A method for measuring the obscuration angle of a panoramic image

Abstract

The present invention discloses a method for measuring the shielding angle of a panoramic image, which comprises the following steps: step 1, hanging a panoramic camera on a mobile terminal; step 2, selecting a data collection point where the shielding angle needs to be measured, and collecting a panoramic image at the data collection point through the panoramic camera; step 3, collecting relevant data such as a gyroscope, GPS, a direction sensor, and a gravity sensor; step 4, synchronizing the data obtained in step 3 and calculating relevant environmental parameters; step 5, recording GPS information of the data collection point, correcting the panoramic data through the data collected by the direction sensor, correcting it to a horizontal position, and obtaining a panoramic image of the horizontal position of the current point; step 6, unfolding the panoramic image, and after unfolding, calculating the shielding angle according to the configured parameters to obtain the shielding angle to be measured.

Description

Technical Field

[0001] The present invention relates to the technical field of shielding angle measurement, and in particular to a method for measuring the shielding angle of a panoramic image. Background Art

[0002] Radar shielding angle refers to the lowest angle at which a radar antenna can detect a target while emitting electromagnetic waves in a specific direction. When the minimum elevation angle is greater than the elevation angle of the radar antenna, the radar waves emitted by the antenna are obstructed by terrain or objects in the line of sight, rendering the target invisible to the radar. Radar shielding angle is a key battlefield environmental factor that restricts radar detection capabilities. Measuring and mapping radar shielding angles is a crucial component of radar station combat preparation. Therefore, when selecting a radar station location, the shielding angle around the location is a crucial consideration. Only by accurately measuring the shielding angles in all directions of a radar location and understanding the potential blind spots of the radar can we scientifically select radar locations and lay a solid foundation for conducting air reconnaissance missions.

[0003] However, the existing shielding angle measurement requires that staff first be sent to a designated location to set up the measuring equipment and then start the equipment before measurement can be carried out, which is time-consuming and labor-intensive. Summary of the Invention

[0004] In response to the above-mentioned problems, the present invention proposes a panoramic image obscuration angle measurement method, which uses VR panoramic images to calculate the obscuration angle. In the field environment, since the mobile terminal is connected to an external panoramic camera, it is easy to carry and easy to operate. It is very suitable for collecting environmental data such as obscuration angle in the field environment and is very practical.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for measuring a panoramic image obscuration angle, comprising the following steps:

[0007] Step 1: Mount the panoramic camera on the mobile terminal;

[0008] Step 2: Select a data collection point where the shielding angle needs to be measured, and collect a panoramic image at the data collection point using a panoramic camera;

[0009] Step 3: Collect relevant data such as gyroscope, GPS, direction sensor, gravity sensor, etc.

[0010] Step 4: Synchronize the data and calculate relevant parameters;

[0011] Step 5: Record the GPS data collection point, and use the data collected by the direction sensor to correct the panoramic data to the horizontal position to obtain a panoramic view of the horizontal position of the current point;

[0012] Step 6: Expand the panorama, and then calculate the shielding angle according to the configured parameters to obtain the shielding angle to be measured.

[0013] The beneficial effects of the present invention are:

[0014] First, in a field environment, the present invention uses a panoramic camera connected to an external mobile terminal to shoot a panoramic picture. The obtained panoramic picture is image data with a visible range of 360°. Existing measuring equipment generally has distance limitations, and the ordinary pictures it shoots are only a partial angle range in one direction. Therefore, the panoramic picture shot by the panoramic camera is more suitable for collecting environmental data of the shielding angle in the field environment for subsequent shielding angle calculation.

[0015] Second, the present invention uses a portable mobile terminal and a panoramic camera to eliminate the need for staff to deploy measurement equipment at designated locations. Instead, they can collect data while moving with a portable tablet, saving measurement time, making it easier for users to screen the required measurement locations, and improving measurement efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a diagram of the Android orientation sensor coordinate system;

[0017] Figure 2 It is a projection diagram that expands the spherical panoramic image into a flat image;

[0018] Figure 3 This is a schematic diagram of a panoramic image unfolded into a 12-sided plane image. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0020] The present invention uses a panoramic image to calculate the obstruction angle. In an environment with good visibility in the wild, a panoramic camera is mounted on the Type-C port of a mobile terminal, and panoramic images are collected at the data collection point. During the collection, relevant data information of sensors such as the mobile terminal's gyroscope, GPS, direction sensor, and gravity sensor are synchronously collected and inserted into a database (sqllite) established by the machine. According to the data collected from the gyroscope, magnetic field sensor, etc. of the current device, the deflection angle and movement of the current camera are obtained, and the GPS information of the data collection point is recorded. The panoramic data is corrected to a horizontal position using the data collected by the direction sensor. A panoramic image of the horizontal position of the current point is obtained, and the panoramic image is expanded. After expansion, the obstruction angle is calculated according to preset parameters (related to the device and user settings, parameters for camera shooting and conversion of images, etc.). After obtaining the data, the obstruction angle is displayed and processed accordingly.

[0021] The mobile terminal used in the present invention is a Huawei tablet computer, so an Android device will be taken as an example for introduction.

[0022] 1. Magnetic sensor

[0023] On the Android platform, the magnetic sensor, referred to as M-sensor, returns ambient magnetic field data along the x, y, and z axes. The value is expressed in microteslas (µT). Gauss is also supported, with 1 Tesla equal to 10,000 Gauss.

[0024] 2. Gyroscope

[0025] A gyroscope has a spinning top inside it. Its axis is always parallel to the initial direction due to the gyroscopic effect. This allows the actual direction to be calculated based on the deviation from the initial direction. The gyroscope in an Android device is a very sophisticated chip that contains an ultra-small gyroscope.

[0026] The gyroscope's detection of device rotation angles is instantaneous and highly accurate, meeting the needs of applications requiring high resolution and fast response. Therefore, VR panoramas primarily rely on the changes in this instrument's values ​​for display.

[0027] SensorManager is a class in Android. It has a function getRotationMatrix, which can calculate the rotation matrix through the current magnetic sensor data and gyroscope data, and then obtain the direction of the device (heading angle, pitch angle, roll angle) through getOrientation, such as Figure 1 shown.

[0028] 3. VR Panorama Processing

[0029] 1. Data sampling

[0030] Mobile terminal devices generally capture panoramic images while they are moving (in motion). During the image capture process, information such as the mobile terminal's gyroscope, direction sensor, and gravity sensor is synchronously collected into the database. The gyroscope can be used to know the movement of the device per unit time. Video images with unstable states such as excessively high movement frequency (vibration, high shaking frequency) and excessive movement amplitude are avoided as much as possible. Instead, data sampling is performed on stable and smoothly moving panoramic images.

[0031] 2. Data preprocessing

[0032] Based on the collection time of sensor data such as the gyroscope (for example, the collection frequency is set to 10 times per second), the panoramic image data is sliced ​​(sliced ​​into panoramic images). For each collection point (GPS) image, nearly 10 panoramic images are analyzed and processed. During the collection process, most image data is not shot in a horizontal direction. Through the direction sensor data, the panoramic image data is processed into a horizontal position and then saved as a standard panoramic image. Each panoramic image is expanded and converted into a normal image. The expansion algorithm is as follows:

[0033] When converting from a flat surface to a sphere, a straight line is drawn from the center of the circle through each pixel of the flat image and projected onto the sphere, transferring the flat pixels to the sphere. The reverse process is used for plane mapping. While the resulting image is spherical, it only appears to be spherical visually; the image structure remains two-dimensional pixels.

[0034] Attachment Figure 2 This is a schematic diagram of mapping a sphere to a plane. When mapping a sphere to a plane, a new plane image needs to be created. Loop through the horizontal and vertical left points of the plane image (the grid points in the array on the left plane), traverse each point, and connect each point with the center o of the circle. On the projected sphere, the arc length between the point on the sphere and the left and right boundaries of the spherical image is the horizontal coordinate of the spherical image we require. The arc length is calculated by multiplying the central angle of the circle by the radius of the sphere. Combined with the attached Figure 2 To calculate the central angle: Figure 2Point A on the circle is an arbitrary point on the plane. The central angle is the angle between Ao and the red line EO, which is the angle between Do and the red line EO minus the angle between Do and Ao. The side DE corresponding to the angle between Do and the red line EO is half the length of the plane image, assuming it is length / 2. The length of Do can be calculated using the Pythagorean theorem using the right triangle DCo: sqrt(y*y+length / 2*length / 2). Assuming E is the intersection of the red line and the horizontal line containing A, ED is length / 2. Therefore, DoE = arctan(ED / Do). DoA = arctan((length / 2-x) / Do). Therefore, AoE is DoE - DoA = arctan(ED / Do) - arctan((length / 2-x) / Do). Simply multiplying this angle by the radius R gives you the horizontal coordinate. When the point is in the right half of the plane, convert length / 2-x to x-length / 2.

[0035] Solving for the ordinate is similar to solving for the abscissa. Simply find the angle A⁻B. Using the Pythagorean theorem for a right triangle between BC and oC, find Bo. Then, A⁻B is simply arctan(AB / Bo). The length of this arc on the sphere is arctan(AB / Bo)*R. This gives us the arc length, but since we need the ordinate of the spherical image, we need to subtract the arc length from half the height of the spherical image. This gives us the coordinates for each point. Once we have the abscissa and ordinate coordinates, we can display the image.

[0036] Because it is a 360-degree panorama, after obtaining a portion of the plan at a set angle (which must be divisible by 360), continue rotating this angle and continue obtaining the plan according to the previous steps until the rotation is complete. Then, all the obtained plan images are spliced ​​together to form a complete panoramic plan, as shown in the attached figure. Figure 3 As shown, it is an example of a 12-sided polygon after expansion.

[0037] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for measuring the obscuration angle of a panoramic image, characterized in that: The following steps are involved: Step 1: Mount the panoramic camera on the mobile terminal; Step 2: Select a data collection point where the shielding angle needs to be measured, and collect a panoramic image at the data collection point using a panoramic camera; Step 3: Collect relevant data from the gyroscope, GPS, directional sensor, and gravity sensor; Step 4: Synchronize the data obtained in step 3 and calculate the relevant environmental parameters; Step 5: Record the GPS information of the data collection point, and use the data collected by the direction sensor to correct the panoramic data to the horizontal position to obtain a panoramic view of the horizontal position of the current point; Step 6: Expand the panorama, calculate the shielding angle according to the configured parameters, and obtain the shielding angle to be measured; Wherein, step 6 includes the following steps: Step 61: Expand the spherical panoramic image into a flat ordinary image starting from the true north direction; Step 62: The expanded plane ordinary image is subjected to contour edge extraction processing by grayscale and binarization to obtain the sky-air intersection segmentation line; Step 63: Based on the position of the sky-air intersection dividing line in the image, calculate the obstruction angle from top to bottom, divide the interval into 360 degrees from left to right, and smooth the mean sampling to finally obtain the obstruction angle to be measured; Step 61 includes the following steps: Step 611: input a spherical panoramic image; Step 612: Create a new plane image, loop through the horizontal and vertical left points of the created plane image, traverse each point, and draw a line connecting each point with the center of the circle o, and project it onto the spherical surface of the panoramic image. The arc length between the point on the spherical surface and the left and right boundaries of the spherical panoramic image is the horizontal coordinate of the spherical image; Step 613: Apply geometric operations to obtain the arc length, and thus the horizontal coordinate of the spherical image; Step 614: Loop through the horizontal and vertical right points of the created plane image, traverse each point, and draw a line connecting each point with the center of the circle o, and project it onto the spherical surface of the panoramic image. The arc length between the point on the spherical surface and the left and right boundaries of the spherical panoramic image is the vertical coordinate of the spherical image; Step 615: Apply geometric operations to obtain the arc length mentioned in step 614, so as to know the vertical coordinate of the spherical image; Step 616: Display the plane image according to the obtained horizontal and vertical coordinates; Step 617: Obtain a plane image according to a preset rotation angle. At this time, the spherical panoramic image rotates at the same time. Continue to rotate the angle and obtain a second plane image according to steps 612-616 until the rotation is completed 360 degrees. Finally, the n plane images are obtained and stitched together to obtain the final plane expansion image of the panoramic image.

Images