How to make robot localise itself its initial point with existing map

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Hi there,

I want to make my robot autonomously localise itself at the starting point (which could be anywhere in a room) then send some navigation goals for it to follow, then at the end i want my robot to return to the same initial point which it had localised itself in the beginning, all without any user intervention. I have already created map with GMapping and text labels for each point.