CBSE Class 11 Geography: Introduction to Aerial Photographs NCERT Solutions

Reviewed by NCERT Help Editorial Team · Updated on 29 Jul 2026

NCERT Solutions PDF Class 11 PDF

This chapter, "Introduction to Aerial Photographs," for CBSE Class 11 Geography, provides a foundational understanding of aerial photography. The NCERT Solutions cover the fundamental concepts, including the different types of aerial photographs based on the horizon's appearance and the coincidence of Nadir and principal points. It delves into the projection used in aerial photography and explains how these photographs are captured using aircraft and precision cameras. The solutions also highlight the significant advantages of aerial photographs over ground-based observations, such as providing a bird's-eye view and capturing a moment in time with greater sensitivity than human eyes. Furthermore, the text touches upon the historical context of aerial photography in India and its crucial applications in topographical mapping and image interpretation, forming the basis of photogrammetry. The solutions also introduce methods for determining the scale of aerial photographs. These detailed explanations and step-by-step solutions are designed to aid students in grasping the core principles and preparing effectively for their examinations.

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Board	CBSE
Class	Class 11
Subject	Geography
Session	2026
Language	English
Type	NCERT Solutions
Chapter	6. Introduction to Aerial Photographs

Chapter summary

Chapter 6, "Introduction to Aerial Photographs," for Class 11 Geography NCERT Solutions, focuses on the basics of aerial photography. It explains the classification of aerial photographs (vertical, near-vertical, low-oblique, high-oblique), the projection systems used, and the process of capturing them. Key advantages over ground observation are discussed, alongside the historical development and applications in India. The solutions also cover the uses in topographical mapping and image interpretation, introducing photogrammetry and methods for scale determination. This chapter equips students with essential knowledge for understanding remote sensing data.

Learning outcomes

Understand the different types of aerial photographs and their characteristics.
Explain how aerial photographs are taken and their advantages over ground-based observation.
Identify the uses of aerial photographs in mapping and interpretation.
Describe the concept of photogrammetry and its relation to aerial photographs.
Recognize the historical context and applications of aerial photography in India.
Learn methods for determining the scale of aerial photographs.

Topics covered

Paper topics

Types of Aerial Photographs
Vertical Photographs
Oblique Photographs (Low and High)
Nadir and Principal Point
Projection in Aerial Photography
Advantages of Aerial Photography
Aerial Photography Process
Aerial Photography in India
Uses of Aerial Photographs
Topographical Mapping
Image Interpretation
Photogrammetry
Scale Determination

Important topics

Types of Aerial Photographs (Vertical vs. Oblique)
Advantages over Ground Observation
Uses in Mapping and Interpretation
Concept of Photogrammetry
Methods of Scale Determination

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Questions and Solutions

Multiple Choice Questions

1. In which of the following aerial photographs does the horizon appear?

Vertical
Near-vertical
Low-oblique
High-oblique

Solution: The horizon is visible in high-oblique aerial photographs. These photographs are taken with the camera tilted at a significant angle, allowing a wide view that includes the horizon. Vertical and near-vertical photographs are taken looking straight down, while low-oblique photographs are taken at a lesser tilt where the horizon is typically not visible.

2. In which of the following aerial photographs do the Nadir and the principal points coincide?

Vertical
Near-vertical
Low-oblique
High-oblique

Solution: The Nadir and the principal points coincide in a vertical aerial photograph. The principal point is the center of the photograph, and the Nadir is the point directly below the camera lens on the ground. When the camera is perfectly vertical, these two points are the same.

3. Which type of projection is used in aerial photographs?

Parallel
Orthogonal
Central
None of the above.

Solution: Aerial photographs utilize a central projection. In this type of projection, all points on the ground are projected towards a single point, which is the perspective center (the camera lens), onto the plane of the photograph. This is fundamentally different from parallel or orthogonal projections.

Short Questions

4. State any three advantages that an aerial photograph offers over ground-based observation.

Solution: Aerial photographs offer several advantages over ground-based observations:

Comprehensive View: They provide a bird's-eye view, allowing observation of large areas and their spatial relationships simultaneously, which is impossible from ground level.
Instantaneous Record: An aerial photograph captures the surface features at a precise moment in time, serving as a permanent and objective record of conditions at that instant.
Enhanced Sensitivity: The photographic film used can record details and subtle variations in light and tone that may be beyond the sensitivity of the human eye, revealing features not easily seen from the ground.

5. How is an aerial photograph taken?

Solution: An aerial photograph is taken from an aircraft, such as an airplane or helicopter, equipped with a specialized, high-precision camera. The camera is mounted to capture images of the Earth's surface as the aircraft flies over it. The process involves careful planning of flight paths and altitudes to ensure complete and systematic coverage of the area of interest.

6. Present a concise account of aerial photography in India.

Solution: Aerial photography has a significant history in India, dating back to 1920 with large-scale aerial photographs of Agra city. Subsequently, the Survey of India conducted aerial surveys of forest areas, such as the Irrawaddy Delta, in the early 1920s. Today, the Directorate of Air Survey in New Delhi oversees aerial photography for the entire country. The government officially authorizes three agencies for this task: the Indian Air Force, the Air Survey Company in Kolkata, and the National Remote Sensing Agency in Hyderabad, which collectively cover different parts of India.

7. Answer the following questions in about 125 words:

i) What are the two major uses of an aerial photograph? Elaborate.

Solution: The two major uses of aerial photographs are topographical mapping and image interpretation. Topographical mapping involves using aerial photographs to create detailed maps that show the physical features of the Earth's surface, including elevation, landforms, and water bodies. This process is a core part of photogrammetry, which is the science of making measurements from photographs. Image interpretation is the art of identifying objects in aerial photographs and assessing their significance. A trained interpreter can analyze these photographs to understand various aspects of the landscape, such as land use patterns, geological formations, soil types, vegetation cover, and urban development.

ii) What are the different methods of scale determination?

Solution: There are primarily three methods for determining the scale of an aerial photograph: Method 1: By Establishing Relationship between Photo Distance and Ground Distance

If the actual ground distances between two identifiable points are known, the scale (Sp) of the aerial photograph can be calculated using the formula:

$Sp = \frac{\text{Photo Distance (Dp)}} {\text{Ground Distance (Dg)}}$

Here, Dp is the distance measured between two points on the aerial photograph, and Dg is the corresponding distance between the same two points on the ground. Method 2: By Establishing Relationship between Photo Distance and Map Distance

This method involves comparing the distance measured on the aerial photograph with the corresponding distance on a map of the same area, provided the map's scale is known. The scale of the photograph can be derived by relating the photo distance to the map distance and then using the map's scale factor.

(Note: The source document only provided details for two methods. A third method, often involving focal length and flying height, is typically discussed in this context but was not present in the provided text.)

Common mistakes

Confusing the characteristics of different types of aerial photographs (e.g., horizon appearance).
Not clearly distinguishing between the uses of aerial photographs for mapping versus interpretation.
Difficulty in understanding the principles of scale determination from photographs.
Overlooking the advantages aerial photographs offer compared to direct observation.

Revision tips

Memorize the key differences between vertical, near-vertical, low-oblique, and high-oblique photographs.
Focus on understanding the practical applications of aerial photography in fields like mapping and land use analysis.
Practice the methods for determining the scale of an aerial photograph.
Review the advantages of aerial photography to articulate them clearly.
Understand the definition and importance of photogrammetry.

Practice MCQs

Q1. In which type of aerial photograph does the horizon become visible?

Q2. When do the Nadir and the principal point coincide in an aerial photograph?

Q3. What type of projection is fundamentally used in the creation of aerial photographs?

Q4. Which of the following is a significant advantage of aerial photographs over ground-based observation?

Q5. Photogrammetry is best described as:

Frequently asked questions

What is the main difference between vertical and oblique aerial photographs?

In vertical aerial photographs, the camera points directly downwards, so the Nadir and principal point coincide. In oblique photographs, the camera is tilted, and the horizon may be visible in high-oblique shots.

Why are aerial photographs considered advantageous over ground-based observations?

Aerial photographs provide a bird's-eye view of large areas, capture a detailed record of surface features at a specific instant, and utilize film sensitive to a wider range of light than human eyes.

What is photogrammetry and how does it relate to aerial photographs?

Photogrammetry is the science of making measurements from photographs. Aerial photographs are the primary data source for photogrammetry, enabling measurements of length, breadth, and height of objects on the ground.

What are the primary uses of aerial photographs mentioned in the chapter?

The two major uses are topographical mapping, which involves creating maps of the Earth's surface, and image interpretation, which involves analyzing the photographs to understand land use patterns, landforms, and other features.

How can the scale of an aerial photograph be determined?

The scale can be determined by establishing a relationship between photo distance and ground distance, or between photo distance and map distance, provided the necessary ground or map measurements are available.

What historical significance does aerial photography have in India?

Aerial photography in India began with large-scale photographs of Agra city in 1920, followed by surveys of forests. The Survey of India, under the Directorate of Air Survey, oversees aerial photography for the entire country.

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