GIS & REMOTE SENSING (KOE-066)
Important Questions & Answers – Section-wise
SECTION A
(Attempt all questions – 2 × 10 = 20 marks)
a. Elements of Remote Sensing
The main elements of remote sensing include energy source, radiation and atmosphere, interaction of energy with earth surface, sensor, platform, data transmission, data processing, and interpretation.
b. Working principle of Remote Sensing
Remote sensing works on the principle of detecting reflected or emitted electromagnetic radiation from earth surface features. The sensor records this energy and converts it into digital data for analysis.
c. Role of sensors in Remote Sensing
Sensors detect electromagnetic radiation reflected or emitted from objects on the earth’s surface. They convert this radiation into electrical signals which are processed to generate images.
d. Types of platforms in Remote Sensing
Remote sensing platforms include ground-based platforms, airborne platforms such as aircraft and drones, and space-borne platforms like satellites.
e. Stereoscopy
Stereoscopy is the technique of viewing two overlapping aerial photographs to obtain a three-dimensional perception of terrain and objects.
f. Fundamental steps in Digital Image Processing
Digital image processing involves image acquisition, preprocessing, enhancement, classification, analysis, and interpretation.
g. Application of microwave remote sensing in defence
Microwave remote sensing is used in defence for surveillance, target detection, terrain analysis, and weather-independent reconnaissance.
h. Why microwave remote sensing is all-weather
Microwaves can penetrate clouds, fog, rain, and dust, making microwave remote sensing effective in all weather conditions.
i. TIN elevation model
TIN (Triangulated Irregular Network) is a vector-based elevation model that represents terrain using irregularly spaced points connected by triangles.
j. Use of ‘clip’ tool in GIS
The clip tool extracts a portion of a spatial dataset using a defined boundary, allowing focused analysis on a specific area.
SECTION B
(Attempt any THREE – 10 × 3 = 30 marks)
Q2(a) Energy interaction with earth surface
When electromagnetic energy strikes the earth’s surface, it is reflected, absorbed, or transmitted. The energy balance equation is:
Incident Energy=Reflected Energy+Absorbed Energy+Transmitted EnergyIncident\ Energy = Reflected\ Energy + Absorbed\ Energy + Transmitted\ EnergyIncident Energy=Reflected Energy+Absorbed Energy+Transmitted Energy
Different materials reflect energy differently, forming the basis of feature identification.
Q2(b) Scale of aerial photograph (Numerical)
Using scale formula:
Scale=f(H−h)Scale = \frac{f}{(H - h)}Scale=(H−h)f
where
fff = focal length
HHH = flying height above datum
hhh = ground elevation
Substituting values gives the required photograph scale.
(In exam: show formula → substitute → final answer)
Q2(c) Stereoscopic parallax
Stereoscopic parallax is the apparent displacement of objects in overlapping photographs due to elevation difference. Height of object is calculated using difference in parallax values.
Q2(d) UTM geographic coordinate system
UTM (Universal Transverse Mercator) divides the earth into 60 longitudinal zones. It uses meters instead of degrees, making it suitable for large-scale mapping.
Q2(e) Data input methods in GIS
GIS data input methods include digitization, scanning, GPS survey, remote sensing data, and importing existing digital databases.
SECTION C
Q3(a) Electromagnetic spectrum
The electromagnetic spectrum includes gamma rays, X-rays, ultraviolet, visible light, infrared, microwave, and radio waves. Remote sensing primarily uses visible, infrared, and microwave regions.
Q3(b) Spectral reflectance curve of vegetation and water
Vegetation reflects strongly in near-infrared region and absorbs red light due to chlorophyll, while water absorbs most radiation and shows low reflectance.
Q4(a) Aerial photograph terminology
Angle of tilt is the inclination of camera axis from vertical. Photo principal point is the intersection of camera axis with photograph. Nadir point is the vertical projection of camera lens. Principal plane contains the camera axis. Horizon point is where principal plane intersects horizon.
Q4(b) Number of photographs required (Numerical)
Number of photos is calculated using area coverage per photograph considering longitudinal and side overlap. Separate calculations are done for given areas.
Q5(a) Push broom vs Whisk broom
Push broom sensors use linear arrays and capture data row by row, while whisk broom sensors use oscillating mirrors. Push broom provides better resolution and stability.
Q5(b) Image classification
Image classification assigns pixels to land-use classes. In supervised classification, training data is used, while unsupervised classification groups pixels automatically based on spectral similarity.
Q6(a) Microwave bands and applications
Microwave bands include L, C, X, and Ku bands. They are used in soil moisture estimation, flood mapping, military surveillance, and weather forecasting.
Q6(b) Map projection
Map projection transforms earth’s curved surface onto a flat map. The main projection techniques are cylindrical, conical, and azimuthal projections.
Q7(a) Spatial data models
Spatial data models include vector and raster models. Vector model is precise and efficient for discrete features, while raster model is suitable for continuous data analysis.
Q7(b) Map overlay
Map overlay combines multiple spatial layers to analyze relationships. Tools like intersect and union are commonly used for overlay operations.
