JPH07199804A - Topographical map generating device employing three-dimensional information obtained by interference type synthetic aperture radar - Google Patents

Abstract

PURPOSE:To generate a highly precise topographical map by compensating for the distortion of a three-dimensional topographical information expressed by the height data taken by an interference type synthetic aperture radar employing a specific method, transforming the coordinate system and compensating shadow. CONSTITUTION:An interference type synthetic aperture radar(SAR) computes the phase differences of SAR image data and converts the SAR image to height data 23 based on the attitude sensor data of a flying object. A foreshortening compensation section 18 of the topographical map generating device compensates for the front tilting phenomenon from the data 23. A pixel size compensation section 19 performs sampling of the output, i.e., three- dimensional data 24, based on a platform velocity information 29 so that the pixel sizes of range/azimuth become the same. Then, a geometric deformation compensation section 20 compensates for the geometric deformation of the output of the section 19 based on a Doppler center frequency 30. A coordinate conversion section 21 converts the output of the section 20 into the topographical map coordinates based on a GPS information 31. The output of the section 21, which is the shadow in the three dimensional information, is replaced by the data which are observed from a different direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention corrects distortion of three-dimensional information obtained by an interferometric synthetic aperture radar device (interferometric SAR) mounted on a flying object such as an aircraft and artificial hygiene to obtain high accuracy. The present invention relates to a topographic map creating device for creating a topographic map.

[0002]

2. Description of the Related Art Conventionally, topographic maps (1 / 25,000-1 / 1 /
In order to create a contour map equivalent to 10,000), aerial survey and stereo vision using an optical camera were performed. However, in these methods, there is a problem that a lot of time is required in principle until the altitude information is extracted, the accuracy is not sufficient, and cloud hour / night observation cannot be performed. In order to solve this problem, a topographic map preparation method using a synthetic aperture radar is disclosed in Japanese Patent Laid-Open No. 63-262578. According to the interference SAR, when needed,
Information can be obtained in real time. This is an interference SA
This is because the elevation is obtained by the calculation process of R, whereas the conventional survey is to obtain the elevation after creating the contour map.
Synthetic aperture radars are disclosed in Japanese Patent Laid-Open Nos. 62-3676 and 62-8081.

[0003]

However, the interference type SAR
The three-dimensional information on the terrain obtained in step 1 includes distortions due to various factors (the speed, attitude of the flying object, for shortening distortion, shadow, etc.). In particular, if the interferometric SAR is mounted on a small aircraft that does not have an inertial navigation system, 3
Dimensional information contains a large amount of distortion, and it was not possible to create a highly accurate topographic map with this three-dimensional information as it is.

FIG. 5 is a conceptual diagram showing the main distortion in the three-dimensional information obtained by the interference SAR. Figure 5 (a)
Represents the pixel size distortion due to the fluctuation of the flying body velocity. (B) represents the for shortening distortion (shift of the peaks) due to the for shortening. Reference numeral 105 indicates an actual side view of the mountain, and reference numeral 106
Is an image of the mountain obtained when the mountain is processed by the interferometric SAR, and is subjected to for shortening distortion. (C) represents the geometric deformation distortion caused by the deviation of the radio wave irradiation direction from the axis perpendicular to the traveling direction. (D) is
Since the image pixel 113 obtained by the interference SAR is obtained by projecting on the coordinate system with the flight object traveling direction as a reference,
This indicates that the topographic map coordinate system (latitude, longitude) 112 is deviated by Δθ. (E) indicates that the shadow 115 causes a drop in the topographic map data.
The pitch, roll, and yaw motions of the flying object are corrected by the interference processing unit of the interference SAR, as shown in FIG.
It does not affect (e). FIG. 5 (a)-
As long as the distortion of the three-dimensional information shown in the conceptual diagram in (e) is not corrected and corrected, it is possible to create a topographical map of a wide area using the three-dimensional information of the output of the interference SAR.

[0005]

Means for Solving the Problems The means provided by the present invention for solving the above-mentioned problems relate to the terrain by radiating radio waves from a flying object toward the ground and receiving reflected waves from the ground. In a topographic map creating apparatus using three-dimensional information obtained from an interferometric synthetic aperture radar apparatus for extracting three-dimensional information, the elevation information generated by the interferometric synthetic aperture radar is received as the three-dimensional information, and the three-dimensional information is obtained. Of the four-shortening distortion, a pixel size correction unit that corrects the pixel size of the three-dimensional information of the output of the four-shortening correction unit based on the velocity information of the flying object, and the dot of the flying object. A geometric deformation correction unit that corrects the geometric deformation of the three-dimensional information output from the pixel size correction unit based on the placenta frequency information; A coordinate conversion unit that converts the coordinate system of the three-dimensional information output from the geometric deformation correction unit from the SAR coordinate system to the topographic map coordinate system based on the GPS information indicating the position of the coordinate transformation unit, and the three-dimensional information output from the coordinate transformation unit. And a topographic map synthesizing unit that replaces the shadows included in the scene with the data observed from another direction, and outputs three-dimensional information of the output of this topographic map synthesizing unit as topographic map information. It is a creation device.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a topographic map producing apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a connection relationship between the embodiment and the interference type SAR, and FIG. 2 is a block diagram showing a configuration of a topographic map creating apparatus of the embodiment. Although this embodiment is mounted on a flying object such as an aircraft, only the interference SAR is mounted on the flying object, and the embodiment is installed on the ground, and the three-dimensional information acquired by the interference SAR is applied offline. It can be operated in the same manner when supplied to.

In FIG. 1, reference numeral 17 represents an interferometric synthetic aperture radar device. The interference processing unit 7 includes the image processing unit 6
After output data 12 and 13 are input and the phase difference between the SAR image data corresponding to the respective antennas 1 and 2 is calculated, the attitude sensor data 1 of the flying body sent from the flying body
The SAR image is corrected with high accuracy based on 6 (pitch, roll, yaw data), and the SAR image is further converted into altitude data, and then the altitude data (elevation information) 23
Is supplied to the topographic map generator 15 of the embodiment as three-dimensional data regarding the topography.

The topographic map generator 15 has the configuration shown in FIG. 2 and performs the following correction on the three-dimensional information based on the correction data 29 to 32.

The foreshortening correction unit 18 is shown in FIG.
The forward movement (four shortening) phenomenon as shown in (b) is corrected from the altitude data 23. The correction is performed by the equation (1). The definition of each parameter is as shown in FIG. P1 is the top of the mountain 102, and the broken line 107 is the flying object 10 relating to the point P1.
The axis trace of equidistant L from 1 and P2 are the intersections of the axis trace 107 of equal distance and the zero elevation line 100. The correction amount is (y ₂ −
y ₁ ). y ₁ is a pixel position before correction, and y ₂ is a correct pixel position. In this process, ground range conversion is also performed at the same time.

Y ₂ = L · sin θ ₂ , θ ₂ = cos ⁻¹ {(H−h) / L}. ． ． (1) Next, the pixel size correction unit 29 samples the three-dimensional data 24 output from the four shortening correction unit 18 based on the flying body velocity information 29 so that the pixel size of the range / azimuth becomes the same. By this sampling, the pixel of FIG. 5A where P ₁ <P ₄ <P ₇ <P ₁₀ becomes P ₁ = P ₄ = P ₇ = P ₁₀ . This sampling is performed by interpolating between pixel data (P _i , P _{i + 1} ) and re-sampling the data at regular intervals ΔP (= azimuth pixel size).

Next, the geometrical deformation correction unit 20 uses the Doppler center frequency 30 to determine the drift angle of the flying object (the axis of the flying object and the traveling direction are flat with respect to the three-dimensional data 25 output from the pixel size correcting unit 19). The distortion caused by the deviation of the irradiation direction of the antenna beam due to
In other words, the antenna beam is fixed to the flying object,
Although the direction of the thick line 111 in FIG. 5C is viewed, the image is converted into a broken line 110 on the image. Therefore, the amount of movement Δ
It is necessary to find L.

Sin φ = (Fd / Fc) · {C / (2Vcosθ)} φ: drift angle (heading angle) θ: off-nadir angle V: flying object velocity Fd: Doppler center frequency Fc: transmission frequency Fd (from SAR data) When 30) is calculated, φ is calculated by the above equation. If φ is known, the thick line 111 is uniquely determined, and ΔL is obtained.

GPS (Global) transmitted from the satellite 40
The 1 Positioning System) signal is received by the GPS device of the flying object, and the GPS data 31 is given to the coordinate conversion unit 21. The coordinate conversion unit 21 uses the GPS data 21.
Δθ is calculated based on and converted into topographic map coordinates. The output signal 27 at this stage is equivalent to the general-purpose topographic map.

However, three-dimensional information by SAR has shadows (see FIG. 5 (e)), and it is necessary to combine it with data observed from another direction. This is the topographic map synthesis unit 22
Is a function of. As shown in FIG. (4), the common figure 10
It is necessary to generate a plurality of three-dimensional data for 3 and to recognize valid data and invalid data (shadow portion) portions 104 and 105 for each three-dimensional data. In the example of FIG. 4, the information of (a) and the information of (b) are combined to create (c).
To generate the information. This process is performed according to the following procedure.

The shadow portion 10 on the SAR image 103
4, 105 are detected. Set the threshold level,
Ranks above the threshold level are flagged as "1", and ranks (shadows) below are flagged as "0". The shadow detection flag information 32 is supplied from the interference SAR 17.

Elevation data of pixels having a "1" flag is valid, and elevation data of pixels having a "0" flag is invalid.

[0017]

As described above, according to the present invention, it is possible to create a topographic map in which the distortion of the three-dimensional information about the topography represented by the elevation data acquired by the interferometric synthetic aperture radar is corrected with high accuracy. . Therefore, if the device of the present invention is adopted, a contour map equivalent to 1 / 25,000 to 1 / 10,000 can be obtained, and compared to aerial survey using a conventional optical camera, a fixed price can be obtained in a short time. Can provide general-purpose topographic maps.

[Brief description of drawings]

FIG. 1 is a block diagram showing a connection relationship between an embodiment of a topographic map creating apparatus according to the present invention and an interference SAR.

FIG. 2 is a block diagram showing a configuration of a topographic map creating apparatus of the embodiment.

FIG. 3 is a diagram showing a concept of for shortening correction in the embodiment of FIG.

FIG. 4 is a diagram showing a concept of shadow correction in the embodiment of FIG.

FIG. 5 is a diagram showing a concept of main distortion included in three-dimensional information about the terrain acquired by the interference SAR.

[Explanation of symbols]

 1, 2 antenna section 3 off-nadir angle setting section 4, 5 transmitting / receiving section 6 image processing section 7 interference processing section 8, 9 transmission / reception signal 10, 11 video signal 12, 13 SAR image data signal 15 topographic map creation device 17 interference type SAR 18 For shortening correction unit 19 Pixel size correction unit 20 Geometric deformation correction unit 21 Coordinate conversion unit 22 Topographic map synthesis unit 29 Flying body velocity information 30 Doppler center frequency 31 GPS signal 32 Shadow detection flag information

Claims (2)

[Claims] 1. Use of three-dimensional information obtained from an interferometric synthetic aperture radar device that emits radio waves from a flying object toward the ground and receives reflected waves from the ground to extract three-dimensional information about the terrain. In the topographic map creating apparatus, a foreshortening correction unit that receives elevation information generated by the interferometric synthetic aperture radar as the three-dimensional information and corrects foreshortening distortion of the three-dimensional information,
A pixel size correction unit that corrects the pixel size of the three-dimensional information of the output of the foreshortening correction unit based on the velocity information of the flying object, and an output of the pixel size correction unit based on Doppler center frequency information of the flying object Of 3
A geometrical deformation correction unit that corrects geometrical deformation of the dimensional information, and a coordinate system of three-dimensional information output from the geometrical deformation correction unit based on GPS information indicating the position of the flying object is changed from the SAR coordinate system to the topographic map coordinate system. It has a coordinate transformation unit for transformation and a topographic map synthesis unit that replaces shadows contained in the scene in the three-dimensional information output from this coordinate transformation unit with data observed from another direction. A topographic map creation device characterized by outputting three-dimensional information as topographic map information. 2. The geometric deformation correction section utilizes the drift angle of the flying object given from the flying object so that the antenna beam irradiation direction of the interference type synthetic aperture radar is the traveling direction of the interference type synthetic aperture radar. The topographic map creation apparatus according to claim 1, wherein geometric deformation of the three-dimensional information due to deviation is corrected.