GIS

1. The GIS Database
Chapter 7,8 & 9
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2. The backbone of GIS is good data accurate enough to
accomplish its objectives.
Geographic data are organized in a geographic database.
There aretwo important components
of this geographic database:
 geographic position (spatial data)-where is it?
 attributes or properties (attribute data)-
what things are?
GIS data types of are grouped into three classes:
i. Spatial data (where?): used to describe location, shape, size, and
all kinds features of spatial entities.
GIS Data Concepts

3. ii. Non-spatial data (what, when, in what amount?):
 also called attribute or characteristic data,
 Also known as descriptive data
 There are fundamental differences between them:
 spatial data are generally multi-
dimensionaland autocorrelated.
 are positional data
iii. Metadata: is data about data and contains information
about scale, accuracy, projection/datum, data source,
manipulations, how to acquire data.
GIS Data Concepts (Contd..,)

4. Digital Representation of Data
We need to come up with a digital representations of the geographic
phenomena in order to store them in a GIS.

5. Regular Tessellation
Examples of raster data representation are
aerial photograph, a satellite image, or a scanned
map, etc.
 In raster representation the field attribute value assigned
to a cell is associated with the entire area occupied by the
cell.
 The size of the area that a single raster cell represents is
called the raster’s resolution.
Reality
Raster Representation (Contd..,)

6. Vector representations useful for representing and
storing discrete features such as buildings, pipes, or
parcel boundaries and can be:
 Triangulated Irregular Networks (TIN)
 Point
 Line
 Area
i. TIN
 A TIN is built from a set of
measurements for example points of height.
 These points can be scattered unevenly
over the study area, with areas of more change
having more points.
 Triangles are fitted through three points to form planes.
Vector Representations

7.  ATin is a vector representation
• Each anchor point has a stored geo-reference.
• The planes do not have a stored values (like raster cells have)
No value is stored
for this plane
Ageo-reference and value is
stored for each anchor point
Stretched
triangles
Delaunay
triangulation
Elevation for TIN
construction
Vector Representations (Contd..,)

8. ii. Point
Points are defined as:
• single coordinate pairs (x,y) when we work in 2D;
• coordinate triplets (x,y,z) when we work in 3D.
Mekelle City can be represented both in point and polygon. HOW??
 Used to represent shape and size less single features such as:
tree, oil well, poles, fire plugs, etc.
iii. Line
 Used to represent one dimensional objects
(roads, railroads, canals, rivers, etc.)
Line is defined b des to define
the shape of the l
y 2 end nodes and 0-n internal no
ine.
Vector Representations (Contd..,)

9. iv.Area (polygon)
 Used to represent two dimensional features.
 Polygonal features, such as city boundaries and river
catchments can be stored as a closed loop of
coordinates.
 Polygonal data is the most common type of data in
natural resource applications.
 Examples of polygonal data include forest stands, soil
classification areas, administrative boundaries, and
climate zones.
Vector Representations (Contd..,)

10. Raster Model Vector Model
Advantages:
Simple data structure
Easy and efficient overlaying
Compatible with RS imagery
High spatial variability is efficiently
represented
Simple for own programming
Disadvantages:
Need high computer storage
Errors in perimeter and shape
Difficult network analysis
Inefficient in projection transformations
Loss of information when using large
cells
Advantages:
Compact data structure
Efficient for network analysis
Efficient for projection
transformation
Accurate map output.
Disadvantages:
Complex data structure
Difficult overlay operations
High spatial variability is
inefficiently represented
Not compatible with RS imagery
Raster vs Vector (Contd..,)

11. What is a database?
A database is any organized collection of
data. Some examples common examples:
– a telephone book
– T.V. Guide
– airline reservation system
– motor vehicle registration records
– papers in your filing cabinet
– files on your computer hard drive.
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12.  A database can be defined as:
 A collection of related data/information stored in a structured
format.
 Computerized collection of structured data stored in one or
more tables as electronic filing cabinet.
 A collection of inter-related data stored together to serve one or
more applications.
 A combination of software and hardware that makes it possible
and convenient to perform tasks that involve handling large
amounts of data.
 The data are stored together with as little redundancy as
possible to serve one or more users.
Database

13. Database Definitions
What is a database?
It’s an organized collection of data, it need not be a computer
based system.
What is a database management system
(DBMS)?
A software system designed to:
– Organize that data in a flexible manner,
– Provide tools to add, modify or delete data from the database,
– Query the data,
– Produce reports summarizing selected contents.
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14. What is the ultimate purpose of
a database management
system?
Data Information Knowledge Action
Is to transform
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15. Features of a DBMS
Database Management Systems provide features
to maintain database:
– Transaction management - A transaction comprises
a unit of work performed within a DBMS against a
database, and treated in a coherent and reliable way
independent of other transactions. Transactions in a
database environment have two main purposes:
• To provide isolation from other transactions.
• To have an “all or nothing” effect.
Transactions must pass the ACID test (atomic, consistent,
isolated and durable
Lecture 8 15

16. Features of a DBMS
Database Management Systems provide features
to maintain database:
– Concurrency control - ensures that correct results for
concurrent operations are generated, while getting
those results as quickly as possible.
– Backup and recovery
– Provides a language for the creation and querying of
the database.
– A language for writing application programs
Lecture 8 16

17. Features of a DBMS
Database Management Systems provide features
to maintain database:
– Data independence - It refers to the immunity of user
applications to make changes in the definition and
organization of data.
– Integrity and security - refers to maintaining and
assuring the accuracy and consistency of data over
its entire life-cycle
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18. DATA BASE MANAGEMENT SYSTEM:
❖Dale and McLaughlin (1988) define a DBMS as a
computer program to control the storage, retrieval
and modification of data (in a database)
❖Stern and Stern (1993), a DBMS will allow users to
joint, manipulate or otherwise access the data in
any number of database files.

19.  Spatial database is a collection of spatially referenced
data that acts as a model of reality.
 To create and maintain a computer database, you need
a database program, often called:
 Database Management System (DBMS).
 DBMS is a software package that allows the user to set
up, create and maintain a database.
 GIS is a DBMS specifically designed for processing of
spatial and related attribute data.
In addition to DBMS, GIS also has many capabilities.
A geographic database is a critical part of GIS.
Database Management Systems (Contd..,)

20.  Handling large amounts of data.
 Backup and recovery functions to avoid loss of data.
 Declarative query language for retrieval of data.
 Collecting all data at a single location reduces
duplication.
redundancy and
 Maintenance costs decrease because of better organization and decreased
data duplication.
 Applications become data independent so that multiple applications can
use the same data.
 User knowledge can be transferred between
applications more easily because the database remains constant.
 Data sharing is facilitated and a corporate view of data can be provided
to all managers and users.
 Security and standards for data and data access can be established and
enforced.
Why Use a Database?

21. Selecting a Database
Management System
Database management systems (or DBMSs)
can be divided into two categories:
– Desktop databases are oriented toward single-user
applications and reside on standard personal
computers (hence the term desktop).
– Server databases contain mechanisms to ensure the
reliability and consistency of data and are geared
toward multi-user applications.
Lecture 8 21

22. Relational Databases
• The relational database model is the most
dominant model in both the corporate and GIS
world, due to its flexibility, organization, and
functioning..
• It was defined by Edgar F. Codd (1970).
• It can accommodate a wide range of data types.
• It is not necessary to know beforehand the types
of processing that will be performed on the
database.
Lecture 8 22

23. Relational DBMS is most widely accepted for managing
the attributes of geographic data.
The relational DBMS is attractive because of its:
 Simplicity in organization and data modeling.
 Flexibility - data can be manipulated in an ad hoc manner by
joining tables.
 Efficiency of storage- by the proper
design of data tables
redundant data can be minimized; and
 The non-procedural nature - queries on a relational database do
not need to take into account the internal organization of the
data.
Disadvantages
 No explicit representation of relationships.
 Reduced performance for large, well-defined databases.
Relational DBMS

24.  Define database structure: attribute, tuples and relations.
 Define integrity rules.
 Define queries (extract without alteration).
 Transactions (change database contents).
 Comprises a set of tables, each a two-D list of records.
containing attributes about the objects under study.
 Were primarily focused on business applications such as
banking, human resource management.
 Were never designed to deal with rich data types such as
geographic objects, sound, and video.
 Poor performance for many types of geographic query.
Relational DBMS (Contd..,)

25. Map
Map Table
Stand Table
16
15
MapID Area
(ha)
Perimeter
(m)
StandID
14 1.08 416 J-234
15 0.75 350 J-129
16 0.31 223 J-143
17 1.38 523 J-888
Stand
Number
Dominant
Species
Stand
Age
J-127 Hemlock 25
J-316 White Pine 34
J-129 Hemlock 65
J-411 Spruce 34
14
17
Relational DBMS (Contd..,)

26.  Relation (a table) is a collection of similarly shaped
tuples/records (having the same named attributes).
Tuples are records or rows with attribute values.
 Attribute (a column) is characteristic of the relation of a
named field of a tuple.
 The primary key of a relation has one or more attributes
that uniquely identifies a tuple (record).
 Foreign key is used to refer between records of different
relations.
 It is not a key of the relation in which it appears but is
a primary key of another relation.
Relations, Tuples and Attributes

27. THANK YOU