© 2006 Carnegie Mellon Robotics Academy Designed for use with the LEGO MINDSTORMS ® Education NXT Software and Base Set #9797 Mine Mapping Scanning and Mapping See Teacher Guide for printing instructions

© 2006 Carnegie Mellon Robotics Academy Designed for use with the LEGO MINDSTORMS ® Education NXT Software and Base Set #9797 Opening Activity You are trapped in a dark room with only a small flashlight, a pen, and some paper. Using only these tools, come up with a way to describe the layout of the room to someone who has never seen it before.

© 2006 Carnegie Mellon Robotics Academy Designed for use with the LEGO MINDSTORMS ® Education NXT Software and Base Set #9797 Opening Activity Since you can only see a little bit of the room at a time, you have to record data in pieces, then put them back together at the end. This is called scanning.

© 2006 Carnegie Mellon Robotics Academy Designed for use with the LEGO MINDSTORMS ® Education NXT Software and Base Set #9797 Opening Activity You must then reassemble the data into a physical facsimile of the actual room. The end result represents the room, but obviously is not the room itself. This is called mapping.

© 2006 Carnegie Mellon Robotics Academy Designed for use with the LEGO MINDSTORMS ® Education NXT Software and Base Set #9797 Mapping Maps must choose carefully what data they wish to represent. Somewhere In There… This map tries to represent too much information at once (some of which is not very important at all) X Marks the Spot Representing only the most important data allows a reader to focus on the parts of the information that matter most

© 2006 Carnegie Mellon Robotics Academy Designed for use with the LEGO MINDSTORMS ® Education NXT Software and Base Set #9797 Floor Plan Map Represents the rough layout of a room-like space at or near ground level Shows: –Walls –Objects of significant size –Everything as close to real scale as possible Does not show: –Heights –Small or easily moveable objects Is this suitable for mapping the inside of a tunnel or mined-out room? Floor Plan Walls and significant objects shown, drawn to scale

© 2006 Carnegie Mellon Robotics Academy Designed for use with the LEGO MINDSTORMS ® Education NXT Software and Base Set #9797 Polar Coordinates When looking around, it’s convenient to be able to stand in one spot and record an object’s position according to its distance and direction. The polar coordinate system is ideal for this. Observer and Object The most natural way to express the location of an object is by saying which direction it’s in, and how far away 1.5m

© 2006 Carnegie Mellon Robotics Academy Designed for use with the LEGO MINDSTORMS ® Education NXT Software and Base Set #9797 Polar Coordinates A position in polar coordinates is simply: (distance, direction) –A distance, how far away the object is from the observer –A direction, measured in how many degrees you have to turn to face the object Note that the angle is measured in degrees starting with 0 on the far right –Avoids confusion between left and right (“45 degrees to the left or 45 degrees to the right?”) –No need to use negative numbers for directions (though you could if you wanted to) Polar Graph Polar coordinates are based around direction and distance from an observer

© 2006 Carnegie Mellon Robotics Academy Designed for use with the LEGO MINDSTORMS ® Education NXT Software and Base Set #9797 Polar Coordinates The shape of points on the graph is still the same shape in the end! Polar coordinates are simply a different way of writing locations, the space they represent is the same as Cartesian (x,y) coordinates! Points in Polar Points in CartesianPoints with no coordinates = =

© 2006 Carnegie Mellon Robotics Academy Designed for use with the LEGO MINDSTORMS ® Education NXT Software and Base Set #9797 View Mode Scanning & Mapping: Technical Review

© 2006 Carnegie Mellon Robotics Academy Designed for use with the LEGO MINDSTORMS ® Education NXT Software and Base Set #9797 View Mode Displays a sensor value on the NXT’s LCD screen Updates continually View Mode The View Mode on the NXT allows you to read sensor values without needing to write a program first

© 2006 Carnegie Mellon Robotics Academy Designed for use with the LEGO MINDSTORMS ® Education NXT Software and Base Set #9797 Since you can only see a little piece of the puzzle at a time, you will need to scan the room and take many readings, then construct a map to organize and represent the space. Polar coordinates allow you to construct a simple 2D map by simply specifying the distance and direction to locations of interest Summary You must develop a working method for interpreting sensor readings into maps You will use the NXT’s View Mode to monitor sensor values while experimenting