10 



NAUTICAL CHART MANUAL 



Compass roses should be located on the chart so as to be convenient to the most important 

 navigational areas, and at such intervals that any part of the water area is within the reach 

 of a parallel ruler. In some cases it will be necessary to remove topographic features when 

 compasses are placed on land areas. In no case should compasses be so placed as to cover or 

 even be close to any danger in the water area. They should not be placed at the entrance to 

 a harbor. When placed in the water area, every effort must be made to see that soundings 

 do not fall on the graduations or figures. A new selection of soundings must be made if necessary. 



Compass roses shall be printed in magenta. On loran charts on which one rate is in 

 magenta, the compasses shaU be printed in black. 



In general, on charts showing isogenic lines, the compass rose shall consist of a compass 

 circle with zero at true north, and a centerline oriented in accordance with the direction and 

 amount of variation. Along this line should be shown the amount of variation, the year 

 determined (in parentheses) and the annual change. Variations shall be given in units of 

 15' only. 



Compass Rose for Charts with Isogonic Lines 



LOCAL MAGNETIC DISTURBANCE 



Local magnetic disturbance, which causes noticeable deflections of the compass, is a fairly 

 common occurrence in shallow water and in proximity to mountain masses. It is believed that 

 disturbances need not be considered in depths greater than 500 fathoms. Notes in magenta 

 calling attention to local magnetic disturbance should be placed on the charts. These notes 

 should be based on information furnished by the Division of Geomagnetism. (Fig. 13) 



