.03" 



FIGURE 3. READERS DIGITIZING BT POINTS CAN RECORD TEMPERATURES 

 AT EXTREMES WITHIN THE THICKNESS OF A STYLUS TRACE TO 

 PROVIDE AN ESTIMATE OF THE GRAPHICAL GRADIENT ANGLE 

 THAT VARIES FROM THE TRUE GRADIENT ANGLE BY AS MUCH 

 AS PLUS OR MINUS 33°. 



(a) 



(b) 



(c) 



FIGURE 4. TWO READERS DIGITIZE POINTS FALLING WITHIN THE THICKNESS OF 

 THE SAME STRAIGHT STYLUS TRACE. L^ IS THE REGRESSION LINE ON 

 THE FIRST DATA SET (a), and L2 IS THE REGRESSION LINE ON THE 

 SECOND DATA SET (b). THE RESULTS ARE SUPERIMPOSED (c) TO 

 ILLUSTRATE THAT THE REGRESSION LINES L] AND Lj WILL TEND TO 

 AGREE MORE CLOSELY, DEPTH FOR DEPTH, THAN THE ORIGINAL 

 DATA POINTS. 



