(SEM V) THEORY EXAMINATION 2022-23 GIS AND ADVANCE REMOTE SENSING

SECTION A – Short Answer Type Questions (2 Marks each)
 

(a) Differentiate Between Vertical Photograph and Aerial Photograph.

Summary: Vertical photographs are a subset of aerial photographs primarily used in mapping and surveying applications due to their geometric accuracy.

(b) Define Stereoscopic Parallax.

Stereoscopic Parallax is the apparent displacement of an object when viewed from two different positions — typically from two overlapping aerial photographs.

In photogrammetry, this displacement allows measurement of height differences (elevations) between ground points.

It is directly proportional to the height of an object above the mean ground level.

Mathematically:

p=xL−xRp = x_L - x_Rp=xL​−xR​

where xLx_LxL​ and xRx_RxR​ are the image coordinates on the left and right photographs respectively.

Importance: Used in stereoscopic plotting instruments for creating 3D terrain models and topographic maps.

SECTION B – Long Answer Type Questions (10 Marks each)

(a) Describe the Various Atmospheric Windows Used in Remote Sensing.

Atmospheric Windows are specific wavelength ranges of the electromagnetic spectrum that are least absorbed by the atmosphere and therefore suitable for remote sensing.

Key Windows:

Visible Window (0.4 – 0.7 µm):

Detects reflected sunlight.

Used for vegetation, soil, and water body mapping.

Near Infrared (0.7 – 1.3 µm):

Sensitive to vegetation health and moisture content.

Commonly used in NDVI (Normalized Difference Vegetation Index).

Thermal Infrared (8 – 14 µm):

Measures emitted radiation; used for surface temperature mapping and geothermal studies.

Microwave Window (1 mm – 1 m):

Least affected by clouds or atmosphere.

Used in RADAR and SAR (Synthetic Aperture Radar) for all-weather imaging.

Significance:
Atmospheric windows enable satellites like Landsat, MODIS, and Sentinel to collect precise data for environmental monitoring, land-use analysis, and disaster management.

(b) Explain the Different Components of GIS in Detail.

Geographical Information System (GIS) is an integrated framework for capturing, storing, analyzing, and displaying spatial and non-spatial data.

Main Components:

Hardware:

Computers, scanners, digitizers, GPS, and plotters for data collection and visualization.

Software:

GIS applications such as ArcGIS, QGIS, MapInfo that manage spatial databases and perform spatial analysis.

Data:

Core of GIS, includes:

Spatial Data: Maps, satellite images, topography.

Attribute Data: Non-spatial information like name, type, population, etc.

People:

GIS analysts, surveyors, programmers, and decision-makers who operate and interpret results.

Methods:

Standardized procedures for data input, analysis, and output to ensure accuracy and consistency.

Conclusion:
All these components interact dynamically to enable GIS as a powerful decision-support tool in urban planning, disaster management, and environmental studies.

SECTION C – Very Long Answer Type Questions (10 Marks each)

(a) Describe in Detail the Spatial Data and Attribute Data and the Process to Join Both.

Spatial Data:
Represents the geometric features of real-world objects such as points, lines, and polygons.
Examples:           Points – wells, towers.

Lines – roads, rivers.                               Polygons – cities, lakes, land parcels.

Attribute Data:
Describes the non-spatial characteristics (qualitative or quantitative) of spatial features.
Example: A city (polygon) has attributes like population, literacy rate, and area.

Joining Process:

Key Field Selection: Each spatial entity must have a unique ID (like feature ID or primary key).

Join Operation: The attribute table is linked to the spatial data table through this key.

Display: The combined dataset allows mapping and spatial analysis based on attributes (e.g., population density map).

Importance:

Enables integrated spatial analysis.

Used for thematic mapping and decision-making in urban planning, agriculture, and resource management.

(b) Explain the Various Types of Map Projection Systems with Neat Sketch.

Definition:
Map projection is the mathematical transformation of Earth’s curved surface (3D) into a flat map (2D).

Main Types:

Cylindrical Projection: The Earth is projected onto a cylinder.

                                                                              Example: Mercator Projection.

Uses: Navigation and equatorial regions mapping.

Conical Projection:

Projection onto a cone placed over the Earth.

                                                                             Example: Lambert’s Conformal Conic.

Uses: Mid-latitude regions (USA, Europe).

Azimuthal (Planar) Projection:

Projection onto a flat plane touching the globe.

                                                                             Example: Polar Stereographic Projection.

Uses: Mapping polar areas and air route planning.

Distortion Considerations:
Each projection distorts one or more of the following:   Shape (Conformal Projection)

Area (Equal-Area Projection)                                            Distance (Equidistant Projection)

Direction (Azimuthal Projection)

Conclusion:
Choice of projection depends on purpose, geographic extent, and required accuracy in representing Earth’s surface.