requirement for security of command and control and for this reason recent advances in


communications such as wireless Ethernet that are typically omni-directional are not


considered.


 This work is based on the premise that the robots must maintain line-of-sight in order


to communicate with a base station or another robotic entity. Therefore, initial steps were


taken to develop an algorithm that determines if line-of-sight exists between two robots.


 Line of sight is determined for two robots whose positions are known. Simply put, it


is necessary to determine if a line segment drawn between the two robots intersects any


of the known obstacles. With the grid-based approach, this can be done rapidly by


starting at robot l's position and then moving to the next adjacent grid position that


moves closer to robot 2's position. A start angle startr) is calculated based on the (x,y)


positions of the two robots. The current angle currentn) is initialized to the start angle and


the current position (xc,yc) is initialized to the position of robot 1. The value of the

 90 North






 Robot 2
 (x2,y2)

 180 West 0 O0 East


 start angle

 Robot 1
 (xlyl)

 III IV
 270 South

 Figure 2.4: Illustration of line-of-sight method