Introduction to GISBY : EHSAN HAMZEI - 810392121

GIS ?

Everyone has their own favorite definition of a GIS, and there are many to choose from.

Ex: A container of maps in digital form (The general public) A mechanized inventory of geographically distributed features

and facilities. (Utility managers, transportation officials, resource managers)

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GIS ?

A geographic information system (GIS) is a computer-based information system that enables capture, modelling, manipulation, retrieval, analysis and presentation of geographically referenced data.

Two of the most important technologies underlying GIS are database systems and computer graphics.

One way of understanding GIS is to look at its application.

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Schematic of a GIS 3

Schematic of a GIS 4

At the heart of any GIS is the database. The data that are held in the database are given context and meaning by the application domain(s) and then take on an informational value.

Data are only useful when they are part of a structure of interrelationships that forms the context of the data. Such a context is partly provided by the data model.

GIS Vs. Traditional IS 5

Most traditional IS, require only limited presentational forms, usually based around tables of data, numerical computation and textual commentary.

But in GIS, the spatial nature of the information allows a whole new range of possibilities, including cartographic forms and visualization techniques.

Why Does GIS Matter?

Almost everything that happens, happens somewhere. Knowing where something happens can be critically important.

Problems that involve an aspect of location, either in the information used to solve them or in the solutions themselves, are termed geographic problems. Ex (where to locate new Clinic)

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Classification of Geographic Problems

Based On:

Scale

Purpose

Time Scale

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Classification of Geographic Problems

1- Scale or level of geographic detail is an essential property of any GIS project.

2- Some problems are strictly practical in nature, But others are better characterized as driven by human curiosity. The Difference Between them is Purpose! (Normative Vs. Positive)

3- Time Scale for different Problem, Widely changed ! (Ex: Geomorphologic Problem Vs. Traffic Problems)

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Why GIS is Special?

1- Multidimensional 2- Voluminous 3- Time Consuming to Analyze 4- Complex and Expensive (Update) 5- Multi Resolution representation

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Geospatial Vs. Geographic

Geographic : Geographic refers to the Earth surface and near surface

Spatial : Spatial refers to any space not only the space of the Earth’s surface;

Geospatial : implying a subset of spatial applied specifically to the Earth’s surface and near surface.

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Decision-making support infrastructure

Wisdom

Knowledge

Evidence

Information

Data

Ease of sharing - Impossible

Ease of sharing - Easy

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Knowledge Vs. Information

3 Important Difference:

1- Knowledge entails a knower 2- Knowledge is harder to detach from the knower than

information 3- Knowledge requires much more assimilation – we digest it

rather than hold it

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Knowledge

2 Type: 1- codified

2- tacit

Knowledge about how the world works is more valuable than knowledge about how it looks, because such knowledge can be used to predict. (Idiographic Vs. Nomothetic)

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History of GIS

The first GIS was the Canada Geographic Information System, designed in the mid-1960s

ODYSSEY GIS of the late 1970s The first automated cartography developments occurred in the

1960s The modern history of GIS dates from the early 1980s, when the

price of sufficiently powerful computers fell below a critical threshold

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Anatomy of a GIS 15

Data 16

1- Correctness and accuracy

2- Timeliness, relevance and cost

3- Usability and accessibility

Database 17

For a database to be useful it must be: 1- Secure 2- Reliable 3- consistent 4- Technology proof

Processing Requirement 18

1- Geometric and topological analyses, Ex: Proximity

2- Fields, surfaces and layers, Ex: Aspect

3- Network analysis, Ex: Shortest path

Hardware 19

major functional components of a computer

Hardware 20

Input Devices :

Communications 21

Only in the ideal world is it the case that the signal transmitted is equal to the signal received, In the real world degradations occur:

1- Attenuation 2- Delay 3- Noise

Communications 22

Networks: 1- wide-area network (WAN): a network of computers spread over

a large area.

2- A local-area network (LAN): a network of computers spread over a small area.

Communications 23

Client-server computing: Client-server computing is a form of distributed computing in

which some stations act as servers and some as clients. A server holds data and services available for transmission to

other stations, clients, in the network.

Communications 24

Type of Messages in Client-Server Architecture: requests from client to server. replies from server to client. events from server to client. errors.

The Business of a GIS 25

1- Software Industry 2- Data Industry 3- GI Service Industry 4- Publishing Industry 5- GIS Education

Thanks 26