2D Map Projections — Mercator vs Mollweide vs Orthographic (2D)

Projection

Main projection

Layers

Drag the map to recentre it: rotates the globe under Orthographic/Stereographic, shifts the central meridian under Equirectangular/Mercator/Mollweide.

Area scale ≈ 1 (true to the sphere)

Area scale ≫ 1 (inflated)

Greenland (test landmass)

Africa (test landmass)

Readout

Type

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Area

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Angles

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Greenland/Africa

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How it works

Every pixel is computed with the real forward-projection formula for lat/lon → x/y, not a decorative curve:

Mercator:        x=λ,  y=ln(tan(π/4+φ/2))
Mollweide:       2θ+sin2θ=π·sinφ (solved by Newton),
                 x=(2√2/π)·λ·cosθ,  y=√2·sinθ
Orthographic:    x=cosφ·sinΔλ
                 y=cosφ0·sinφ−sinφ0·cosφ·cosΔλ  (visible hemisphere only)
Stereographic:   k=2/(1+cosc),  x=k·cosφ·sinΔλ,  y=k·(…)

The colour on each 15°×15° graticule cell is the real local area-scale factor k·h = (∂x/∂λ·∂y/∂φ − ∂x/∂φ·∂y/∂λ) / cosφ, evaluated by finite differences of the actual projection function — this is the same quantity a Tissot indicatrix visualises, drawn here as a distortion heatmap over the whole map instead of at sample points. Mercator's factor grows as sec²φ (unbounded toward the poles); Mollweide, being a genuine equal-area projection, holds it at 1.0 everywhere. Two simplified test landmasses (Greenland, Africa) are projected the same way so you can see directly why Mercator makes Greenland look continent-sized next to Africa, even though Africa's true area is about 14× larger.