Datums coordinate systems and map projections 3 Map

Datums, coordinate systems and map projections 3. Map distortions Lennert Schepers lennert. schepers@vliz. be Britt Lonneville britt. lonneville@vliz. be

Map distortions • Try to arrange an orange peel flat on a table • Every (flat) map has a distortion – Except: where projection plane is tangent/intersects ellipsoid • Properties of a map: – Conformal: shape – Equal area: area – Equidistant: distances → never all 3 together! → also possible that a map is none of them • Visualize with Tissot’s indicatrix

Map distortions - Mercator projection • Conformal (circle=circle) • Equal area • Equidistant (only along same latitude) • Application: – Navigation: constant course Maps by Tobias Jung (cc by-sa) map-projections. net

Map distortions - Gall-Peters projection • Conformal (circle=circle) • Equal area • Equidistant (only along same latitude) • Application: – Political school maps Maps by Tobias Jung (cc by-sa) map-projections. net

Map distortions – Lambert Conformal Conic • Conformal (circle=circle) • Equal area • Equidistant (only along same latitude) • Application: – State/regional maps • Europe • Belgium • . . . Maps by Tobias Jung (cc by-sa) map-projections. net

Map distortions – Azimuthal Equidistant Azimuthal equidistant projection • Conformal (circle=circle) • Equal area • Equidistant • Application: – Polar maps – Star maps – Radio/radar maps Maps by Tobias Jung (cc by-sa) map-projections. net

Compromises • Compromise world maps • Local projections: – Smaller areas = smaller distortions • Choose projection by purpose! Maps by Tobias Jung (cc by-sa) map-projections. net

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