects on an aerial array CCD remote sensing image, the process is as follows: Figure 1 As shown, the specific steps include:

[0029] Step 1: Use image analysis software to extract the bottom image coordinates (x1, y1) and top image coordinates (x2, y2) of the vertical features to be analyzed contained in the aerial array CCD remote sensing image, and read the aerial array auxiliary data file to obtain the flight altitude Z of the aircraft corresponding to the aerial array CCD remote sensing image. s and posture in, represents the pitch angle of the aircraft, ω represents the roll angle of the aircraft, and κ represents the heading angle of the aircraft.

[0030] Step 2: Calculate the coordinate rotation coefficient (a1, a2, a3, b1, b2, b3, c1, c2, c3) according to the aircraft attitude obtained in step 1. The calculation formula is shown in formula (1):

[0031]

[0032] Among them, sin is the trigonometric sine function, and cos is the trigonometric cosine function.

[0033] Step 3: Calculate the coordinate transformation coefficient (l1, l2, m1, m2, n1, n2) according to the coordinate rotation coefficient calculated in step 2, the bottom image coordinates of the vertical object to be analyzed and the focal length of the aerial camera. The calculation formula is shown in formula (2):

[0034]

[0035] Wherein, f is the focal length of the aerial camera, which can be provided by the camera manufacturer.

[0036] Step 4: Calculate the projection scale coefficients K1 and K2 according to the coordinate transformation coefficients calculated in step 3. The calculation formula is shown in formula (3):

[0037]

[0038] Step 5: Calculate the height h of the vertical feature to be analyzed according to the image coordinates, coordinate rotation coefficients and projection scale coefficients of the vertical feature to be analyzed obtained in the above steps. The calculation formula is shown in formula (4):

[0039]

[0040] Among them, H0 is the height of the ground.

[0041] It can be seen that the method for extracting the height of upright objects on aerial array CCD remote sensing images provided by the present invention applies a strict imaging geometric relationship model of aerial array CCD remote sensing images. The geometric relationship is strict, no other features of the objects are extracted, and no two image data are used. The height of the upright objects can be directly calculated without initial value setting and iterative process.

[0042] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for extracting the height of vertical objects on an aerial array CCD remote sensing image, characterized in that: The following steps are involved: Extract the bottom image coordinates and top image coordinates of the vertical object to be analyzed on the aerial array CCD remote sensing image to obtain the three-dimensional position and posture of the aircraft; calculate the coordinate rotation coefficient according to the posture; calculate the coordinate transformation coefficient according to the coordinate rotation coefficient, the bottom image coordinates of the vertical object to be analyzed and the focal length of the aerial camera; calculate the projection scale coefficient according to the coordinate transformation coefficient; calculate the height value of the vertical object to be analyzed according to the image coordinates of the vertical object to be analyzed, the coordinate rotation coefficient and the projection scale coefficient; The coordinate rotation coefficients (a1, a2, a3, b1, b2, b3, c1, c2, c3) are calculated using formula (1): in, is the pitch angle of the aircraft, ω is the roll angle of the aircraft, and κ is the heading angle of the aircraft; According to the calculated coordinate rotation coefficients (a1, a2, a3, b1, b2, b3, c1, c2, c3), the bottom image coordinates (x1, y1) of the vertical feature to be analyzed and the focal length f of the aerial camera, the coordinate transformation coefficients (l1, l2, m1, m2, n1, n2) are calculated using formula (2): According to the calculated coordinate transformation coefficients (l1, l2, m1, m2, n1, n2), the projection scale coefficients K1 and K2 are calculated using formula (3): The method of calculating the height value h of the vertical object to be analyzed according to the image coordinates of the vertical object to be analyzed, the coordinate rotation coefficient and the projection scale coefficient is to use formula (4) to calculate: Among them, H0 is the height of the ground.

2. The extraction method according to claim 1, characterized in that The method of acquiring the three-dimensional position and attitude of the aircraft is: obtaining the three-dimensional position and attitude by reading the aviation array auxiliary data file.

3. The extraction method according to claim 1, characterized in that The method of extracting the base image coordinates and the vertex image coordinates of the vertical object to be analyzed on the aerial array CCD remote sensing image is to use image analysis software to analyze the aerial array CCD remote sensing image to obtain the base image coordinates and the vertex image coordinates.

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