The convergence of geographic meridians at the Arctic Ocean makes steering and positioning extremely difficult when utilizing conventional inertial navigation system (INS) on board. The polar grid navigation method based on great-circle sailing is presented to cope with above problems. The characteristics of map projection in the polar region are compared, and the polar stereographic projection is chosen to be the polar chart projection. The polar grid navigation method which takes the Greenwich meridian as the reference meridian is presented. The course error caused by the approximate straight line representation of the great circle is expounded in detail. Theory analysis indicates that ship navigation accuracy will not be influenced by the approximate straight line representation of the great circle. The polar grid navigation adopted in the great-circle sailing can provides the accurate position information.%为了克服因极区地理经线快速收敛而产生的惯导系统无法准确定位的难题，提出基于大圆航行的极区格网导航方法。分析几种投影方式在标绘极区海图中的表现，选择极球面投影作为极区海图投影方式，将本初子午线作为格网北的极区格网导航方法，并详细分析当海图上的大圆被表示为直线时所产生的航向误差。理论分析证明：将大圆近似表示为直线对于航向误差不会产生任何影响，在大圆航行中采用格网导航方法是可行有效的，能够为船舶航行提供精确的位置信息。
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