菜鸟看论文——U-V-Disparity与地面检测、相机姿态估计

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

首先，本部分ppt是由我的师妹王童鞋制作，此处应有掌声~

一、U-V-Disparity基础知识

 
 

 

 

 

 

 

 

 

 

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：

 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

 

 

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：

   

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

 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:

 

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:

Following the method presented in [4] Xp, Yp, Zp can be  derived from ul , v and d as follows to get:

 

参考：

03.A single framework for vehicle roll, pitch, yaw estimation and obstacles detection by

stereovision

 

 

 

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.

 

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：

 

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

 

 

  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）.

 

 The changing ratio of g

   approaches 0 when is small, and

 

 

  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.

 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.

 

 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

 

 

 （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

 

 

 3.Yaw估计