Why can the odom frame drift?

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Hi there!

As I understand, the drift mentioned on REP 105 refers to the fact that the difference between the pose of the robot on the real world and the estimated pose of the robot by the odometry (lets call this odometry error) will grow over time due the well-known problems of odometry calculation. For example:

• Small difference between the nominal and actual wheel diameter -> will cause the odometry error to grow over time
• Small difference between the nominal and actual tread -> will cause the odometry error to grow over time
• Wheel slipping -> will cause the odometry error to grow over time
• No matter what you do -> the odometry error will grow over time

Regarding the continuity of the odom frame, yes, you should avoid big jumps. The values on the odom frame should be continuous, and any compensation for the odometry error (drift) should be made on the map frame:

In a typical setup, a localization component constantly re-computes the robot pose in the map frame based on sensor observations, therefore eliminating drift, but causing discrete jumps when new sensor information arrives.