local map subtraction for moving object detection

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Hi all,

I am new in ROS and I am going to do a subtraction between a current laser measurement map at time t and time t-1 for moving object detection. the procedure is as follow:

1. Convert laser measurement at time t to 2d grid form that contain free and occupied cells (I call it laser measurement map).
2. Limit this (2d grid) laser measurement map in a rectangle with edge size of lets say 5 meters. So the robot can see 2.5 meters ahead, back, left and right.
3. Next, I am going to do a subtraction between a current laser map at time t and laser map provided at time t-1. (each laser map associated with odometry data, so the laser measurement map provided at time t-1 will be projected on laser measurement map at time t, and subtraction is done in the joint area).

Could you please guide me how to do it with already available packages in ROS? I found two related packages: costmap_2d and Gmapping. I don't know if there is better packages available to use? Based on your experience which one has a potential to use for this purpose? What steps should I take to do it?

Thanks.