关键词: 极区航海, 伪经纬线网, 航海图, 横轴墨卡托投影, 海图切换

Abstract:

Polar regions are located at high latitudes. And tThere may be several choices for chart projection of polar regions, including Mercator projection, polar stereographic projection, gnomonic projection, Lambert conformal projection and transverse Mercator projection. The Mercator projection introduces an increasingly large deformation near the polar regions and deformation of infinity at the poles on the chart. With polar stereographic projection, the rhumb line is not straight on the chart. Gnomonic projection is not conformal projection, therefore, it is very difficult to measure range and bearing directly on the chart. On a Lambert conformal chart, longitude is represented by angle. With the transverse Mercator projection, almost all lines of latitude and longitude are curved. Hence, none of the aforementioned projection is particularly suitable for safe polar navigation and reliable chart work. To solve the above problems, a false graticules is constructed and the problem of transforming between false and true latitude and longitude is solved. A transverse Mercator chart based on this false graticules is drawn using MATLABatlab. The characteristics of this new type of chart are similar to those of a Mercator chart and there is still deformation distortion in the polar region, but lines of false longitude and false latitude are mutually parallel and respectively orthogonal. Overall, this new type of chart would be convenient for doing polar chart work.

Key words: polar navigation, false graticules, navigation chart, transverse Mercator projection, chart change