Exploring Earth

We humans live on a 3D spherical planet. The cartographer's main challenge is how to express the 3D  planet into a 2D  flat surface. One of the projection of map is called Mercator projection, where the continents are projected into a cylinder. Then the cylinder is split and flattened. There are totally six projections, which are mercator projection, sinusoidal projection, robinson projection, peters projection, miler projectionm and orthographic projection.