1.Introduction to GIS

1. 1 What it is?

1.2  What it does?

1.3  Areas of GIS Applications

1.4  Whats Special about GIS?

1.5  How it works?


R1. GIS Resources on the Web


1. Introduction to GIS


1.1   What it is?


An information system that is designed to work with geographically referenced data (or geospatial data)


GIS organizes the information about place by layers


Any phenomenon can be represented as a layer since all things occur in a certain location and in a certain point of time. To put the world into the computer, we need an abstraction process that transforms real-world entities into mathematically manageable objects. We use basic shapes such as point, line and polygon to effectively capture the spatial components. Spatial objects contain the information about location such as latitude and longitude, as well as topology.


In GIS, spatial objects are linked to attributes


Each spatial object is associated with its attributes. For example, a road has descriptive information such as the number of lane, traffic flow, management agency, and pavement condition, as well as the spatial components. By linking spatial objects to attributes, we can have a better understanding of themes in hand. GIS organizes information such that it pivots around spatial components.


# A system for capturing, storing, retrieving, manipulating, analyzing, and displaying data which are spatially referenced to the Earth -- Chorley, 1987


# A database system with specific capabilities for spatially-referenced data, as well as a set of operations for working [analysis] with the data -- Start and Estes, 1990


# Components of GIS: software, hardware, data, people, training (ESRI)


# GIS as a multidisciplinary science: GIS is an integrated multidisciplinary science consisting of the following traditional disciplines.




Remote Sensing




Computer Science


Operations Research


1.2   What it does?


Estimates are that 80% of all data has a spatial component. Data from most sciences can be analyzed spatially.


If what you do involves managing information, and that information can be linked to geographic locations, then GIS can help you organize that information in new ways so that you can make new discoveries and get more out of the information you have.


GIS requires the following functionalities

Text Box:














Desktop GIS lets you create map displays and maps for presentation simply by pointing and clicking. Desktop GIS lets you visualize and analyze information in new ways, revealing previously hidden relationships, patterns, and trends.



1.3   Areas of GIS Applications


Archaeology, agriculture, banking, defense and intelligence, electric and gas, engineering- pipeline, engineering- surveying, federal government, fire/EMS/disaster/homeland security, forestry, health and human services, insurance, education, landscape architecture, law enforcement and criminal justice, libraries and museums, location service, marine/cost/oceans, media, mining/earth science, natural resources, petroleum, real estate, retail business, state and local government, telecommunications, transportation, universities, and water/wasterwater


The application of GIS is only limited by the imagination of those who use it. --Jack Dangermond, ESRI founder


Network solutions


Ecosystem management


3D mine with well data

Environmental monitoring toxic plume


Site location and client distance


Modeling of future trends



1.4   Whats Special about GIS?


# Integration: Most problems facing the world today – environmental, economic, political, or social – exist in a geographic context. GIS puts various themes all together. Besides, GIS does not restrict data format – it allows you to work on feature data (e.g., shapefiles), image data (e.g., satellite image), and tabular data altogether.




# Visualization: Descriptive attributes may not be easy to interpret. On the contrary, maps are worth a thousand words. GIS is an effective means of communications.



1.5   How it works? [Term definition for ArcView]


# Map Features

The objects represented on maps, whether natural or man-made, are called map features, or simply features. Each map feature has a location, a representative shape, and a symbol that represents one or more of its characteristics. We call the relationships between feature locations spatial relationships, which are important because understanding them helps us solve problems.


To represent real-world entities, maps use three basic shapes – points, lines, and areas (commonly referred to as points, lines, and polygons in a GIS). Any objects can be represented using one of these shapes. We call these shapes feature types.

- Points (e.g., Schools, train stations, fire stations, and buildings in small scale)

- Lines (e.g., Highways, railroads, bridges, and creeks)

- Polygons (e.g., Parks, lake, and buildings in large scale)


The scale of a map tells how the size of the map features compares with the size of the geographic objects they represent. Depending on the map scale, a feature such as a city can appear as a point or as a polygon. As well as shapes, a symbol characterizes map features. (e.g., color, shade, thickness, and marker)


# Attributes

The information that GIS store about map features is referred to as attribute information, or attributes. GIS formats attributes in rows and columns, and stores them as tables. Each column stores a different attribute and each row relates to a single feature.


The link between map features and their attributes is the basic principle behind how GIS work, and is the source of its power. Once the map features and attributes are linked, you can access the attributes for any map features or locate any feature from its attributes in a table. It can also display features based on any attributes in the table.


# Themes

Desktop GIS links sets of features and their attributes and manages them together in units called themes. (Themes are the ArcView specific term; they are named differently in other GIS softwares; for example, Arc/Info uses the term Coverages; Sometimes it is called Layer) A theme contains a set of related features, such as roads, streams, parcels, or wildlife habitat areas, along with the attributes for those features.


# GIS database

All the themes for a geographic area taken together make up a GIS database (often called spatial database). You can use the themes in a GIS database to analyze multiple situations and solve multiple problems.



R1. GIS Resources on the Web


R1.1 GIS faq



R1.2 GIS Dictionary




R1.3 Data Sources








R1.4 GIS Researches and Applications





R1.5 GIS Web Resources






R1.6 ESRI Web Site