Frequently asked Questions

Can I ignore all the other files but only use map.cirles for range-bearing case and only use map.lines for bearing only case?

Yes. All the other files are mostly for visualization. The Python code is just for convenience. In the map.lines and map.circles files everything is already in robot coordinates and no further processing is nessecary (for example cameras model etc) but if you would like to visualize something, maybe the camera model in the "sensormodel" directory can help.

What is the meaning when the landmark ID is -1?

It's not assigned. Some measurement are just reflections or are only once seen by the landmark extractor. These landmarks are then irgnored but stored as -1 in the data files.

For the line case, you said: {alpha, beta} is the angle of the observation in robot coordinates. Why are there two angles? What acutally is the unit?

What you would use for data association is the alpha angle. It's the angle in respect to the robot coordinate system. The unit is radian.
Beta is the angle in respect to a vertical line. So not very useful. But if you can use it for anything that would be okay.

The quality values in the lines set are all 0. Why is that?

The format was from an old export and we didn't change it. We added the sigma_alpha value, which gives you information about the uncertainty of the landmark.