NCERT Solutions For Class 12 Geography Part C Chapter 4 Spatial Information Technology

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    52. Choose the right answer from the four alternatives given below :

    (i) The spatial data are characterised by the following forms of appearance :

    • (a) Positional
    • (b) Linear
    • (c) Areal
    • (d) All the above forms
    • Ans. (b) Linear

    (ii) Which one of the following operations requires analysis module software?

    • (a) Data storage
    • (b) Data display
    • (c) Data output
    • (d) Buffering
    • Ans. (d) Buffering

    (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
    • Ans. (d) Difficult network analysis

    (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
    • Ans. (d) Compact data structure

    (v) Urban change detection is effectively undertaken in GIS core using:

    • (a) Overlay operations
    • (b) Proximity analysis
    • (c) Network analysis
    • (d) Buffering
    • Ans. (d) Buffering

    53. Answer the following questions in about 30 words :

    (i) Differentiate between Raster and Vector data models.

    Ans. Difference between Raster data model and Vector data model:
    Raster data model Raster data model Vector data model
    1. A graphic feature is a pattern of grids of squares. Vector data represents the object as a set of lines drawn between specific points.
    2. Simple data structure. Compact data structure.
    3. Easy and efficient overlaying. Efficient for network analysis.
    4. Compatible with satellite imagery. Efficient projection transformation.
    5. High spatial variability is efficiently represented. Accurate map output

    (ii) What is an overlay analysis?

    Ans. GIS is known for its overlay analysis operations. An essential analytical function is the integration of many layers of maps utilising overlay techniques. In other words, GIS allows overlaying two or more thematic layers of maps from the same region to create a new map layer, similar to sieve mapping, which involves tracing maps on a light table to compare them and create an output map.

    (iii) What are the advantages of GIS over manualmethods?

    Ans. Separate data storage and presentation are intrinsic advantages of GIS. It also helps to examine and show the data in a variety of ways. The following are some of the most significant benefits of GIS:

    1. Users can analyse presented spatial characteristics by interrogating them and retrieving related attribute information.
    2. By querying or analysing attribute data, maps may be created.
    3. On an integrated database, spatial procedures (polygon overlay or buffering) can be used to produce new sets of data.
    4. Using a common location code, different types of attribute data may be linked together.

    (iv) What are important components of GIS ?

    Ans. The important components of a Geographical Information System include the following:

    1. Hardware
    2. Software
    3. Data
    4. People
    5. Process

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

    Ans. The geographic database into a GIS is known as spatial data input. It may be made from a number of different sources. The following two categories can be used to summarise them:

    1. Purchasing digital data sets from Data Providers: Digital data, ranging from smallscale maps to large-scale blueprints, is now freely available thanks to modern data sources. Many municipal governments and business organisations rely on such data since it relieves them of the costs of digitising or gathering their own information.
    2. Using manual input to create digital data sets: There are four primary phases to manually entering data into a GIS:
      1. Entering the spatial data.
      2. Entering the attribute data.
      3. Spatial and attribute data verification and editing.
      4. Where necessary, linking the spatial to the attribute data.

    (vi) What is Spatial Information Technology ?

    Ans. It refers to the characteristics and phenomena that are dispersed throughout a geographically delimited region and hence have physical dimensions. In other words, Spatial Information Technology uses technical inputs to collect, store, retrieve, present, manipulate, manage, and analyse spatial data.

    54. Answer the following questions in about 125 words :

    (i) Discuss raster and vector data formats. Give example.


    Raster data format Vector data format
    Meaning Raster data format represents a graphic feature as a pattern of grids of squares. Vector data represents the object as a set of lines drawn between specific points.
    Suitability The Raster file formats are most often used for the following activities:
    1. For digital representations of aerial photographs, satellite images scanned paper maps, etc.
    2. When costs need to be kept down.
    3. When the map does not require analysis of individual map features.
    The Vector files are most often used for:
    1. Highly precise applications.
    2. When file sizes are important.
    3. When individual features require analysis.
    4. When descriptive information must be stored.
    Advantage Simple data structure; Easy and efficient overlaying; Compatible with satellite advantage imagery; High spatial variability is efficiently represented. Compact data structure; Efficient for network analysis; Efficient projection transformation.

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

    Ans. In GIS-related activity, the following sequence of actions is involved:

    1. Spatial data input: Under this procedure, data received from various persons is analysed to see if it is suitable for the investigator.
    2. Entering attribute data: Attribute data specify the non-spatial attributes of a geographic item that need to be handled in the GIS. A road, for example, might be represented in the spatial section of the GIS by a specific colour, symbol, or data location and recorded as a group of contiguous pixels or as a line object.
    3. Data verification and editing: The spatial
      data recorded in a GIS must be verified for mistake detection and fixes to maintain data correctness. Data omissions and under/ overshoots are two examples of digitisation problems. The easiest technique to check for inaccuracies in spatial data is to create a computer plot or print the data at the same scale as the original, ideally on a transparent sheet.
    4. Geographical and attribute data links: In GIS, spatial and attribute data linkages are critical. As a result, it must be approached with caution. When attribute data is linked to non-related spatial data, the result will be chaos in the final data analysis. Similarly, the matching of one data layer with another is crucial.
    5. Spatial analysis: The goal of geographic analysis is to turn data into valuable information that meets the needs of decisionmakers. To conclude, step-by-step methods are required. GIS may be used to perform the following geographic analytic operations: 

    (i) Overlay analysis

    (ii) Buffer analysis

    (iii) Network analysis

    (iv) Digital terrain model

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