Install ethzasl_ptam to ROS

Installing additional libraries

#OpenGL and linear algebra library:  
sudo apt-get install freeglut3-dev libatlas-base-dev  

Install ETHZASL_PTAM

# create and enter stack directory:  
mkdir ~/ros  
cd ~/ros  
   
# Fetch ethzasl_ptam stack  
git clone git://github.com/ethz-asl/ethzasl_ptam.git ethzasl_ptam  
   
# Update ROS_PACKAGE_PATH for this session
export ROS_PACKAGE_PATH=$ROS_PACKAGE_PATH:~/ros/ethzasl_ptam

# Update ROS_PACKAGE_PATH for every session
echo -e '\n\n#ethzasl_ptam ROS path:\nexport ROS_PACKAGE_PATH=$ROS_PACKAGE_PATH:~/ros/ethzasl_ptam' >> ~/.bashrc 
   
# Install system dependencies (in case some still is missing)  
rosdep install ptam  
   
# build  
rosmake ethzasl_ptam  

Using ETHZASL_PTAM with ARDrone2

Modify the image details in cameracalibrator.launch as such:

...
        <remap from="image" to="/ardrone/front/image_raw" />   
...

Edit command:

nano ~/ros/ethzasl_ptam/ptam/launch/cameracalibrator.launch  

For ptam.launch:

...
        <remap from="image" to="$(optenv IMAGE /ardrone/front/image_mono)" />  
...

Edit command:

 nano ~/ros/ethzasl_ptam/ptam/launch/ptam.launch  

Calibrating the ARDrone2 camera

Print ~/ros/ethzasl_ptam/ptam/calib_pattern.pdf. It is a chessboard used to estimate the focal length of the camera.

Now start ROS and launch the calibrator:

#In one console start ROS:
roscore
#in another console
roslaunch ptam cameracalibrator.launch  

Now "grab" around 10 frames, then press "optimize" and "save".

Saving calibration values

Using the output values of the cameracalibrator, update PtamFixParams.yaml:

#edit the image size and Camera   
nano ~/ros/ethzasl_ptam/ptam/PtamFixParams.yaml  

As such:

#ARDrone2 default camera resolution:  
ImageSizeX: 640  
ImageSizeY: 360  
   
...  
...  
   
#ARDrone2 camera intrinsic calibration values  
Cam_fx: first value (normalized focal length in x)  
Cam_fy: second value (normalized focal length in y)  
Cam_cx: third value (normalized camera center in x)  
Cam_cy: fourth value (normalized camera center in y)  
Cam_s: fifth value (normalized distortion factor, <1 for wide FoV)  

Running it

Locally:

#start ROS in one console  
roscore  
   
#Start the ARDrone2 streaming (publishes the image/camera topics). In another console:  
rosrun ardrone_autonomy ardrone_driver _realtime_navdata:=True _navdata_demo:=0  
   
#Use image_proc to convert to grayscale. In another console:  
ROS_NAMESPACE=/ardrone/front rosrun image_proc image_proc  
   
#Launch ETHZASL_PTAM in another console:  
roslaunch ptam ptam.launch  

Remotely:

Edit PtamFixParams.yaml to not run the GUI:

Gui: False

Next, start ptam and on the same machine or a different one that has the correct ROS_MASTER_URI, run:

#image stream  
rosrun ptam remote_ptam  
   
#3D cloud stream  
rosrun ptam ptam_visualizer

References

ethzasl_ptam - ROS Wiki
ethzasl_ptam/Tutorials/using_ethzasl_ptam - ROS Wiki
ethzasl_ptam/Tutorials/camera_calibration - ROS Wiki
ethzasl_ptam/Tutorials/remote_ptam - ROS Wiki