What is difference between Head up display and North up display?

Head up Display
North up Display
  1. Picture smudges in azimuth. During alterations of course.
  2.  Because of smudging, accurate bearing cannot be taken during large co alteration.
  3. Plotting became highly inaccurate during yow in bad weather as ships heads changing several degrees per sec, resulting in severe smudging.
  4.  All bearings are relative.
  5.  Time wasted in conversion of relative bearing into true bearings.
  6.  Chances of electrical error in conversion from relative to true bearings.
  7. Radar picture is head up where as the chart is north up.
  8.  After large alterations of course observer tends to get disoriented with plotting as all targets have shifted to the new relative bearing on the radar screen.
  9. No indication, on PPI of gyro Course steered. Temporary alterations or wandering off course can remain forgetter unless the compass repeater or Course recorder is inspected.
    1.  ARPA cannot be used.
  1. Picture does not smudge during alteration of co.
  2.  Baring can be taken accurately, even during large alterations of course.
  3. Plotting accuracy unaffected by yaw.
  4. All bearings are true.
  5. No such time lost as true bearings are directly obtained.
  6.  No such chances of electrical error as true bearings are directly obtained.
  7. Both being north up, easier comparison with the chart.
  8.  No such disorientation as all targets remain on their true bearings on the radar screen, despite large alterations of course.
  9. Heading marker indicates at all times, the gyro course steered. Every time the observer inspects the radar screen, the Course Steered gets checked by him.
  10. ARPA can be used.