SVY2001: Databases for GIS Lecture 15: Introduction to GIS and Attribute Data Management. Dr Stuart Barr School of Civil Engineering & Geosciences University of Newcastle upon Tyne. Email: S.L.Barr@ncl.ac.uk Lecture 3: Relational database normalisation 1
Lecture Objectives & Contents Objectives: To Cover the traditional approach to modelling spatial and attribute data within Geographical Information Systems. Contents: t GIS, data & analysis. Representing the spatial component. Attribute representation. Typical GIS operations and attribute implications. Lecture 3: Relational database normalisation 2
Geographical Data Burrough & McDonnell (1998)... all geographical phenomenon can, in 2 dimensions at least, be represented by three basic entity types : P(X,Y) P1(X,Y) P2(X,Y) P1(X,Y) P2(X,Y) P5(X,Y) P4(X,Y) P3(X,Y) Lecture 3: Relational database normalisation 3
Geographical Data Each type of geographical data has several components: A Location component - a description of where it is and its geometric/geographical extent. An attribute component - non-spatial information describing the geographical entity. Lecture 3: Relational database normalisation 4
Organising Space in the GIS The most popular approach is to divide space into thematic layers which form the fundamental basis of analysis. A further important concept of GIS layers is Tiling: Spatial composting of geographically g coincident layers. Assists in storage and handling of very large data-sets. Lecture 3: Relational database normalisation 5
The Two Spatial Data Models Vector Raster Lecture 3: Relational database normalisation 6
Vector Data Structures Vector data structures fall in to one of two different types depending on whether they do or do not represent/encode The geometric relationships that exist between entities located in space. It can be thought of as the study of how entities are organised relative to one another - whether they are connected, adjacent or contained. Topological relations are invariant to stretching, bending, rotation and scaling. Lecture 3: Relational database normalisation 7
Vector Topological Arc-Node Lecture 3: Relational database normalisation 8
Vector Topological Polygon-Arc Poly Arc 1 1, 3, 4 2 2, 3, 5 Arc Coordinates 1 (1,8), (1,3) 2 (1,3), (3,4) Lecture 3: Relational database normalisation 9
Vector Data Structures -Topological og In many GIS packages vector topology has to be explicitly built (e.g., ArcGIS Build command). If it is not then we have a simple spaghetti structure. Below is an arc attribute t table no topology is present, hence we do not know which Nodes form Arcs. Lecture 3: Relational database normalisation 10
Vector Data Structures - Topological The coverage after Arc topology has been built in ArcGIS. Look at what we now know about the geometric connectivity. Lecture 3: Relational database normalisation 11
Vector & Attribute Storage Traditionally vector topology and attribute information stored in separate files. E.g., ARC/INFO coverages (predecessor to ArcGIS): ARC vector topology. INFO partial relational data structure. ARC - Geometry INFO - Attribute Points PNT Lines AAT Polygons PAT Lecture 3: Relational database normalisation 12
Vector & Attribute Storage It is possible to view and manage geometry and attribute simultaneously BUT in most GIS stored separately. Lecture 3: Relational database normalisation 13
Vector & Attribute Operations - JOIN Join Label NEWPOP 2 230 Lecture 3: Relational database normalisation 14
Vector & Attribute Operations: RELATE Relate Label POP 2 230 Lecture 3: Relational database normalisation 15
The Overlay Operation - Union Lecture 3: Relational database normalisation 16
The Overlay Operation - Union Lecture 3: Relational database normalisation 17
The Overlay Operation & Attributes: Union The overlay operation changes not only the visible spatial pattern BUT also the attributes. They are joined and in some cases duplicated. Lecture 3: Relational database normalisation 18
The Overlay Operation - Intersection Lecture 3: Relational database normalisation 19
The Overlay Operation & Attributes: Intersection The overlay operation changes not only the visible spatial pattern BUT also the attributes. They are joined and in some cases duplicated. d Lecture 3: Relational database normalisation 20
Attribute Operations - Selection Lecture 3: Relational database normalisation 21
Attribute Operations Selection by Location All Census output areas that fall completely within an urban area. Lecture 3: Relational database normalisation 22
A Once in a Lifetime Offer! If today s material is new consider checking out the online SVY20004 material and possibly doing a couple of the ArcGIS practicals. Url: http://www.staff.ncl.ac.uk/s.l.barr/svy2004/svy2004.html Username: SVY2004_students Password: intersection Lecture 3: Relational database normalisation 23
Reading Lecture 15 Burrough & McDonnell - Principals of Geographical Information Systems. Pages 35-74. Longley, P.A., Goodchild, M.J., Maguire, D.J., and Rhind, D.W., 2001. Geographic Information Systems and Science. Pages 184-203. Worboys, M.F., and Duckham, M., 2004. GIS: A Computing Perspective. Pages 177-184 184 & 221-258 258 (Note: written very much from a computer science perspective). Franklin, W.M.R., 1991. Computer Systems and Low-Level Data Structures for GIS. In, Maguire, D.J., Goodchild, M.F., and Rhind, D.W., (eds), Geographical Information Systems: Principles i and Applications. pp 215-225. 225 Egenhofer, M.J., and Herring, J.R., 1991. High-Level Spatial data Structures for GIS. In, Maguire, D.J., Goodchild, M.F., and Rhind, D.W., (eds), Geographical Information Systems: Principles and Applications. pp 2001-237 237. Piquet, D.J., 1984. A Conceptual Framework and Comparison of Spatial Data Models. Cartographica, 21(4), pp 66-113. Healey, R.G., 1991. Database Management Systems. In, Maguire, D.J., Goodchild, M.F., and Rhind, D.W., (eds), Geographical Information Systems: Principles and Applications. pp 251-267. Jacobson, C.R., 1997. Non-spatial Database Models, NCGIA http://www.ncgia.ucsb.edu/giscc/units/u045/u045_f.html. Lecture 3: Relational database normalisation 24
SVY2001 L15: Introduction to GIS & Attribute Data Management Today we have: Reviewed the main spatial data structures used in GIS. Considered how attribute data is managed. Looked at the most common GIS operations. Next lecture: From Geo-relational to Arc SDE. Lecture 3: Relational database normalisation 25