GIS & REMOTE SENSING – KOE066
Section-wise Important Questions & Ready Answers
SECTION A
(Attempt all questions in brief – 2 marks each)
(a) Disadvantages of Remote Sensing
Remote sensing depends on atmospheric conditions such as clouds, haze, and rain, which can affect data quality. High initial cost, requirement of skilled interpretation, and limited resolution for some sensors are also major disadvantages.
(b) Use of Remote Sensing for Water Resources
Remote sensing helps in mapping surface water bodies, monitoring reservoirs, assessing groundwater potential, flood forecasting, drought assessment, and watershed management through satellite imagery.
(c) Types of Aerial Photographs
Aerial photographs are classified as vertical photographs, low oblique photographs, and high oblique photographs based on the orientation of the camera axis.
(d) Scale of the Map (Numerical)
Actual distance = 200 km = 20,000,000 cm
Map distance = 10 cm
Scale = 10 : 20,000,000
= 1 : 2,000,000
(e) Features on a Vertical Aerial Photograph
Vertical aerial photographs show uniform scale, minimal distortion, clear representation of ground features such as roads, rivers, buildings, vegetation, and landforms.
(f) Causes of Relief Displacement
Relief displacement is caused due to terrain height variation, camera tilt, and radial displacement from the principal point of the photograph.
(g) Main Components of GIS
The main components of GIS are hardware, software, data, people, and methods, all working together to capture, store, analyze, and display spatial data.
(h) Entities of Spatial Data
Spatial data entities include points, lines, and polygons, which represent features like wells, roads, and land parcels respectively.
(i) Encoding Methods for Different Data Sources
Encoding methods include manual digitization, scanning, GPS-based data capture, and remote sensing image classification to convert real-world data into digital GIS format.
(j) Linking Spatial and Attribute Data in GIS
Spatial data is linked to attribute data using a unique identifier such as an ID field, enabling descriptive information to be associated with geographic features.
SECTION B
(Attempt any three – 10 marks each)
2(a) Significance of Electromagnetic Radiation (EMR) in Remote Sensing
EMR is the fundamental energy source in remote sensing. Sensors detect reflected or emitted EMR from the Earth’s surface. Different wavelengths interact differently with objects, allowing identification of land, water, vegetation, and soil. Understanding EMR helps in sensor selection and image interpretation.
2(b) Characteristics of EMR Interaction with Soil Particles
EMR interaction with soil depends on moisture content, texture, organic matter, and roughness. Dry soils reflect more energy, while moist soils absorb energy, especially in infrared wavelengths. Soil color and composition also influence reflectance patterns.
2(c) Image Parallax and Stereoscopic Viewing
Parallax is the apparent shift in position of an object between two overlapping aerial photographs. It is used to determine height and depth. Stereoscopic viewing uses two photographs to create a three-dimensional view of terrain. (Diagram explanation expected in exam)
2(d) Microwave Remote Sensing for Tropical Rainforests
Microwave remote sensing penetrates clouds, rain, and dense vegetation, making it ideal for monitoring tropical rainforests. Unlike optical sensors, microwave sensors operate day and night and provide reliable data in humid regions.
2(e) Encoding Methods for Different Data Sources
Vector data is encoded using points, lines, and polygons, while raster data uses grid cells. Data sources such as maps, satellite images, GPS data, and surveys are encoded using digitization, scanning, and image classification techniques.
SECTION C
3(a) Active vs Passive Remote Sensing Systems
Active remote sensing systems transmit their own energy and measure the reflected signal, such as RADAR and LiDAR. Passive systems rely on natural energy sources like sunlight or Earth’s thermal emission, such as optical and thermal sensors.
3(b) Types of Sensors Based on Function
Sensors are classified as imaging sensors and non-imaging sensors. Imaging sensors capture images, while non-imaging sensors measure properties like temperature or radiation intensity without producing images.
4(a) Primary Absorbents of EM Energy in the Atmosphere
Major atmospheric absorbents include ozone, water vapor, carbon dioxide, and oxygen. These gases create absorption bands that influence satellite data quality.
4(b) Photogrammetry Numerical (Photograph Requirement)
The number of photographs required depends on ground coverage, scale, overlap, and format size. Using given data, ground coverage per photo is calculated first, followed by adjustment for overlaps to estimate total photographs needed. (Step-by-step solution expected in exam)
