67


equation of the line. Using this as the point of origin, the distance, a, can be found to the

point (x,y), which corresponds to the current location of the sensor.



 (x,y) a -


 XX
 Y




 d


 SStair Riser



Figure B-3: Stair riser model

 The equation for this distance is shown in Equation B-1. Through the similar

triangles concept, the angle, 0, is shown on the two locations of Figure B-3. The angle, y,

is the user-defined angle of the infrared sensor. Using y and 0, the angle, T, may now be

found by:

 =r-P (B-5)


The distance, f, is defined as:


 f = a cos

Finally, the distance, d, may be found by:


 d =
 COS Z


(B-6)


(B-7)