A straight line on a navigation map using the mercator projection represents

Mercator projection which is type of map projection use straight line on maps to represent the a line of constant bearing

Explanation:

Mercator projection which is type of map projection use straight line on maps to represent the a line of constant bearing

Basically a projection in the map conserve meridian angles. meaning of this statement is that if constant angle is defines by some navigational path which is evaluated with respect to north, then that navigational path is referred as straight line all over the map

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