Gnomonic Projection Lab

Move countries across the map, switch on distortion layers, and see what the Gnomonic projection changes.

Select map projection:

Projection center25.0°, 0.0°

The center defines the visible part of the hemisphere. Great circles remain straight.

Add country to compare:

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Quick start

Add a country, then drag its outline anywhere on the map.

Map appearance

Change the background and contrast of every layer.

Map layersProjection diagnostics

Tissot's indicatrices

Equal-sized circles on the globe. Their distortion on the map instantly reveals how the projection alters area and shape.

Area isocolesA

Lines joining places with the same relative area inflation. They work like contour lines on a topographic map of error.

Angular isocolesω

Lines of equal maximum angular deformation. On conformal projections such as Mercator, this layer remains empty.

True-north field↑N

Arrows show where geographic north lies on the screen. Their rotation reveals how a projection alters directions.

Geographic context

Equator, tropics & polar circles

Five major parallels anchor Earth's zones and reveal how the projection stretches high latitudes.

Ocean currents

An animated, simplified view of major surface currents — especially revealing on ocean-centred projections.

Day & night

Draws the day/night boundary (terminator) — a great circle that every projection bends differently. Drag the slider to change the time.

Antipodes

Overlays each selected country's outline at its antipode (the opposite side of the globe). Unavailable on the globe view.

Atlas of error · liveGnomonicClick or tap a country to add its outline