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Datum and Projections

This article provides an overview of coordinate systems, datum, and map projections, including their types, differences, and distortions. It explains how these concepts are used to represent points and surfaces on the Earth's surface in 2D. Relevant topics include Cartesian and geographic coordinate systems, various map projections, and the importance of map scale.

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Datum and Projections

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  1. Datum and Projections

  2. Overview • Coordinate Systems • Cartesian • Geographic • Datum • Local • Global • Map Projections • Types & Differences • Map Scale • Large & small

  3. Coordinate Systems A method of representing points in a space of given dimensions by coordinates

  4. Y 40, 50 • X, + Y + X, + Y X • X, - Y + X, - Y Coordinate Systems – Cartesian Measures of length and angle are uniform Cartesian coordinate system

  5. Coordinate Systems – geographic Measures of length and angle are not uniform Latitude longitude

  6. Datum A frame of reference for measuring locations on the surface of the Earth • Different datum locates the same point in different places

  7. Ohene Djan Stadium OSGB36 WGS84 Datum Differences A different datum locates the same point in a different place

  8. Map Projections Map projections convert curved surfaces to flat surfaces

  9. Map Projections – Comparison Mercator Robinson

  10. Map Projections – Various Others

  11. Shape Area Distance Direction Map Projections – Distortions Distortions make geographers S.A.D.D.

  12. Map Projections – Types Generally classified by the spatial attribute they preserve

  13. Map Projections – Storing Information Many spatial data store the projection details with the data

  14. Map Scale • Map scale determines the size and shape of features 1:500

  15. Summary • A coordinate system is a way to reference a location • A datum is way to model the shape of the Earth • A map projection is way represent the 3 dimensional surface of the Earth in 2 dimensions

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