Introduction To Geographic Information Systems (GIS)

A geographic information system (GIS) integrates hardware, software, and data for capturing, managing, analyzing, and displaying all forms of geographically referenced information.
GIS software represents features on the earth, such as buildings, cities, roads, rivers, and states, on a computer. People use GIS to visualize, question, analyze, and understand this data about the world and human activity. Often, this data is viewed on a map, which provides an advantage over using spreadsheets or databases. Why? Because maps and spatial analysis can reveal patterns, point out problems, and show connections that may not be apparent in tables or text.
GIS uses layers, called "themes," to overlay different types of information, much as some static maps use mylar overlays to add tiers of information to a geographic background. Each theme represents a category of information, such as roads or forest cover. As with the old mylar maps, the layers which are underneath remain visible while additional themes are placed above.

THREE VIEWS OF A GIS :
A GIS is most often associated with a map. A map, however, is only one way you can work with geographic data in a GIS, and only one type of product generated by a GIS.
A GIS can be viewed in three ways:
- The Database View: A GIS is a unique kind of database of the world—a geographic database (geodatabase). It is an "Information System for Geography."
- The Map View: A GIS is a set of intelligent maps and other views that show features and feature relationships on the earth's surface.
- The Model View: A GIS is a set of information transformation tools that derive new geographic datasets from existing datasets.

IMPLEMENTING GIS :
Implementing GIS presents a unique set of challenges. Even the most well-funded projects can fail because of poor planning. 10-stage process for successfully deploying GIS are :
- Consider the strategic purpose.
- Plan for the planning.
- Determine technology requirements.
- Determine the end products.
- Define the system scope.
- Create a data design.
- Choose a data model.
- Determine system requirements.
- Analyze benefits and costs.
- Make an implementation plan.

APPLICATIONS OF GIS ?
Planners of all kinds—business analysts, city planners, environmental planners, and strategists from all organizations—create new patterns or reshape existing ones
every day.
1. Cartographic
- Irrigation
- Crop yield analysis
- Land evaluation
- Planning & Facilities management
- Landscape Studies
- Traffic pattern analysis
2. Digital Terrain Modeling
- Earth science resource studies
- Civil Engineering & military evaluation
- Soil surveys
- Air & Water pollution studies
- Flood control
- Water resource management
3. Geographic Objects Applications
- Car navigation systems
- Geographic market analysis
- Utility distribution & consumption
- Consumer product and services - economic analysis

Conceptual Data Models for Database Design

Conceptual modeling is an important phase in designing a successful database application. The database design process consists of a number of steps listed below:

Step 1: Requirements Collection and Analysis
- Prospective users are interviewed to understand and document data requirements
This step results in a concise set of user requirements, which should be detailed and complete.
- The functional requirements should be specified, as well as the data requirements. Functional requirements consist of user operations that will be applied to the database, including retrievals and updates.
- Functional requirements can be documented using diagrams such as sequence diagrams, data flow diagrams, scenarios, etc.



Step 2: Conceptual Design / Data Modeling
- Once the requirements are collected and analyzed, the designers go about creating the conceptual schema.
- Conceptual schema: concise description of data requirements of the users, and includes a detailed description of the entity types, relationships and constraints.
- The concepts do not include implementation details; therefore the end users easily understand them, and they can be used as a communication tool.
- The conceptual schema is used to ensure all user requirements are met, and they do not conflict.

Step 3: Database Design
- Two sub-steps called Database Logical Design which define a database in a data model of a specific DBMS and Database Physical Design which define the internal database storage structure are defined.
- It also defines file organization or indexing techniques.

Step 4: Database Implementation
- Many DBMS systems use an implementation data model, so the conceptual schema is transformed from the high-level data model into the implementation data model.
- This step is called logical design or data model mapping, which results in the implementation data model of the DBMS.

Step 5: Physical Design
- Internal storage structures, indexes, access paths and file organizations are specified.
- Application programs are designed and implemented.