Text original - Anglès - The projections discussed previously are...

The projections discussed previously are conceptually created by projecting from one geometric shape (a sphere) onto another.
many projections are not related as easily to a cone, cylinder, or plane.
modified projections are altered versions of other projections (e.g., the space oblique mercator is a modification of the mercator projection.)
this modifications are made to reduce distortion, often by including additional standard lines or changing the distortion pattern.