Pre Calibration File Configuration

File Configuration

This section describes how to configure a few OpenPTrack files that will allow each node to communicate properly across the network, and identify their associated imager.

1. Modify the .bashrc.

Every sensor should be connected to a PC on the same Gigabit Ethernet network. One PC will be the master, where the calibration code and the tracking code will run, while the other PCs will run the sensor drivers (during calibration) and the people detection code (during distributed detection and tracking). To allow communication between software nodes in different computers, the environment variable ROS_MASTER_URI on every client PC must be set to the IP address of the master PC. Additionally, the ROS_IP and ROS_PC_NAME environment variables must be set on every PC. This can be done temporarily on a terminal by typing the following commands:

 export ROS_MASTER_URI=http://<MASTER_IP>:11311/
 export ROS_IP=<MACHINE_IP>
 export ROS_PC_NAME=<MACHINE_NAME>

For example:

 export ROS_MASTER_URI=http://192.168.100.101:11311/
 export ROS_IP=192.168.100.102
 export ROS_PC_NAME=PC1-Example

Note that the PC names to be assigned can be whatever the user wants, not necessarily related to the real name of the PCs. To set them definitively, they can be added directly to the end of the .bashrc file in the home folder by typing:

 echo "export ROS_MASTER_URI=http://192.168.100.101:11311/" >> ~/.bashrc
 echo "export ROS_IP=192.168.100.102" >> ~/.bashrc
 echo "export ROS_PC_NAME=PC1-Example" >> ~/.bashrc

or:

 gedit ~/.bashrc

If gedit is used, the same variables need to be set in the bashrc file:

 ROS_MASTER_URI=http://192.168.100.101:11311/
 ROS_IP=192.168.100.102
 ROS_PC_NAME=PC1-Example

2. Create files for multi-sensor calibration.

Multi-sensor calibration is performed by running a calibration node in the master PC and a sensor driver in every PC attached to a sensor (one driver node for every sensor). The network must be configured in the opt_calibration/conf/camera_network.yaml file.

First, make that file.

Below is a camera_network.yaml file for a network composed of two PCs with two sensors each:

# Camera network parameters
network:
  - pc: "PC1-Example"
    sensors:
      - type: kinect1
        id: "Kinect_Left"
        serial: "A00364820345039A"
      - type: kinect1
        id: "Kinect_Right"
        serial: "A00345482325021B"
  - pc: "PC1-Example"
    sensors:
      - type: kinect2
        id: "Kinect_PC2"
      - type: sr4500
        id: "SwissRanger"
        ip: "192.168.1.42"
      - type: stereo_pg
        id: "blackfly_stereo"
        serial_left: "13310958"
        serial_right: "13310959"

N.B.: Pay particular attention to the leading spaces. Do not use Tab.

N.B.2: In the opt_calibration/conf/camera_network.yaml:

   - pc: "PC1-Example"

needs to match the .bashrc:

  ROS_PC_NAME=

A PC is added to the network with the parameter pc: "<ROS_PC_NAME>" preceded by a minus that indicates that it belongs to a list (see yaml documentation above).

Then, for each PC, the list of the connected sensors is added with the parameter sensors. For each sensor, two to four parameters can be defined:

• type (mandatory) defines the type of the sensor. It must be kinect1 for the 1st Kinect version, kinect2 for the 2nd Kinect version, sr4500 for Swiss Rangers SR4500, and stereo_pg for custom stereo pairs composed of Point Grey cameras.
• id (mandatory) is the unique name to identify the sensor in the network.
• serial (optional, for Kinects only) defines the serial number of the Kinects to make them distinguishable in the same PC.
• ip (mandatory, for SwissRangers only) is the local IP address of the SwissRanger (can be the same for each one if connected to different PCs).
• serial_left, serial_right (optional, for stereo only) define the serial numbers of the left and right cameras of the stereo pair. The serials of the cameras attached to a PC can be retrieved with rosrun pointgrey_camera_driver list_cameras.

The parameters of the checkerboard used for calibration must also be added:

# Checkerboard parameters
checkerboard:
  rows: 6
  cols: 5
  cell_width: 0.12
  cell_height: 0.12

Note: The rows and cols parameters are defined by the number of chess intersections in rows and columns (cols), not the number of squares along the edge of the checkerboard. The width and height measurements are in meters.

For example:

In the image above, the rows count is 6, and the cols count is 5. This is due to the intersections of columns and rows on the checkerboard. An easy way to think about this is to count the columns and rows and subtract 1 from each of the counts. In the checkerboard above, there are 7 rows and 6 cols; subtracting 1 from each gives us the value required for calibration configuration, for 6 rows and 5 cols.