Method for estimating the area of an irregularly shaped fire ground using an optoelectronic pod

Abstract

The method for estimating the area of an irregular-shaped fire scene using an optoelectronic pod in the present invention belongs to the technical fields of navigation control algorithms and infrared image processing, and includes: S101: Preprocessing and background suppression are performed on the infrared thermal image, and the fire scene area in the image is identified according to the gray value of the image and the set temperature threshold; S102: Determine the slant range information of the fire scene area aligned with the optical axis of the pod; S103: Place the infrared thermal image in a rectangular coordinate system with the alignment point of the pod optical axis as the origin, and the fire scene area forms an irregular area in the rectangular coordinate system; S104: Calculate the area projected onto the actual ground for each pixel in the fire scene area according to the optical axis attitude, geographical location information, and slant range information, and add up the projected areas of each pixel to obtain the fire scene area on the actual ground. It can greatly improve the efficiency of forest fire prevention emergency rescue and the accuracy and real-time nature of fire situation reports, thereby achieving rapid analysis of forest fire situations and providing strong information support for forest fire fighting and emergency command.

Description

Technical Field

[0001] The present invention belongs to the technical fields of navigation control algorithms and infrared image processing, and particularly relates to a method for estimating the area of an irregularly shaped fire field using an optoelectronic pod. Background Art

[0002] Forest fires are one of the most serious disasters that damage and affect forests, causing serious casualties and property losses every year. The forest fire prevention monitoring and early warning system based on aircraft and optoelectronic pod technology can be used as an important tool for forest fire prevention emergency rescue and forest fire fighting. Using an optoelectronic pod to estimate the area of a fire field is of great significance, which can greatly improve the efficiency of forest fire prevention emergency rescue and the accuracy of fire situation reports.

[0003] Currently, at home and abroad, many optoelectronic pods can obtain the geographical location information of the ignition point through the attitude and position determination system in the pod. However, there are few optoelectronic pods that can estimate the area of the fire field. Among the individual ones that can estimate the area of the fire field, there are also problems such as rough estimation and poor estimation accuracy, and they can only estimate the area of regularly shaped fire fields. Summary of the Invention

[0004] In view of this, the present invention provides a method for estimating the area of an irregularly shaped fire field using an optoelectronic pod, which at least partially solves the technical problem of low accuracy in calculating the area of the fire field in the existing technical methods.

[0005] Provided is a method for estimating the area of an irregularly shaped fire field using an optoelectronic pod. The optoelectronic pod is installed on an aircraft platform and can obtain an infrared thermal image of the fire area. The optoelectronic pod is equipped with an attitude and position determination system for obtaining the geographical location information of the pod and the attitude information of the pod optical axis. The method includes:

[0006] S101: Preprocess the infrared thermal image and suppress the background, and identify the fire field area in the image according to the gray value of the image and a set temperature threshold. In the conventional method of the prior art for preprocessing, the purpose is to enhance the image characteristics. For the set temperature threshold, for example, 120°, the gray value is converted into a temperature value;

[0007] S102: Determine the slant range information of the fire field area aligned with the pod optical axis;

[0008] S103: Place the infrared thermal image in a rectangular coordinate system with the alignment point of the pod optical axis as the origin, and the fire field area forms an irregular area in the rectangular coordinate system;

[0009] S104: Calculate the area projected onto the actual ground for each pixel in the fire field area according to the optical axis attitude, geographical location information, and slant range information, and add up the projected areas of each pixel to obtain the fire field area on the actual ground.

[0010] Technical beneficial effects of the present invention:

[0011] It is possible to estimate the area of a fire field of any shape, and this method can be used whether there is a laser rangefinder in the optoelectronic pod or not. It does not require the image center to be aligned with the fire field. As long as the fire field enters the field of view, the area of the fire field can be estimated accurately and quickly, and real-time estimation can be achieved. This can greatly improve the efficiency of forest fire prevention emergency rescue, the accuracy and real-time nature of fire reports, so as to realize the rapid analysis of forest fires and provide strong information support for forest fire fighting and emergency command. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0013] Figure 1 It is a schematic diagram of the fire field area and infrared image coordinates of the present invention;

[0014] Figure 2 It is a schematic diagram of the spatial coordinates of the optoelectronic pod and the observation area of the present invention;

[0015] Figure 3 It is a cross-sectional view of the spatial coordinates of the optoelectronic pod and the observation area of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] The embodiments of the present disclosure will be described in detail below with reference to the drawings.

[0017] The following specific examples illustrate the implementation manners of the present disclosure. Those skilled in the art can easily understand other advantages and effects of the present disclosure from the content disclosed in this specification. Obviously, the described embodiments are only some embodiments of the present disclosure, rather than all embodiments. The present disclosure can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts belong to the scope of protection of the present disclosure.

[0018] It should be noted that the following description relates to various aspects of embodiments within the scope of the appended claims. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is illustrative only. Based on this disclosure, those skilled in the art should understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of the aspects set forth herein can be used to implement a device and / or practice a method. Additionally, this device can be implemented and this method can be practiced using other structures and / or functionality in addition to one or more of the aspects set forth herein.

[0019] The method for estimating the area of an irregularly shaped fire scene using an optoelectronic pod according to the present invention, wherein the optoelectronic pod is installed on an aircraft platform and can obtain an infrared thermal image of the fire area. The optoelectronic pod is equipped with a pose and positioning system for obtaining the geographical location information of the pod and the attitude information of the optical axis of the pod. The method includes:

[0020] S101: Preprocess the infrared thermal image and suppress the background, and identify the fire scene area in the image according to the gray value of the image and a set temperature threshold. Specifically,

[0021] The preprocessing and background suppression are performed using conventional methods to enhance the image characteristics. For the set temperature threshold, for example, 120°, the gray value is converted into a temperature value;

[0022] An infrared sensor is installed inside the optoelectronic pod to collect the estimated temperature values of each pixel point in the infrared image to form an infrared thermal image. There is a pose and positioning system (POS) in the POS, which has a GPS and an inertial attitude measurement unit, and can obtain the geographical location information of the pod and the attitude information of the optical axis of the pod in real time;

[0023] S102: Determine the slant range information of the fire scene area aligned with the optical axis of the pod. Specifically, the slant range L between the pod and the ground point aligned with the center of the optical axis of the pod. For an optoelectronic pod equipped with a laser rangefinder, L can be directly obtained through laser ranging. For a pod without a laser rangefinder, a passive positioning method is adopted. The pod can obtain the GPS coordinates of the pod through the pose and positioning system (POS), and the attitude angle of the optical axis of the pod obtained by the pose and positioning system. By obtaining the observation information of two groups of aligned target points, the geographical location information of the target aligned with the center of the optical axis is calculated through coordinate transformation and triangular transformation, so as to obtain the slant range between two points. When the altitude of the target point is known, L can also be directly calculated through the altitude difference between the pod and the target and the pitch attitude angle of the optical axis of the pod.

[0024] S103: Place the infrared thermal image in a rectangular coordinate system with the alignment point of the pod optical axis as the origin. The fire area forms an irregular area in the rectangular coordinate system. The pixel resolution of the infrared image is A×B, and the field of view angle is α×β. The irregular area is projected in the coordinate system. After projection, the irregular area consists of multiple pixel points forming multiple horizontal line segments. The ordinate values of all line segments are y1, y2...y n , and the number of pixels are l1, l2...l n ;

[0025] To estimate the area of an irregularly shaped fire using an optoelectronic pod, as Figure 1 shown, first, the pod needs to be pointed at the fire area in the air to obtain an infrared image containing the fire area. The actual ground fire area corresponding to each pixel in the fire area of the image can be estimated, such as the shaded area in the figure, and then the area of the forest fire area can be estimated. Since the roll angle of the aircraft is small during flight, at this time, as Figure 2 shown, the projection range of the infrared image observed by the pod on the ground can be approximated as a trapezoid, and its cross-section is as Figure 3 shown. The area of this trapezoid can be estimated by adding the areas of multiple rectangles with a projection length of 1 pixel width.

[0026] S104: Calculate the area projected onto the actual ground for each pixel in the fire area based on the optical axis attitude, geographical location information, and slant range information, and add up the projected areas of each pixel to obtain the fire area on the actual ground. Specifically,

[0027] Obtain the pitch angle θ corresponding to the center of the pod optical axis in real time through the pose and positioning system;

[0028] y i The projection length of a single pixel in the pitch direction of the corresponding infrared image on the ground is M i , satisfying:

[0029] where L is the slant range;

[0030] Calculate the projection length L of the azimuth direction corresponding to the y i coordinate on the ground through trigonometric functions yi , satisfying:

[0031]

[0032] y i The projection length of the azimuth direction l i corresponding to the y i coordinate on the ground for l

[0033]

[0034] The area S of the fire scene can be calculated by multiplying the length Mi of the projection of a single pixel in all pitch directions and the length Ni of the projection of the pixels in the fire scene area in the azimuth direction on the ground. For example, the area S of the actual fire scene satisfies:

[0035]

[0036] As a specific implementation manner provided in this case, the pixel points with the ordinate y directly above or below the center line of the field of view are projected onto the ground, and the pitch angle corresponding to the projection line is i

[0037] The control method of the present invention can estimate the area of a fire scene with any shape, and this method can be used whether there is a laser rangefinder in the optoelectronic pod or not. It does not require the image center to be aligned with the fire scene. As long as the fire scene enters the field of view, the area of the fire scene can be estimated accurately and quickly, and real-time estimation can be achieved. It can greatly improve the efficiency of forest fire prevention and emergency rescue, as well as the accuracy and real-time nature of the fire situation report, so as to quickly analyze the forest fire situation and provide strong information support for forest fire fighting and emergency command.

[0038] The above is only a specific implementation manner of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present disclosure should be covered by the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.​

Claims

1. A method for estimating the area of an irregularly shaped fire field using an optoelectronic pod. The optoelectronic pod is installed on an aircraft platform and can obtain an infrared thermal image of the fire area. The optoelectronic pod is equipped with a pose and positioning system for obtaining the geographical position information of the pod and the attitude information of the optical axis of the pod. It is characterized in that, The method includes: S101: Preprocess the infrared thermal image and suppress the background, and identify the fire area in the image according to the gray value of the image and the set temperature threshold; S102: Determine the slant range information of the fire area aligned with the pod optical axis; S103: Place the infrared thermal image in a rectangular coordinate system with the alignment point of the pod optical axis as the origin, and the fire area forms an irregular area in the rectangular coordinate system; S104: Calculate the area projected onto the actual ground for each pixel in the fire area according to the optical axis attitude, geographical location information, and slant range information, and sum the projected areas of each pixel to obtain the fire area on the actual ground, where The pixel resolution of the infrared image is A×B, and the field of view angle is α×β; The irregular area is projected in the coordinate system. The irregular area after projection is composed of multiple horizontal line segments composed of multiple pixel points. The vertical coordinate values of all line segments are y1, y2...y n , and the number of pixels are l1,l2...l n ; Obtain the attitude pitch angle θ corresponding to the center of the pod optical axis in real time through the pose and positioning system; y i The length of the projection of a single pixel in the pitch direction of the corresponding infrared image on the ground is M i , satisfying: Wherein, L is the slant range; Calculate y through trigonometric functions i The projection length L of the azimuth direction corresponding to the coordinates on the ground yi , satisfy: y i The azimuth direction l corresponding to the coordinates i The length of the projection of a pixel on the ground is N i , satisfying: The area S of the fire can be calculated by multiplying the length Mi of the projection of a single pixel in all pitch directions by the length Ni of the projection of the pixels in the azimuth direction of the fire area on the ground.

2. The method according to claim 1, wherein The method in S102 includes: For an optoelectronic pod equipped with a laser rangefinder, it can be directly obtained through laser ranging. For a pod without a laser rangefinder, it can be obtained through passive positioning by the pose and positioning system in the pod.

3. The method according to claim 1, wherein The area S of the actual fire satisfies:

4. The method according to claim 3, characterized in that, The pixel point with the ordinate of y directly above or below the center line of the field of view i is projected onto the ground, and the pitch angle corresponding to the projection line is

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