The CTP-1 is a handy Time Scale for rapid Groundspeed & ETA Calculations. Manufactured in white card 215mm x 70mm size. Sliding Scale measures distance flown in Nautical Miles, Statute Miles or Kilometres off 1:500,000 VFR Charts. Window then displays average Ground Speed in Knots, Miles per hour and kilometres per hour. Reverse incorporates Sliding Scale indications of Distance off Course and Degree of Error for Distance flown.