Chapter 9. Geographic Representation Models. Emmanuel Stefanakis

Transcription

1 Stefanakis, E., Geographic Databases and Information Systems. CreateSpace Independent Publ. [In English], pp.386. Get a copy from Amazon Chapter 9 Geographic Representation Models Emmanuel Stefanakis

2 Models Representation of Reality Representation model Data model Reality Image of Reality (human perception) Representation on a Computer (implementation) 2

3 Objectives should answer two questions what is present? where is it located? What? Where? 3

4 Models two approaches space as a set of discrete entities space as a continuous field What? Where???? 4

5 Model 1 space as a set of discrete entities entities should be identifiable relevant to the application with sharp boundaries describable (with attributes) 5

6 Model 1 space as a set of discrete entities in 2D static space entities are represented by» points» lines» polygons based on an orthogonal or map projection in a 2D plane surface 6

7 Model 2 space as a continuous field each location of the field is assigned one value for an attribute of interest» elevation» vegetation» temperature» humidity??? 7

8 Model 2 space as a continuous field fields are characterized by what is changing» e.g., elevation how smoothly it changes» e.g., steep slope 8

9 Thematic layers space is split into sub-spaces each sub-space corresponds to a theme (thematic dimension) 9

10 Tomlin s Model geographic data forms a hierarchy map thematic layer 1 thematic layer 2 thematic layer 3 zone 1 zone 2 zone 3 location 1 location 2 location 3 10

11 Tomlin s Model can represent both discrete entities and continuous fields... map thematic layer 1 thematic layer 2 thematic layer 3 Continuous fields zone 1 zone 2 zone 3 Discrete entities location 1 location 2 location 3 11

12 1 h 10 min 1 h 00 min 0 h 50 min 0 h 40 min Tomlin s Model In a dynamic world map 0 h 30 min 0 h 20 min 0 h 10 min 0 h 00 min Sailing in the Aegean Sea Κέα Κύθνος Γυάρος Σύρος Άνδρος Τήνος Ρήνεια Δήλος Μύκονος thematic layer 1 thematic layer 2 thematic layer 3 Space-time cubes (2+1D modeling space) zone 1 zone 2 zone 3 location 1 location 2 location 3 Space-time locations 12

13 Tomlin s Model In a dynamic world individual location T Dec. 22, :59 Y Dec. 22, :00 X 13

14 Tomlin s Model In a fuzzy dynamic world Map GREECE Thematic Layer 1 Thematic Layer 2 Thematic Layer k T 2000 Crete individual location dry-land: 0.2 Lexical Layer 1 Lexical Layer 2 Lexical Layer j Zone 1 Zone 2 Zone i 1901 Y X vineyard: 0 orchard: 0 location 1 location 2 location n vegetation layer forest:

15 We should be able to represent Spatial Entities + Spatial Relations Entities? Relations? B N E C F Y Company ltd X A D G 15

16 Spatial relations they come from the relative positions of geographic entities in space most common topological relations neighbor, overlap, etc. order relations (direction relations) in_front_of, north_of, etc. metric relations (distance relations) near, far, etc. 16

17 Topological relations topology studies the geometric relations of objects that are preserved under any translation, rotation or (topological transformations) scale change 17

18 Topological relations 18

19 Topological relations a model for representing them for two entities A, B B A, B B the border lines I A, I B the interior areas check the four intersections B A B B I A I B I A B B B A I B 19

20 Topological relations (Egenhofer s relations) 20

21 Topological relations A 3x3 (or 9) intersection matrix specifies the topological relationship e.g., A TOUCH B A B B b i e b A i e

22 Temporal relations (Allen s relations) Temporal relation Definition Α before Β A t B Α equal to Β A B Α meets Β t A t B Α during Β A B Α overlaps Β t A B t Α ends Β B A Α starts Β A B t t 22

23 Stefanakis, E., Geographic Databases and Information Systems. CreateSpace Independent Publ. [In English], pp.386. Get a copy from Amazon Chapter 9 Geographic Representation Models Emmanuel Stefanakis