All exercise questions from the NCERT textbook Practical Work in Geography, Part-II, Chapter 4, “Spatial Information Technology”, exactly as the English edition prints them, with a full model answer for each. Try your own answer first, then check it against this one.
1 Choose the right answer from the four alternatives given below
Q. The spatial data are characterised by the following forms of appearance:
(a) Positional (b) Linear (c) Areal (d) All the above forms
Answer: (d) All the above forms. The chapter states that spatial data are characterised by their positional, linear and areal forms of appearance (Fig. 4.1): all three, not any one alone.
Q. Which one of the following operations requires analysis module software?
(a) Data storage (b) Data display (c) Data output (d) Buffering
Answer: (d) Buffering. The chapter lists three kinds of software modules: for data entry/editing/maintenance, for analysis/transformation/manipulation, and for data display/output. Data storage, display and output are handled by the other two modules, but buffering is a spatial analysis operation, so it needs the analysis module software.
Q. 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: (d) Difficult network analysis. Box 4.2 lists a simple data structure, easy/efficient overlaying and compatibility with satellite imagery as advantages of the raster model; difficult network analysis is listed as one of its disadvantages.
Q. 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: (d) Compact data structure. Box 4.2 lists a complex data structure, difficult overlay operations and lack of compatibility with satellite imagery as disadvantages of the vector model; a compact data structure is listed as one of its advantages.
Q. Urban change detection is effectively undertaken in GIS core using:
(a) Overlay operations (b) Proximity analysis (c) Network analysis (d) Buffering
Answer: (a) Overlay operations. The chapter’s own Aligarh City example detects urban land-use change by overlaying the 1974 and 2001 land-use maps to map the resulting urban sprawl: an overlay operation, not a buffer, network or proximity operation.
2 Answer the following questions in about 30 words
Q. Differentiate between raster and vector data models.
Answer: Raster data represent a feature as a grid of cells (pixels), each with a row/column position and a value. Vector data instead record a feature as coordinates (X,Y or X,Y,Z) of its start and end points, with lines having direction and polygons built from points or lines.
Q. What is an overlay analysis?
Answer: Overlay analysis integrates two or more thematic map layers of the same area to produce a new map layer, similar to sieve mapping. For example, road and rail maps are overlaid (x + y = z) to obtain a combined transportation map.
Q. What are the advantages of GIS over manual methods?
Answer: GIS lets users interrogate spatial features and retrieve attribute data; draw maps by querying attributes; apply spatial operations like overlay or buffering on an integrated database; and associate different attribute items through a shared location code.
Q. What are important components of GIS?
Answer: GIS has five components: Hardware (processing/storage/display/input-output), Software (entry-editing, analysis-transformation, display-output modules), Data (spatial and tabular, the backbone), People (engineers to policy-makers) and Procedures (retrieval to final output).
Q. What are different ways in which spatial data is built in GIS core?
Answer: A GIS core can be built in three ways: acquiring data in digital form from a data supplier, digitising existing analogue data, or carrying out one’s own surveys of geographic entities.
Q. What is Spatial Information Technology?
Answer: Spatial Information Technology is the use of technological inputs to collect, store, retrieve, display, manipulate, manage and analyse spatial information. It is an amalgamation of Remote Sensing, GPS, GIS, Digital Cartography and Database Management Systems.
3 Answer the following questions in about 125 words
Q. Discuss raster and vector data formats. Give example.
Answer: Spatial data are represented in two formats. Raster data represent a graphic feature as a pattern of grids of squares: the image is sub-divided into a matrix of small cells, each cell assigned a position and given a value based on its attribute, and its row/column coordinates identify any individual pixel (e.g. a scanned map or a satellite image, 320 pixels at a 50 m resolution versus 1,440 pixels at a 25 m resolution for the same area). Raster suits digital aerial photographs and satellite images, low-cost applications, and “backdrop” maps that need no individual-feature analysis. Vector data instead record a feature by the coordinates of its points (X,Y or X,Y,Z), for example a road recorded as the coordinates of the points along its length, with lines having direction and polygons built from points or lines; manual digitising is the best input method. Vector suits highly precise applications, small file sizes, individual-feature analysis and storing descriptive information.
Q. Write an explanatory account of the sequence of activities involved in GIS related work.
Answer: GIS-related work follows five activities. Spatial data input brings map geometry into the GIS, either by acquiring ready-made digital data from a supplier (checking its scale, geo-referencing, sampling, quality, classification method, mapping-unit size and record length for compatibility, and transferring it via DAT tape, CD ROM or floppy disk) or by manual input through digitisation or scanning. Entering the attribute data attaches non-spatial properties, such as a road’s width or surface type, to each spatial object. Data verification and editing checks the captured data for three kinds of error: incomplete/double data, wrong-scale data, and distorted data, usually by comparing a computer plot against the original on a light table, then correcting errors with editing tools such as a digitiser tablet or “weeding” algorithms. Spatial and attribute data linkages join the two data types using exact, hierarchical or fuzzy matching. Finally, spatial analysis, chiefly overlay and buffer analysis, transforms the linked database into information useful to decision-makers.