1 Coordinate Systems exercise session WiSe 2020/2021 Map Projections Sven Gedicke Institute of Geodesy and Geoinformation University of Bonn
2 - 1 Motivation map projection point on reference surface (e.g. sphere, ellipsoid) is mapped to plane
2 - 2 Motivation map projection point on reference surface (e.g. sphere, ellipsoid) is mapped to plane → different map projections cause different distortions
3 - 1 Motivation mercator projection map areas between lines of constant latitude/longitude to rectangles that preserve aspect ratios. b = a ′ a b ′ b ′ b a a ′
3 - 2 Motivation mercator projection map areas between lines of constant latitude/longitude to rectangles that preserve aspect ratios. → angles are preserved b = a ′ a → areas are distorted b ′ b ′ (esp. close to poles) b a a ′
4 - 1 Motivation cylindrical equal-area projection map areas between lines of constant latitude/longitude to rectangles of the same sizes. ab = a ′ b ′ b ′ b a ′ a
4 - 2 Motivation cylindrical equal-area projection map areas between lines of constant latitude/longitude to rectangles of the same sizes. → distorted aspect ratios → distorted angles ab = a ′ b ′ b ′ b a ′ a
5 Exercise mercator projection cylindrical equal-area projection vs . thetruesize.com
6 Tutorial QGIS QGIS is a free desktop geographic information system (GIS) application for (23. September 2020) • viewing • editing • analyzing geospatial data. Download: https://www.qgis.org/de/site/
7 Any questions? Sven Gedicke → gedicke[at]igg.uni-bonn.de
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