path planning without using an already made map

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I need to control (path planning) a robot without sensing environment by any sensor. I mean without using a prepared map. To do this, I need to set a starting coordination, an end point and coordination of obstacles, then to find the shortest collision-free path by the use of a simple algorithm under ROS environment (A ROS node that calculates the shortest path and command the robot to traverse). Dose anybody have any idea how to: 1- Create a so-called hand-made map under ROS package application. 2- make understand the robot that it has a path ahead without a map?

What else do I need to consider for this simple test? Do I need a special already made ROS package?

I am open to any suggestion, link and information. Thanks,