NCERT Solutions for Class 12 Geography Practical Work in Geography II Chapter 4: Spatial Information Technology

Chapter at a glance

Exercise Questions

Question 1 (i)

The spatial data are characterised by the following forms of appearance:
(a) Positional (b) Linear (c) Areal (d) All the above forms

Answer

Spatial data appear in three forms: positional (point), linear (line) and areal (polygon).

4. All the above forms

Question 1 (ii)

Which one of the following operations requires analysis module software?
(a) Data storage (b) Data display (c) Data output (d) Buffering

Answer

Buffering (creating zones of specified distance around features) is a spatial analysis operation that requires the analysis module of GIS software; storage, display and output are basic functions.

4. Buffering

Question 1 (iii)

Which one of the following is disadvantage of Raster data format?
(a) Simple data structure (b) Easy and efficient overlaying (c) Compatible with remote sensing imagery (d) Difficult network analysis

Answer

Simple structure, easy overlaying and compatibility with remote sensing images are advantages of raster data. Network analysis is difficult in raster format — a disadvantage (along with large storage and less precise boundaries).

4. Difficult network analysis

Question 1 (iv)

Which one of the following is an advantage of Vector data format?
(a) Complex data structure (b) Difficult overlay operations (c) Lack of compatibility with remote sensing data (d) Compact data structure

Answer

Vector data have a compact data structure (less storage), accurate graphics and efficient network analysis — advantages. Complex structure, difficult overlays and incompatibility with remote sensing are disadvantages.

4. Compact data structure

Question 1 (v)

Urban change detection is effectively undertaken in GIS core using:
(a) Overlay operations (b) Proximity analysis (c) Network analysis (d) Buffering

Answer

Overlay operations superimpose layers of different dates (e.g. land use of 1990 and 2020) to detect changes such as urban expansion.

1. Overlay operations

Question 2 (i)

Differentiate between raster and vector data models.

Answer

Raster data represent space as a grid of cells with values (simple, good for overlay and remote sensing, but bulky and less precise); vector data represent features as points, lines and polygons with coordinates (compact and precise, good for networks, but complex and harder to overlay).

Question 2 (ii)

What is an overlay analysis?

Answer

Overlay analysis is a GIS operation in which two or more thematic layers of the same area (e.g. land use, soils, slope, roads) are superimposed to create a new layer that combines their attributes. It is used to find relationships and suitable sites (e.g. land suitable for a new school), and to detect changes over time (urban change detection).

Overlay analysis superimposes two or more thematic layers of the same area in GIS to produce a combined layer, used for site suitability, finding relationships and detecting changes such as urban growth.

Question 2 (iii)

What are the advantages of GIS over manual methods?

Answer

1. Interactive queries – the user can ask questions and get answers interactively.
2. Integration of spatial (map) and non-spatial (attribute) data, and of data from different sources.
3. Easy updating and modification of data.
4. Quick and accurate analysis – overlay, buffering, network analysis, which are tedious manually.
5. Multiple outputs – maps, graphs, tables of various scales and themes can be produced quickly; “what-if” scenarios.
6. Storage of large volumes of data in digital form.

GIS allows interactive queries, integrates spatial and attribute data from many sources, is easy to update, performs quick and accurate analyses (overlay, buffering, networks), stores large data digitally and produces varied outputs quickly — unlike manual methods.

Question 2 (iv)

What are important components of GIS?

Answer

The important components of GIS are: 1. Hardware – computers, digitisers, scanners, printers, plotters, GPS. 2. Software – GIS packages for input, storage, analysis and output (e.g. ArcGIS, QGIS). 3. Data – spatial data (maps, images, coordinates) and attribute (non-spatial) data. 4. People (users) – trained professionals who manage the system and analyse data. 5. Methods/procedures – well-designed plans and rules for operations.

The components of GIS are hardware, software, data (spatial and attribute), people (trained users) and methods/procedures.

Question 2 (v)

What are different ways in which spatial data is built in GIS core?

Answer

Spatial data can be entered into GIS by: 1. Digitisation – manual digitisation of existing maps using a digitiser, or on-screen digitisation. 2. Scanning of maps and converting them (raster), followed by vectorisation. 3. Remote sensing data – satellite images and aerial photographs. 4. GPS (Global Positioning System) and field surveys – recording coordinates directly. 5. Importing existing digital data from other sources (e.g. Survey of India, Census databases).

Spatial data are built in GIS by digitising maps, scanning and vectorising them, importing remote sensing images and aerial photographs, collecting coordinates by GPS and field surveys, and importing existing digital datasets.

Question 2 (vi)

What is Spatial Information Technology?

Answer

Spatial Information Technology relates to the use of technological inputs in collecting, storing, retrieving, displaying, manipulating, managing and analysing spatial (location-based) information. It is an amalgam of remote sensing, GPS, GIS, digital cartography and database management systems.

Spatial information technology is the use of technology — remote sensing, GPS, GIS, digital cartography and databases — to collect, store, retrieve, display, manipulate, manage and analyse location-based information.

Question 3 (i)

Discuss raster and vector data formats. Give example.

Answer

Spatial data in GIS are represented in two formats:

1. Raster data format: - Represents geographical features as a matrix of grid cells (pixels) in rows and columns; each cell has a value representing a feature (e.g. land use type, elevation). - Points are represented by single cells, lines by a series of connected cells, and areas by groups of cells. - Example: satellite images, aerial photographs, scanned maps, digital elevation models. - Advantages: simple data structure; easy and efficient overlay operations; compatible with remote sensing imagery; high spatial variability is efficiently represented; simple for own programming; same grid cells for several attributes. - Disadvantages: inefficient use of computer storage (large files); errors in perimeter and shape (less precise boundaries); difficult network analysis; inefficient projection transformations; loss of information when using large cells; less accurate (although interactive) maps.

2. Vector data format: - Represents features as points (x, y coordinates — e.g. wells, towns), lines (strings of coordinates — e.g. roads, rivers) and polygons (closed areas — e.g. states, lakes, land parcels). - Example: road and railway networks, administrative boundaries, locations of schools and hospitals. - Advantages: relatively low data volume (compact data structure); faster display; less loss of information; efficient network analysis; efficient projection transformation; accurate map output. - Disadvantages: complex data structure; difficult overlay operations; high spatial variability is inefficiently represented; not compatible with remote sensing imagery.

Raster format represents features as a grid of cells (e.g. satellite images, scanned maps); it has a simple structure, easy overlays and remote-sensing compatibility, but large storage, imprecise boundaries and difficult network analysis. Vector format represents features as points (wells), lines (roads, rivers) and polygons (states, lakes); it is compact, precise and good for networks and projections, but complex, harder to overlay and not compatible with remote sensing images.

Question 3 (ii)

Write an explanatory account of the sequence of activities involved in GIS related work.

Answer

The sequence of activities in GIS-related work:

1. Spatial data input – spatial data are entered into the GIS database by digitising existing maps (manual or on-screen), scanning, importing satellite images and aerial photographs, GPS and field survey data, or existing digital files.
2. Entering the attribute data – non-spatial (attribute) data describing the features (e.g. population of a village, name and type of road) are entered, usually in tables, and linked to the spatial features through unique identifiers.
3. Data verification and editing – errors in digitisation (e.g. undershoots, overshoots, unclosed polygons, missing or duplicate features) are checked and corrected; the topology (spatial relationships among features) is built; data are given a common coordinate system/projection.
4. Spatial analysis – the most important part; includes:
   • Overlay analysis – superimposing layers to combine attributes or detect change (e.g. urban change detection);
   • Buffer (proximity) analysis – zones around features (e.g. areas within 1 km of a highway);
   • Network analysis – shortest/optimal route, service areas (e.g. ambulance routes);
   • Queries, measurements, statistical analysis, terrain analysis.
5. Output – results are presented as maps, tables, graphs and reports, on screen or printed, for decision-making.

GIS work proceeds through: (1) spatial data input (digitising, scanning, satellite images, GPS); (2) entering attribute data and linking it to features; (3) data verification and editing, building topology and a common projection; (4) spatial analysis — overlay, buffering, network analysis and queries; and (5) output as maps, tables, graphs and reports.

Topic checklist

• ☒ Spatial information technology and GIS components (Q 1 (i), 2 (iii), 2 (iv), 2 (vi))
• ☒ Raster and vector data (Q 1 (iii), 1 (iv), 2 (i), 3 (i))
• ☒ Data input and GIS operations (Q 1 (ii), 1 (v), 2 (ii), 2 (v), 3 (ii))

Total questions answered: 13 of 13