Do not use map pins, needles, ink pens or grease pencils. Using these items will damage the
board. Plotting should be done with a very sharp, soft lead pencil (No. 2 or softer). Be careful
when placing a plot on the disk, for a very small plotting error could cause the final data to be
off as much as 25 meters in range and more than 10 mils in deflection. To avoid distortion, you
should place your eye directly over the location of a point and hold your pencil perpendicular to
the board. The plot should be so small that it is difficult to see. For ease of identification, circle
and number each plot.