一种适用于极区的横轴墨卡托海图

极区位于高纬度地区,极区航海图投影采用墨卡托投影时,图上极区附近变形较大,在极点处变形达到无穷大;采用极球面投影时,图上恒向线不是直线;心射切面投影不是正形投影,不能直接在图上量取方位和距离;兰伯特正形投影图上,经度是由角度表示,而不是真的经度;采用横轴墨卡托投影时,几乎所有的经线以及纬线在图上为曲线。以上常用的海图投影不利于船舶在极区安全航行,也不利于航海人员进行海图作业。针对此问题,将构建的伪经纬线网与经纬线网进行转换,通过Matlab得到基于伪经纬线网的横轴墨卡托投影图,此图具有类似于墨卡托海图的特点,图上极区变形失真小,图上伪经纬线的特点可方便极区海图作业。

A transverse Mercator chart suitable for polar regions

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.