GIS SPATIAL ANALYSIS
1
SYLLABUS
Database models, Data storage, Vector data storage,
Attribute data storage, Overview of the data manipulation and
analysis, Integrated analysis of the spatial and attribute data,
Basics of global positioning system.
2
Data Models
Data models are the conceptual models that describe the
structures of databases.
Structure of a database is defined by the data types, the
constraints and the relationships for the description or storage of
data
3
Database model
A database model is the application of a data model when used
in conjunction with a database management system
A database model is classified into three types,
Object based model
Record based model
Physical model
4
Object based Model
These models show the entities attributes and relationships
between them. Object based database model can be classifies
into two categories
Entity relationship model
Object oriented model
5
Entity relationship model
It is used to provide an overall, conceptual view of the
organization of data in a database
A relationship captures how two or more entities are related
to one another
Example a supervise is a relation between a supervisor and his
sub ordinates, a perform is relation between an artist and a
song, proved is a relation between a mathematician and a
theorem
6
Object oriented model
In this model, a information is represented in the form of
objects like in object oriented programming
In this model data defined in terms of a series of unique
objects which are organized into similar phenomena
Relationship between different objects and different classes
are established through explicit links
Example, in application areas such as engineering and spatial
databases (GIS) telecommunication, in scientific areas such
as high energy physics and molecular biology
7
Record based model
In this model a database is composed of some fixed format
records each defining a fixed number of fields of fixed length
Hierarchical model
Network model
Relational model
8
Hierarchical model
It is the earliest database model that is evolved from file system
where records are arranged in a hierarchy or as a tree structure.
Records are connected through pointers that store the address of
the related record. Each pointer establishes a parent child
relationship where a parent can have more than one child but a
child can only have one parent. There is no connection between
the elements at the same level. To locate a particular record, you
have to start at the top of the tree with a parent record and trace
down the tree to the child.
9
10
Advantages
Easy to understand: The organization of database parallels a family
tree understanding which is quite easy.
Accessing records or updating records are very fast since the
relationships have been predefined.
Disadvantages
Large index files are to be maintained and certain attribute values
are repeated many times which lead to data redundancy and
increased storage.
The rigid structure of this model doesn’t allow alteration of tables,
therefore to add a new relationship entire database is to be
redefined.
11
Network Data Structure Model
A network is a generalized graph that captures relationships
between objects using connectivity. A network database consists
of a collection of records that are connected to each other
through links. A link is an association between two records. It
allows each record to have many parents and many children thus
allowing a natural model of relationships between entities.
12
13
Advantages
The many to many relationships are easily implemented in a
network data model.
Data access and flexibility in network model is better than that in
hierarchical model. An application can access an owner record and
the member records within a set .
The model eliminated redundancy but at the expense of more
complicated relationships.
Disadvantages
The network model has a complex structure that requires
familiarity from user’s as well as programmer’s end.
14
Relational Data Structure Model
A flat file structure is used with a relational database model. In this
arrangement, data is stored in different tables made up of rows and
columns. The columns of a table are named by attributes. Each row in
the table is called a tuple and represents a basic fact. No two rows of
the same table may have identical values in all columns.
There are two crucial data integrity constraints viz. primary key and
foreign key. A primary key is an attribute whose value is unique across
all tuples (rows) in a relation (table). The primary key of one table
appearing as an attribute of another table is known as a foreign key in
that table
15
16
Advantages
The manager or administrator does not have to be aware of
any data structure or data pointer. One can easily add, update,
delete or create records using simple logic.
Disadvantages
A few search commands in a relational database require more
time to process compared with other database models
17
Physical Model
A physical database model is a representation of data design
which takes into account the facilities and constraints of given
DBMS
It shows all table structures including column name, column
data type, column constraints primary key, foreign key and
relationships between tables
This model usually used to calculate storage estimates and may
include specific storage allocation details for a given database
system
18
Data Storage
Hybrid data model
Integrated data model
19
Hybrid data model
20
In this model, the topological data and coordinate data are
stored in one file system and the corresponding attribute table
data are in another file system.
For example, the ARC in ARC/INFO GIS software contains the
topological and coordinate data files and INFO contains
attribute tables.
These two data files can be linked or hybridised by means of a
software linkage mechanism.
21
To implement the hybrid vector GIS model, the coordinate and
topological data required for graphics are stored as a separate set
of files.
The attribute tables carrying all the necessary attribute data for
each graphic entity are also stored separately within existing
DBMS software.
Linkage is performed by storing identification codes as a column
data (primary key) in the attribute data base
22
Integrated Data Model
23
The integrated data model which is more closely integrated with
the database management system than in the hybrid system.
The integrated data model approach is also described as the
spatial data base management system approach, with the GIS
serving as the query processor sitting on top of the database
itself.
The integrated data model has a number of implications in
terms of the special characteristics of spatial data.
24
From the data base viewpoint, it is possible to store both the
coordinates and the topological information required to
characterise digital cartographic elements using a design based
on Codd‘s Normal Forms. (x, y) coordinate pairs for individual
vertices along line segments are stored as different rows in a data
base table
25
To achieve satisfactory retrieval performance it has been found
necessary to store coordinate strings in long or 'bulk data'
columns in tables. Handling of large spatial databases is the
need to convert 2-D coordinate information into 1-D spatial keys
that can be stored as data base table columns.
These can then be indexed in the normal way and used for fast
retrieval of map elements contained within or overlapping a
specified geographical search area.
26
Network Analysis
27
Network Analysis
The movement of people the transportation and distribution of
goods and services such as street network, telephone cable
network, pipelines drainage, etc, the delivery of resources and
energy and the communication of information all occur through
definable network system.
28
Types of Network Analysis
Network tracing
Network routing
Network allocation
29
Surface Analysis
30
Types of surface analysis
Deriving contours / Isolines
Deriving slopes
Deriving aspect
Hillshade analysis
Viewshed analysis
Watershed analysis
Surface interaction
31
Deriving Contours / Isolines
32
Deriving Slopes
33
Deriving Aspect
34
Hillshade Analysis
35
Viewshed Analysis
36
Watershed Analysis
37
Database Management System
38
Database
A database is a collection of logically related data. It represents
an aspect of a real world and is designed, built or populated with
data for a specific purpose. Many databases exist for many
applications, and each one of them is maintained by a collection
of programs known as a database management system
39
DBMS
A database management system (DBMS) is a computer program
that stores and manages large amounts of data. One can define,
construct, edit and share the database among various users and
applications.
40
DBMS which makes things easy for the user to create a database
and to maintain it
Maintaining a database involves performing the various data
manipulation operations on the tables in databases. The
operation such as
Adding records
Querying
Modifying records
Deleting records
41
Examples of DBMS
Microsoft Access
Oracle
Sybase
SQL server
DB2
42
Advantages of DBMS
Controlling Redundancy
Restricting Unauthorized Access
Providing Storage Structures for Efficient Query Processing
Providing Backup and Recovery
Enforcing Integrity Constraints
43
Controlling Redundancy
Redundancy means storing the same data multiple times.
DBMS checks redundancy and prevents duplication of
efforts, saves storage space and preserves the data files from
becoming inconsistent.
44
Restricting Unauthorized Access
A DBMS provides a security and authorization system,
which the database administrator uses to create accounts
and to specify account restriction.
45
Providing Storage Structures for Efficient Query Processing
Database systems provide capabilities for efficient execution of
queries and updates. Because the database is typically stored on
disk, it provides specialized data structures to speed up disk
search for the desired records. Auxiliary files called indexes are
used for this purpose.
46
Providing Backup and Recovery
The backup and recovery subsystem of the DBMS helps in
recovering from hardware or software failures.
47
Enforcing Integrity Constraints
Most database applications have certain integrity constraints
that must be held for the data. A DBMS should provide
capabilities for defining and enforcing these constraints.
48
Functions of DBMS
Data definition
Data manipulation
Data security and integrity
Data recovery and concurrency
Data dictionary maintenance
49
Data definition
The provides function to define the structure of the data in the
application. These include defining and modifying the record
structure the type and size of fields and the various
constraints/conditions to be satisfied by the data in each field
50
Data Manipulation
Once data structure is defined data needs to be inserted
modified or deleted. The function which perform these
operation are also part of the DBMS. These functions can handle
planned and unplanned data manipulation needs. Planned
queries are those which form part of application.
51
Data Security and integrity
The DBMS contains function that handle the security and
integrity of data in the application.
These can be easily invoked by the application and hence the
application programmer need not code these function in his/her
programmes
52
Data recovery and concurrency
Recovery of data after a system failure and concurrent access of
records by multiple user also handled by the DBMS
53
Data Dictionary Maintenance
Maintaining the data dictionary which contains the data
definition of the application is also one of the function of a
DBMS
54
Architecture
55
External Level refers to user’s view of the database. It describes
a part of the database for particular group of users. Depending
on their needs, different users access different parts of the
database. It employs a powerful and flexible security mechanism
by hiding parts of the database from certain users.
Conceptual Level refers to the logical structure of the entire
database. It describes data as well as the relationships among the
data.
Internal Level refers to the details of physical storage of the
database on the computer. It consists of description of storage
space allocation for data and indexes, record placements and
data compression.
56
