菜鸟看论文——U-V-Disparity与地面检测、相机姿态估计

阳光穿透心脏的1/2处 2021-12-24 08:27 316阅读 0赞

# 菜鸟看论文——U-V-Disparity与地面检测、相机姿态估计 #

本文转载自：[https://www.oipapio.com/cn/article-4924327][https_www.oipapio.com_cn_article-4924327]  
部分PPT地址：[https://download.csdn.net/download/qq\_326324545/11260394][https_download.csdn.net_download_qq_326324545_11260394]  
首先，本部分ppt是由我的师妹王童鞋制作，此处应有掌声~![face0.gif][]

## 一、U-V-Disparity基础知识 ##

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注意，此处的（x,y,z）没有实际意义，其实是(u*Zc，v*Zc,Zc）的简写而已，所以求(u,v)时候需要经过下一步才行：  
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其中z=Zc。

## 二、地面估计 ##

参考：02.Real time obstacle detection on non flat road geometry through v-disparity representation  
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参考：  
15.Ground Segmentation and Occupancy Grid Generation Using Probability Fields  
05.U-V-Disparity: An efficient algorithm for Stereovision Based Scene Analysis  
示例2：  
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An assumption in our proposed system is that the stereo rig can only rotate in the pitch and yaw angle, q;f,and as such no angular rotation occurs in the roll direction  
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注意和上面的区别在于没有高度h的位移。  
Expanding (1) the image coordinates of a point P are:  
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The epipolar constraint reduces the search for corresponding pixels in the two images to a 1-D search problem along the epipolar line. The disparity d of the matched feature is thus calculated as:  
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Following the method presented in \[4\] Xp, Yp, Zp can be derived from ul , v and d as follows to get:  
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参考：03. A single framework for vehicle roll, pitch, yaw estimation and obstacles detection by stereovision  
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## 三、 相机姿态与几何 ##

参考：  
07.Global Correlation Based Ground Plane Estimation Using V-Disparity Image  
05.Obstacle Detection with Stereo Vision for Off-Road Vehicle Navigation

### 1.Pitch估计 ###

The behavior of the ground correlation line during a pitch variation is to oscillate, parallel to itself. Experimentally, we found out that the cameras height variation due to oscillation has neglectable effects.  
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其中，y，z都是是点（x,y,z）的相机坐标，而不是世界坐标，（u，v）是相机物理坐标，而不是相机像素坐标。高度是相机垂直于地面的高度，角度是相机与地面的夹角，高度和角度都是变化的。w是视差。从而得到v（图像物理坐标，而不是像素坐标）和视差（图像物理坐标，而不是像素坐标）的斜率公式：  
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Actually, for the ground correlation lines to be exactly parallel to each other, it should satisfy the conditions shown in Fig. 2. In this figure,the y axis intersects the ground plane through the point G, the distance(a) between camera and G is fixed, and all different ground planes pass through point G. In this situation, the ground plane can be represented as  
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At different pitch angles shown in Fig. 3, the slope of ground plane in V-disparity image will be different（此时，y不是恒定的，而h是恒定的）.  
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The changing ratio of g  
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approaches 0 when is small, and  
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For the ground correlation lines to be parallel with each other at different pitch angles, it only need to satisfy Eq. 11.Thus for a given 4w and certain pitch oscillation, we need to reduce s. In \[10\], the tilt angle is 8.5. In \[1\], the tilt angle is 7.73.  
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The change of slope is very small, the difference between the greatest slope and smallest slope is merely 0.0652, which is 1.17%. Thus the assumption that the ground correlation lines under different pitch angles are parallel, is valid.  
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可看出是三维空间的直线（不易求解）。

### 2.Roll估计 ###

#### （1）在v-disparity图中利用线性相关系数判定是否是直线，进而判定roll是否为0，如果接近于1，那么roll就是0，否则不为0 ####

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#### （2）利用上述公式，将pitch和roll的估计转换为p，q的估计，归根到底是p的估计 ####

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### 3.Yaw估计 ###

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## 参考 ##

02.Real time obstacle detection on non flat road geometry through v-disparity representation  
03.In-vehicle obstacles detection and characterization by stereovision  
03.A single framework for vehicle roll, pitch, yaw estimation and obstacles detection by stereovision  
13.Complex ground plane detection based on V-disparity map in off-road environment

[https_www.oipapio.com_cn_article-4924327]: https://www.oipapio.com/cn/article-4924327
[https_download.csdn.net_download_qq_326324545_11260394]: https://download.csdn.net/download/qq_326324545/11260394
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