Geography: Class 12 (Part 3) — Chapter 4: Spatial Information Technology

Introduction to Spatial Information Technology

The disciplines that deal with the principles and methods of data processing and mapping using a combination of computer hardware and application software are referred to as Database Management System (DBMS) and Computer Assisted Cartography. Spatial Information Technology relates to the use of technological inputs in collecting, storing, retrieving, displaying, manipulating, managing, and analysing spatial information. It is an amalgamation of Remote Sensing, GPS, GIS, Digital Cartography, and Database Management Systems.

What is GIS (Geographical Information System)?

A Geographical Information System (GIS) is defined as a system for capturing, storing, checking, integrating, manipulating, analysing, and displaying data which are spatially referenced to the Earth. It involves a spatially referenced computer database and appropriate applications software.

Forms of Geographical Information

Geographical information is represented by two types of data: spatial data and non-spatial data (also called attribute data). Spatial data are characterised by their positional, linear, and areal forms of appearances.

Box 4.1: Spatial and Non-Spatial Data Examples

Stock Register of a Cycle Shop (Non-Spatial Data)			Literate Population in States 1981 (Spatial Data)
Part No.	Quantity	Description	State	% Male	% Female
101435	54	Wheel Spoke	Kerala	75.3	65.7
108943	68	Ball Bearing	Maharashtra	58.8	34.8
105956	25	Wheel Rim	Gujarat	54.4	32.3
123545	108	Tyre	Punjab	47.2	33.7

Advantages of GIS over Manual Methods

Traditional maps have limitations such as fixed presentation formats, single or predetermined themes, and the requirement to redraw the entire map for any information updates. GIS offers several inherent advantages:

Users can interrogate displayed spatial features and retrieve associated attribute information.
Maps can be dynamically drawn by querying or analysing attribute data.
Spatial operations like polygon overlay or buffering can be applied to generate new information.
Different items of attribute data can be associated through a shared location code.

Components of GIS

The important components of a Geographical Information System include:

Hardware: Processing, storage, display, and input/output sub-systems.
Software: Modules for data entry, editing, maintenance, analysis, transformation, manipulation, and display.
Data: Spatial and related tabular data (the backbone of GIS).
People: Users ranging from software engineers to environmental scientists and policy-makers.
Procedures: Methods for data retrieval, input, storage, management, analysis, and presentation.

Spatial Data Formats

Spatial data are represented in two primary formats: Raster Data Format and Vector Data Format.

Raster Data Format

Raster data represent graphic features as a pattern of grids of squares (cells). Each cell is assigned a position and an attribute value. The relationship between cell size and the number of cells is expressed as the resolution of the raster.

Grid Resolution Examples:$$50\text{m pixel} \implies 20 \times 16 = 320\text{ pixels}$$$$25\text{m pixel} \implies 40 \times 36 = 1440\text{ pixels}$$

Vector Data Format

Vector data represent objects as points, lines, and polygons using precise coordinate pairs $(X, Y)$ or $(X, Y, Z)$. It is highly precise and ideal for individual map feature analysis.

Comparison of Raster and Vector Data Formats

Model Type	Advantages	Disadvantages
Raster Model	Simple data structure Easy and efficient overlaying Compatible with satellite imagery High spatial variability is efficiently represented	Inefficient use of computer storage Errors in perimeter and shape Difficult network analysis Inefficient projection transformations
Vector Model	Compact data structure Efficient for network analysis Efficient projection transformation Accurate map output	Complex data structure Difficult overlay operations High spatial variability is inefficiently represented Not compatible with satellite imagery

Sequence of GIS Activities

The standard workflow involved in GIS-related work includes:

Spatial Data Input: Acquiring digital datasets or creating them via manual input (digitisation/scanning).
Entering of Attribute Data: Defining non-spatial properties of spatial entities.
Data Verification and Editing: Identifying and correcting errors like data omissions, under/over shoots, and distortions.
Spatial and Attribute Data Linkages: Matching datasets using Exact Matching, Hierarchical Matching, or Fuzzy Matching.
Spatial Analysis: Processing data to extract meaningful geographic insights.

Spatial Analysis Operations

The analytical power of GIS is demonstrated through key spatial operations:

Overlay Analysis Operations

Overlay analysis integrates multiple thematic layers of maps of the same area to obtain a new map layer. It is widely used for land use/land cover change analysis and suitability modeling.

Overlay Equation:$$x + y = z$$Where $x = \text{Road map}$, $y = \text{Rail map}$, and $z = \text{Transportation map}$ (using the spatial overlay union operation).

Buffer Operation

Buffer operation creates a zone of a specified distance around any point, line, or area feature. It is used in proximity analysis to determine areas of influence, service coverage, or environmental impact zones.