Gis Concepts 3/5

Concepts and Functions of Geographic Information Systems (3/5) MSc GIS - Alexander Mogollon Diaz Department of Agronomy 2009

Concepts and Functions of GIS .PPT Topic #1 Topic #2 Topic #3 1 A GIS is an information system GIS is a technology 2 Spatial Data modelling Sources of data for geodatasets Metadata 3 Geospatial referencing Coordinate transformations 4 Database management 5 Spatial Analysis

Functionalities of GIS INPUT QUERY - DISPLAY - MAP ANALYSE STRUCTURE MANAGE TRANSFORM

Transformations for building a spatial model / gDB ,[object Object],[object Object],[object Object],[object Object],[object Object]

Transformation of coordinates and Geospatial refence systems ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The Earth’s shape is irregular Positioning needs simplification ,[object Object],[object Object],[object Object],[object Object]

Geoid versus Ellipsoid ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Geospatial locations are expressed relative to an ellipsoid (1) ,[object Object],[object Object],[object Object],[object Object],[object Object]

Geospatial locations are expressed relative to an ellipsoid (2) LON LAT 45° N; 120°E

Geospatial locations are expressed relative to an ellipsoid (3) ,[object Object],[object Object],[object Object],[object Object]

Geospatial locations are expressed relative to an ellipsoid (4) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

From geographic coordinates to projected coordinates ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

From geographic coordinates to projected coordinates ,[object Object],[object Object],[object Object],[object Object],[object Object]

From geographic coordinates to projected coordinates ,[object Object],[object Object],[object Object]

Plane – cone - cylinder Tangent - secant Normal – transversal - oblique

Choice of the projection function ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Projection creates geometric distortion

Conformal projections Shape and/or direction is preserved Distances and areas are distorted

Mercator-projection = conformal

Transverse Mercator-projection = conformal

Universal Transverse Mercator projection ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Standard projected coordinate system for the Philippines ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Lambert conformal conical projection

Standard projected coordinate system for Belgium ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Other coordinate systems: examples

A gDB ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Transformation of coordinates for vertical/horizontal integration ,[object Object],[object Object],[object Object],[object Object]

Numeric coordinate transformation ,[object Object],[object Object],[object Object]

Geo-referencing ,[object Object],[object Object],[object Object]

Numeric transformation of coordinates after A/D-conversion via digitization ,[object Object],[object Object],[object Object],X Y (0,0) ,[object Object],(X i ,Y i )

Numeric transformation of digitizer- to gDB-coordinates ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

AFFINE transformation of digitizer- to gDB-coordinates

AFFINE-transformation & RMSe: X

AFFINE-transformation & RMSe: Y

AFFINE-transformation & RMSe: X & Y

Judgement of the RMSe ,[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],AFFINE = polynomial transformation of the 1st order

[object Object],[object Object],[object Object],Polynomial transformations of higher orders (rubber sheeting, warping)

Numeric transformation of coordinates after A/D-conversion via Scanning

Numeric transformation of scan- to gDB-coordinates ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Forward GCP-based transformation distorts the raster 1 2 3 Xo = f (Xi,Yi); Yo = f (Xi,Yi): NOT valid

Backward/Inverse polynomial transformation of scan- to gDB-coordinates ,[object Object],[object Object],[object Object],[object Object],[object Object]

Resampling ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Resampling is necessary after transformation of scan- into gDB-coordinates R = input raster; R’ = output raster Antrop & De Maeyer, 2005 Xi,Yi = Xo,Yo (change of resolution only) Xi,Yi <>Xo,Yo (nearest neighbour) Xi,Yi <> Xo,Yo (bilinear interpolation) Xi,Yi <> Xo,Yo (cubic convolution)

Numeric coordinate transformation ,[object Object],[object Object],[object Object],[object Object]

(Non-)systematic numeric coordinate-transformations ,[object Object],[object Object],[object Object]

Non-systematic transformations for further improvement of the positional quality of the georeferenced geodatasets ,[object Object],[object Object],[object Object],[object Object]

Non-systematic coordinate transformations ,[object Object],[object Object]

Rubber-sheeting 1 2 3 GCP1: X i1 ,Y i1 -> X o1 ,Y o1 GCP2: X i2 ,Y i2 -> X o2 ,Y o2 GCP3: X i3 ,Y i3 -> X o3 ,Y o3 GCPA...GCPF: X i = X o ; Y i = Y o A B D E F G C

Rubber-sheeting ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Edge-matching ,[object Object],[object Object],[object Object],[object Object]

Summary of important items ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Questions or remarks ? Thank you …

Gis Concepts 3/5

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