Prepared by Abzamiyeva Laura Candidate of the department of KKGU named after Al-Farabi Kizilorda, Kazakstan 2012

Object Introduction of GIS Data modeling

“GIS is a computer-based system that provides the following four sets of capabilities to handle geo-referenced data: 1. Input 2. Data management (storage and retrieval) 3. Manipulation and analysis 4. Output.” (Aronoff, 1989) What is GIS ?

GIS Functional Modules Database Query and Analysis Output and Visualization Data Input

→ What does GIS? GIS deals with objects, their attributes, and the relationships among the objects. The objects are stored in a database using geometric primitives (volumes, areas, lines, points), their attributes and the relationships between them (topology).

Characteristics of Geographic Data l Spatial data: features orientation shape, size & structure l Non-Spatial data: Information about various attributes like area, length & population

l spatial reference l attributes l spatial relationships l temporal component Characteristics of Spatial Data where? what? how? when?

Data Model Data model represents the linkages between the real world domain of geographic data and the computer or GIS representation of these features. It helps (Marble, 1982) To organize a systematic file structureTo organize a systematic file structure Abstracts the real world into properties which are perceived by a specific applicationAbstracts the real world into properties which are perceived by a specific application

How to represent the really data? ?

GIS structures as representations of reality Two approaches have been widely adopted for representing the spatial & attribute information within a GIS A composite model (raster) A composite model (raster) Geo-relational model (vector) Geo-relational model (vector)

Implementation Models Field View l tessellation (raster, grid) – simple data structure – difficult to represent topology – suitable for image processing functions Object View vector (topological vector model) efficient representation of topology complex data structure certain functions are difficult to implement

Real (and Virtual) World Models Maps Databases Visualization Representation Generalization Storage

Best known conventional model Two-dimensional Static Visualization as their major function Small-scale = less detail, larger area (e.g. 1: ) Large-scale = more detail, smaller area (e.g. 1:10.000) Generalization (scale-dependant) Maps

Databases l Store representations of spatial phenomena in the real world l Data models are languages used to define a database l The complete database definition is the database schema l Spatial databases are scaleless and seamless

spatial data models l two fundamental approaches: l raster model l vector model

a raster view of the world... Tessellation Raster Features Sampling

raster model The entity information is explicitly recorded for a basic data unit (cell, grid or pixel)

vector model In a vector-based GIS data are handled as: PointsX,Y coordinate pair + label Linesseries of points Areasline(s) forming their boundary (series of polygons) line feature area feature point feature

vector model

layers in a raster model Layer 1 Layer 2

Reference: → → MapServer MapServer → OpenLayers OpenLayers

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