Kitti

Understanding the Calibration file

This file basically contains all the transform between between different frames of camera such as velodyne, camera, etc.

Use following links to understand it:

3MB

Kitti.pdf

pdf

Kitti official Data Discription

KITTI 3D Object Detection DatasetMedium

Main equation for transformation

$$y = P_{rect}^i x^{rect}$$

In the calib.txt file, the $P_0, P_1, P_2, P_3$matrices are the projection matrix which project the 3D point $x_{rect}$in rectified camera coordinate frame to image coordinates of camera $i$. Please note that rectified camera coordinate frame is not related to any camera $i$. So basically these $P_i$given in calib.txt are actually$P_{rect}^i$ and takes points in rectifies camera coordinate and not points in $i^{th}$camera coordinate frames.

$$y = P_{rect}^i R_{rect}^0 Tr^{velo-to-cam0} x^{velo}$$

This is one of the main equation given in the readme.md file for transformations of points. Here $x^{velo}$is 3D point in velodyne coordinate frame. $Tr^{velo-to-cam0}$ transform an point from velodyne to reference camera (cam0) coordinate frame. ie. $x^{cam0} = Tr^{velo-to-cam0}x^{velo}$. $x^{cam0}$is in cam0 coordinate frame, cam0 is reference camera in kitti.

$$x^{rect}= R_{rect}^0x^{cam0}$$

We need $x$in rectified frame to be worked with $P_{rect}^i$. Hence we use $R_{rect}^0$which transform point from cam0 coordinate frame to rectified coordinate frame.

Different Packages for using Kitti Dataset

Python Package to read Kitti data.

GitHub - utiasSTARS/pykitti: Python tools for working with KITTI data.GitHub

Covert Kitti dataset to ROS Bag or Publish as ROS topics.

GitHub - tomas789/kitti2bag: Convert KITTI dataset to ROS bag file the easy way!GitHub