1. Introduction to Geoinformatics L-3. Georeferencing
Dr. György SZABÓ associate professor
Budapest University of Technology and Economy
Department of Photogrammetry and Geoinformatics

2. Contents
OVERVIEW
Discuss the necessity of commonly used systems, including place names and street addresses, 2D, 3D coordinates, linear referencing, GSM, conversion between different georeferencing systems
LEARNING OBJECTIVES
Know the requirements for an effective system of georeferencing;
Be familiar with the problems associated with placenames, street addresses, and other systems used every day by humans;
Know how the Earth is measured and modeled for the purposes of positioning;
Know the basic principles of map projections, and the details of some commonly used projections;
Know about conversion between different systems of georeferencing
Longley, Goodchild, Maguire, Rhind (2011): Geographical Information Systems and Science
CH – 5. pp

3. How can we manage the complexity of our environment?

4. Georefrences and Coordinate Systems
Necessity of common system
Contionous georeferencing
Relative georeferencing
Polar coordinates, Offset, Linear ref.
Direct georeferencing
Datums
Map projections
Coordinate systems
Elevation referencing
Discrete georeferencing
Adresses, postal codes, Grids, Zones, GSM Cell

5. Importance of Georeference
Dissimilar geographic data in one GIS project
Different conceptual, logical, geometrical representation
Traditionally different description of real world
->Necessity of common system

6. Properties of the Reference Systems
Precision
Surveying: no angular and area, limited linear distorsion 1/10000, sub-dm accuracy
Topography: limited angular, area and linear distorsion ~ m accuracy
Geography/bussiness: importance of visualisation not accuracy
Dimensions
1D : elevation reference, local vetical observations
2D : planar and sphere/ellipsoidal surface observations
3D : real 3d geocentral observations
Principal methods
Continouos (Direct, Relative) georeferencing / to access every point in the reference system
Discrete georeferencing / to access discrete zone with limited positional accuracy

7. Discrete georeferencing
Position of phenomena are measured relative to a fix, limited surface of the Earth:
Adresses, street codes
Cadastral parcel ID
Postal codes, Geographic names
Administrativ zones, statistical units
Grids, Map sheets (quad-tree)
GSM Cell, WIFI Zone, IP address
Geocoding: connection between the Direct and Discrete systems

8. General city postal address situation

9. International examples
Your home country?

10. Hungary / BME Library 1111 Budapest Műegyetem rkp.3. Hungary
Budapest Bertalan Lajos u H-1111, Hungary
1111 Budapest Budafoki u Magyarország

11. Relationships between UPU postal address components

12. Rural situation (no street names)

13. Discrete georeferencing samples
DIGI TV coverage zones
Bank Office zones and account distribution

14. The location of a GSM user – LBS services

15. Contionous georeferencing
-> Continous measurement of position of phenomena in relation to a refference point
Relative (indirect) georeferencing:
Polar coordinates
Offset distance
Linear measurement along networks (road, river)
Direct georeferencing of points, lines, areas:
Coordinates on the curved surface of the Earth (2D)
Geocentric coordinates (3D)
Rectangular coordinates (2D)
Vertical coordinates, elevations (1D)

16. Relative (indirect) georeferencing
Practical on-site referencing
Polar coordinates
Offset distance
Linear measurement along networks (road, river)

17. Direct Georeferencing
Components: Datum, Map projection, Coordinate system
Datum: modell, reference level of the Earth used for geodetic calculations
Map projection: projected the curved surface of the Earth to plane surface
Coordinate system: a reference systems to serve the geometrical computations

18. Datum – Earth modells Plan Sphere Geoid Ellipsoid II. century Bc.
XVII. century Ac.
XIX. century Ac.
Plan
Sphere
Geoid
Ellipsoid

19. Ellipsoid Definitions
Name
Year
Half big-axis (m)
Flatness
=(a-b)/a
Walbeck
1819
1/302.78
Bessel
1837 1/
Hayford
1924
1/297
Kraszovszkij
1940
1/298.3
IUGG 67
1967 1/
WGS 84
1984 1/
ETRS
1989 1/

20. Coordinate Systems Geocentral P(x,y,z) Ellipsoidal P(lat, long) Plan
X = f1(Ф,Λ)
Y = f2(Ф,Λ) Y N N X
Geocentral
P(x,y,z)
Ellipsoidal
P(lat, long)
Plan
P(x, y)

21. The basis for three types of map projections—cylindrical, planar/azimutal, and conic.
In each case a sheet of paper is wrapped around the Earth, and positions of objects on the Earth’s surface are projected onto the paper. The cylindrical projection is shown in the tangent case, with the paper touching the surface, but the planar and conic projections are shown in the secant case, where the paper cuts into the surface.
(Reproduced by permission of Peter H. Dana)

22. Examples of some common map projections
Examples of some common map projections. The Mercator projection is a tangent cylindrical type, shown here in its familiar equatorial aspect (cylinder wrapped around the equator).
The Lambert Conformal Conic projection is a secant conic type. In this instance, the cone onto which the surface was projected intersected the Earth along two lines of latitude: 20 North and 60 North.
(Reproduced by permission of Peter H. Dana)

23. (A) The so-called unprojected or Plate Carrée projection, a tangent cylindrical projection formed by using longitude as x and latitude as y.
(B) A comparison of three familiar projections of the United States. The Lambert Conformal Conic is the one most often encountered when the United States is projected alone and is the only one of the three to curve the parallels of latitude, including the northern border on the 49th Parallel.
(Reproduced by permission of Peter H. Dana)

24. The UTM (Universal Transver Mercator) projection

25. The system of zones of the Universal Transverse Mercator system
The system of zones of the Universal Transverse Mercator system. The zones are identified at the top. Each zone is six degrees of longitude in width
(Reproduced by permission of Peter H. Dana)

27. Major features of UTM Zone 14 (from 102 W to 96 W)
Major features of UTM Zone 14 (from 102 W to 96 W). The central meridian is at 99 W. Scale factors vary from at the central meridian to at the zone boundaries. See text for details of the coordinate system.
(Reproduced by permission of Peter H. Dana)

28. Elevation referencing
Geoid: mean see level, at the same level of the gravitational potential
GPS -> P(x,y, ellipsoid height) !!!
Earth surface
H: geoid height
h: ellipsoid height
n: Geoid undulation
h=H-n
Geoid
Ellipsoid

29. Direct reference system: Map Discrete reference: adresses
Geocoding/Geotagging
Direct reference system: Map
Bussiness Analysis
Geocoding
Discrete reference: adresses

30. Georegistration: transformation between Planimetric Systems
Helmert – 4 parameter:
x = a0 + a1 x’ – a2 y’
y = b0 + a1 y’ + a2 x’
Affin – 6 parameter:
x = a0 + a1 x’ + a2 y’
y = b0 + b1 x’ + b2 y’.

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