# GIS data models

```Prepared by Abzamiyeva Laura
Candidate of the department of KKGU
named after Al-Farabi
Kizilorda, Kazakstan 2012
Object
• Introduction of GIS
• Data modeling
What is GIS ?
“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)
GIS Functional Modules
Data Input
Database
Query and
Analysis
Output and
Visualization
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).
→ https://www.e-education.psu.edu/natureofgeoinfo/book/export/html/1604
Characteristics of Geographic Data
 Spatial data:
features orientation shape, size
&amp; structure
 Non-Spatial data: Information about various
attributes like area, length &amp;
population
Characteristics of Spatial Data
 spatial reference
 where?
 attributes
 what?
 spatial relationships
 how?
 temporal component
 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 structure
•Abstracts 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 &amp; attribute information within a GIS
• A composite model (raster)
• Geo-relational model (vector)
Implementation Models
Field View
 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
10100100111
Visualization
Representation
Generalization
Storage
Maps
 Best known conventional model
 Two-dimensional
 Static
 Visualization as their major function
 Small-scale = less detail, larger area
(e.g. 1:1.000.000)
 Large-scale = more detail, smaller area (e.g.
1:10.000)
 Generalization (scale-dependant)
Databases
 Store representations of spatial
phenomena in the real world
 Data models are languages used to
define a database
 The complete database definition is
the database schema
 Spatial databases are scaleless and
seamless
spatial data models
 two fundamental approaches:
raster model
 vector model

a raster view of the world...
Features
Raster
Tessellation
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:
 Points
 Lines
 Areas
X,Y coordinate pair + label
series of points
line(s) forming their boundary
(series of polygons)
line
feature
point
feature
area
feature
vector model
vector model
layers in a raster model
Layer 1
Layer 2
Reference:
→ http://www→MapServer
→OpenLayers
THANK YOU !
```