LINZS25002 Standard for New Zealand Geodetic Datum 2000 Projections Version 2
Datum and Projections.
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Datum and Projections
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Overview Coordinate Systems Datum Map Projections Map Scale Cartesian Geographic Datum Local Global Map Projections Types & Differences Map Scale Large & small
Transcript of Datum and Projections.
Datum and Projections
Overview Coordinate Systems
Cartesian Geographic
Datum Local Global
Map Projections Types & Differences
Map Scale Large & small
Coordinate SystemsA method of representing points in a space of given dimensions by coordinates
Coordinate Systems – Cartesian
- X, + Y + X, + Y
- X, - Y + X, - Y
X
Y
40, 50
Cartesian coordinate system
Measures of length and angle are uniform
Coordinate Systems – geographic
Measures of length and angle are not uniform
DatumA frame of reference for measuring locations on the
surface of the Earth
Different datum locates the same point in different places
Datum DifferencesA different datum locates the same point in a different place
Ohene Djan Stadium
WGS84
OSGB36
Map ProjectionsMap projections convert curved surfaces to flat surfaces
Map Projections – Comparison
Mercator Robinson
Map Projections – Various Others
Map Projections – DistortionsDistortions make geographers S.A.D.D.
Shape
Area
Distance
Direction
Map Projections – TypesGenerally classified by the spatial attribute they preserve
Projection Preserves ExampleConformal Angles Mercator
Equal-Area Area Gall-Peters
Equidistant Distance Plate carrée
Compromise “Look” Robinson
Map Projections – Storing InformationMany spatial data store the projection details with the data
Map Scale Map scale determines the size and shape of features
1:500
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
