readme.txt

###########################################################################
#            THE KITTI VISION BENCHMARK SUITE: OBJECT BENCHMARK           #
#              Andreas Geiger    Philip Lenz    Raquel Urtasun            #
#                    Karlsruhe Institute of Technology                    #
#                Toyota Technological Institute at Chicago                #
#                             www.cvlibs.net                              #
###########################################################################

This file describes the KITTI object detection and orientation estimation
benchmarks, consisting of 7481 training images and 7518 test images for each
task. Despite the fact that we have labeled 8 different classes, only the
classes 'Car' and 'Pedestrian' are evaluated in our benchmark, as only for
those classes enough instances for a comprehensive evaluation have been
labeled. The labeling process has been performed in two steps: First we
hired a set of annotators, to label 3D bounding boxe tracklets in point
clouds. Since for a pedestrian tracklet, a single 3D bounding box tracklet
(dimensions have been fixed) often fits badly, we additionally labeled the
left/right boundaries of each object by making use of Mechanical Turk. We
also collected labels of the object's occlusion state, and computed the
object's truncation via backprojecting a car/pedestrian model into the
image plane.

NOTE: WHEN SUBMITTING RESULTS, PLEASE STORE THEM IN THE SAME DATA FORMAT IN
WHICH THE GROUND TRUTH DATA IS PROVIDED (SEE BELOW), USING THE FILE NAMES
000000.txt 000001.txt ... CREATE A ZIP ARCHIVE OF THEM AND STORE YOUR
RESULTS (ONLY THE RESULTS OF THE TEST SET) IN ITS ROOT FOLDER.

NOTE2: Please read the bottom of this file carefully if you plan to evaluate
results yourself on the training set.

Data Format Description
=======================

The data for training and testing can be found in the corresponding folders.
The sub-folders are structured as follows:

  - image_02/ contains the left color camera images (png)
  - label_02/ contains the left color camera label files (plain text files)
  - calib/ contains the calibration for all four cameras (plain text file)

The label files contain the following information, which can be read and
written using the matlab tools (readLabels.m, writeLabels.m) provided within
this devkit. All values (numerical or strings) are separated via spaces,
each row corresponds to one object. The 15 columns represent:

#Values    Name      Description
----------------------------------------------------------------------------
   1    type         Describes the type of object: 'Car', 'Van', 'Truck',
                     'Pedestrian', 'Person_sitting', 'Cyclist', 'Tram',
                     'Misc' or 'DontCare'
   1    truncated    Float from 0 (non-truncated) to 1 (truncated), where
                     truncated refers to the object leaving image boundaries
   1    occluded     Integer (0,1,2,3) indicating occlusion state:
                     0 = fully visible, 1 = partly occluded
                     2 = largely occluded, 3 = unknown
   1    alpha        Observation angle of object, ranging [-pi..pi]
   4    bbox         2D bounding box of object in the image (0-based index):
                     contains left, top, right, bottom pixel coordinates
   3    dimensions   3D object dimensions: height, width, length (in meters)
   3    location     3D object location x,y,z in camera coordinates (in meters)
   1    rotation_y   Rotation ry around Y-axis in camera coordinates [-pi..pi]
   1    score        Only for results: Float, indicating confidence in
                     detection, needed for p/r curves, higher is better.

Here, 'DontCare' labels denote regions in which objects have not been labeled,
for example because they have been too far away from the laser scanner. To
prevent such objects from being counted as false positives our evaluation
script will ignore objects detected in don't care regions of the test set.
You can use the don't care labels in the training set to avoid that your object
detector is harvesting hard negatives from those areas, in case you consider
non-object regions from the training images as negative examples.

The coordinates in the camera coordinate system can be projected in the image
by using the 3x4 projection matrix in the calib folder, where for the left
color camera for which the images are provided, P2 must be used. The
difference between rotation_y and alpha is, that rotation_y is directly
given in camera coordinates, while alpha also considers the vector from the
camera center to the object center, to compute the relative orientation of
the object with respect to the camera. For example, a car which is facing
along the X-axis of the camera coordinate system corresponds to rotation_y=0,
no matter where it is located in the X/Z plane (bird's eye view), while
alpha is zero only, when this object is located along the Z-axis of the
camera. When moving the car away from the Z-axis, the observation angle
will change.

To project a point from Velodyne coordinates into the left color image,
you can use this formula: x = P2 * R0_rect * Tr_velo_to_cam * y
For the right color image: x = P3 * R0_rect * Tr_velo_to_cam * y

Note: All matrices are stored row-major, i.e., the first values correspond
to the first row. R0_rect contains a 3x3 matrix which you need to extend to
a 4x4 matrix by adding a 1 as the bottom-right element and 0's elsewhere.
Tr_xxx is a 3x4 matrix (R|t), which you need to extend to a 4x4 matrix 
in the same way!

Note, that while all this information is available for the training data,
only the data which is actually needed for the particular benchmark must
be provided to the evaluation server. However, all 15 values must be provided
at all times, with the unused ones set to their default values (=invalid) as
specified in writeLabels.m. Additionally a 16'th value must be provided
with a floating value of the score for a particular detection, where higher
indicates higher confidence in the detection. The range of your scores will
be automatically determined by our evaluation server, you don't have to
normalize it, but it should be roughly linear. If you use writeLabels.m for
writing your results, this function will take care of storing all required
data correctly.

Object Detection Benchmark
==========================

The goal in the object detection task is to train object detectors for the
classes 'Car', 'Pedestrian', and 'Cyclist'. The object detectors must
provide as output the 2D 0-based bounding box in the image using the format
specified above, as well as a detection score, indicating the confidence
in the detection. All other values must be set to their default values
(=invalid), see above. One text file per image must be provided in a zip
archive, where each file can contain many detections, depending on the 
number of objects per image. In our evaluation we only evaluate detections/
objects larger than 25 pixel (height) in the image and do not count Vans as
false positives for cars or Sitting Persons as wrong positives for Pedestrians
due to their similarity in appearance. As evaluation criterion we follow
PASCAL and require the intersection-over-union of bounding boxes to be
larger than 50% for an object to be detected correctly.

Object Orientation Estimation Benchmark
=======================================

This benchmark is similar as the previous one, except that you have to
provide additionally the most likely relative object observation angle
(=alpha) for each detection. As described in our paper, our score here
considers both, the detection performance as well as the orientation
estimation performance of the algorithm jointly.

Mapping to Raw Data
===================

Note that this section is additional to the benchmark, and not required for
solving the object detection task.

In order to allow the usage of the laser point clouds, gps data, the right
camera image and the grayscale images for the TRAINING data as well, we
provide the mapping of the training set to the raw data of the KITTI dataset.

This information is saved in mapping/train_mapping.txt and train_rand.txt:

train_rand.txt: Random permutation, assigning a unique index to each image
from the object detection training set. The index is 1-based.

train_mapping.txt: Maps each unique index (= 1-based line numbers) to a zip
file of the KITTI raw data set files. Note that those files are split into
several categories on the website!

Example: Image 0 from the training set has index 7282 and maps to date
2011_09_28, drive 106 and frame 48. Drives and frames are 0-based.

Evaluation Protocol:
====================

For transparency we have included the KITTI evaluation code in the
subfolder 'cpp' of this development kit. It can be compiled via:

g++ -O3 -DNDEBUG -o evaluate_object evaluate_object.cpp

IMPORTANT NOTE:

This code will result in 41 values (41 recall discretization steps). However,
note that in order to compute average precision, we follow the PASCAL protocol
and average by summing in 10% recall steps. The pseudocode for computing average
precision or orientation similarity is given as follows:

sum = 0;
for (i=0; i<=40; i+=4)
  sum += vals[i];
average = sum/11.0;