AMCL pose being updated while robot drifts

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Hi All,

I am using ROS Kinetic on Ubuntu 16.04.

I tried to see how drifting/slipping of robot wheels effect /amcl_pose and /pose topics in my rosbot. when I placed the rosbot on a elevated platform and sent telep commands. I saw that /pose topic was being updated because it relies on /odom data. But I noticed that /amcl_pose also being updated which I did not expect.

I was thinking amcl will use scan matching on a given map to localize it's position. can anyone explain why the error is happening and How actually amcl works.

Thanks in Advance.