Magnetic Variation for the area concerned can be set, and the horizontal or vertical lines on the disc are then lined up with any Latitude or Longitude meridian on the chart.
Ukuguqu-guquka okunomtsalane kwindawo ekujongenwe nayo kungaqulunqwa, kwayo okhwezayo nehlileyo imigca kwimba wendaba ziphinda zidweliswe ngokobude okanye ububanzi bencopho yesikhankanyi esibhakabhakeni kwitshati.