Χρήση συστημάτων πληροφορικής στην οδική υποδομή

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1 ΕΘΝΙΚΟ ΜΕΤΣΟΒΙΟ ΠΟΛΥΤΕΧΝΕΙΟ ΕΜΠ Εργαστήριο Συγκοινωνιακής Τεχνικής Χρήση συστημάτων πληροφορικής στην οδική υποδομή Χωρική Μοντελοποίηση Βύρωνας Νάκος Καθηγήτης ΕΜΠ

2 Άδεια χρήσης Το παρόν εκπαιδευτικό υλικό υπόκειται σε άδειες χρήσης Creative Commons. Για εκπαιδευτικό υλικό, όπως εικόνες, που υπόκειται σε άδεια χρήσης άλλου τύπου, αυτή πρέπει να αναφέρεται ρητώς. 2

3 Συστήματα Γεωγραφικών Πληροφοριών & Μεταφορές Χωρική μοντελοποίηση Βύρωνας Νάκος, Καθηγητής Ε.Μ.Π.

4 Contents Levels of data abstraction Why & how topology? Classes of spatial data models Spatial data structures Vector data structure Geo-relational model Object-oriented relational model Network model of GIS-T

5 321 Levels of data abstraction Polygons 4 Name Pointer Lines Lines 1 List Points 2 Nodes x y strings 1 Names X Y xy, xy, x y data structure real world data model 4 x y file structure 323 Name Points Length from to left right end of file marker end of chain marker (Peuquet 1984)

6 Why topology? Explicit representation of real world Efficient data input and storage Efficient data retrieval and query Construction of complex data object Detection of data error Data integrity maintenance

7 How topology? Topology is implemented as a set of integrity rules that define the behavior of spatially related geographic features and feature classes Topology rules, when applied to geographic features or feature classes in a geo-database, enable GIS users to model such spatial relationships For example: Containment (do parcel polygons overlap?) Connectivity (are all of road lines connected?) Adjacency (are there gaps between parcel polygons?) Topology is also used to manage the integrity of spatial databases (i.e., coincidence between different features)

8 Classes of spatial data models Field model Representation of the continuous variation of a phenomenon over space (terrain elevation) Discrete model Discrete entities - points, lines or polygons - populate space (highway rest areas, toll barriers, urbanized areas) Network model Topological representation of connected linear entities that are fixed in the continuous reference surface (roads, rail lines, or airlines) (Goodchild 1992)

9 Spatial data structures Vector A data structure that uses points, lines, or polygons to describe geographic space Raster A data structure that uses sets of regular tesselated units to describe geographic space

10 Spatial data structures Raster Vector

11 Vector data structure Point Points are defied by pairs of x & y co-ordinates Line (Arc) Lines are defined by sets of points linked together with line segments Polygons Polygons are spaces enclosed by lines (It is possible to have complex polygons with different variants, e.g. holes)

12 Geo-relational model Polygon Table Name Area Perimeter Line Table Name From To Left Poly Right poly Point 0 Table Name 0 x 3 y

13 Geo-relational model Designed to relate spatial to non-spatial data Both spatial and non-spatial data stored in relational tables Points, lines and polygons are stored in feature attribute tables Each entity is assigned a unique feature identifier Topological information is explicitly stored Non-spatial attribute data are stored in relational tables Entities in the spatial and non-spatial relational tables are linked by the common feature id s of entities

14 Object-oriented relational model The object-oriented relational model combines the concepts of objects and methods from the object-oriented model with the concept of relations from the entity-relationship model Integrates the traditional relational & an object-oriented data model The idea of object-oriented data model is to represent the reality with objects that people recognize easier Brings a physical model closer to its logical model The users work with objects of interests such as buildings, roads, & lakes

15 Network model of GIS-T The network model is based on mathematical graph theory and employs nodes & links Node A node can be a point where two lines are intersect, an end point of a line, or a given point on a line Link (edge) A link is a segment of a line between two nodes Links have a start node & an end node & therefore have a direction

16 An example of a GIS-T physical data model (Butler 2002)

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18 References Bernhardsen T., 2002, Geographic Information Systems. An Introduction (3rd ed.), New York: John Wiley & Sons. Burrough P.A. & McDonnell R., 1998, Principles of Geographical Information Systems, Oxford: Oxford University Press. Butler A., 2002, Transportation Networks in ArcGIS: An Alternative to Geometric Networks. ESRI International User Conference ( proc02 /pap0437/p0437.htm). Goodchild, M.F. (1992) Geographical data modeling, Computers and Geosciences, 18(4): Peuquet D.J., 1984, Conceptual framework and comparison of spatial data models, Cartographica, 24(1):

19 Χρηματοδότηση Το παρόν υλικό έχει αναπτυχθεί στα πλαίσια του εκπαιδευτικού έργου του διδάσκοντα. Το έργο υλοποιείται στο πλαίσιο του Επιχειρησιακού Προγράμματος «Εκπαίδευση και Δια Βίου Μάθηση» και συγχρηματοδοτείται από την Ευρωπαϊκή Ένωση (Ευρωπαϊκό Κοινωνικό Ταμείο) και από εθνικούς πόρους. 1