how to localize my robot

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thank you...i went through this tutorials.i applied this to turtlebot rosrun amcl amcl but it is showing that request for map failed.

If you are you using gmapping, try set the param "use_map_topic" to true, this way the amcl node will read the information from the topic /map published by gmapping. To do this adding the following line in your launch should be enough:

 <param name="use_map_topic " value="true" />

Or if you want to do a rosrun directly this should work:

rosrun amcl amcl _use_map_topic:=true

I did rosrun amcl amcl _use_map_topic:=true. I got map also but how can i find the grid in which the robot resides so that i can apply my A* algorithm.

As you can see in the wiki documentation, the map is published in the /map topic, in the type of message Occupancy grid, while the pose of the robots is published in the topics /amcl_pose.

You should then, just subscribe/publish to that topics and use that information, for that the following tutorial could help you. Tutorial

thank you sir..But when i do the same i'm getting the x,y coordinates of the robot in its current position. I want to know the index of the grid in which the robot is situated in the map so that I can apply my A* algorithm. Could you please help me to solve this problem.?

Hi! Right now i am not quite sure about how to exactly doing that. What i know is that gmapping publish a map in the format of a occupancygrid msg see the msg documentation.