CBSE Class 11 Geography: Chapter 6 - 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 provides a foundational understanding of aerial photographs within the context of Geography for Class 11 students following the CBSE curriculum. It delves into the fundamental concepts of aerial photography, explaining what it is and how it differs from ground-based observations. The solutions cover the various types of aerial photographs, including vertical, near-vertical, low-oblique, and high-oblique, and the specific characteristics of each, such as the appearance of the horizon and the coincidence of Nadir and principal points. Furthermore, the chapter explores the projection methods used in aerial photography and its significant applications in fields like topographical mapping and image interpretation. The solutions also detail the historical context of aerial photography in India and explain methods for determining the scale of aerial photographs. These NCERT Solutions are designed to help students grasp these key concepts thoroughly, aiding in their exam preparation and revision.

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Quick info

Board	CBSE
Class	Class 11
Subject	Practical Work in Geography
Session	2026
Language	English
Type	NCERT Solutions
Chapter	Chapter 6

Chapter summary

Chapter 6, 'Introduction to Aerial Photographs,' for CBSE Class 11 Geography, focuses on the basics of aerial photography. The NCERT Solutions cover the classification of aerial photographs based on their orientation (vertical, oblique), the principle of central projection used, and the advantages over ground-based views. It also touches upon the historical development and current practices of aerial photography in India and explains methods for scale determination. The solutions aim to provide clarity on these essential topics for students.

Learning outcomes

Understand the definition and purpose of aerial photographs.
Differentiate between various types of aerial photographs (vertical, oblique).
Explain the advantages of aerial photography over ground-based observations.
Describe the process of taking an aerial photograph.
Recognize the historical context of aerial photography in India.
Identify and explain methods for determining the scale of aerial photographs.

Topics covered

Paper topics

Introduction to Aerial Photographs
Types of Aerial Photographs
Vertical Photographs
Oblique Photographs (Low and High)
Advantages of Aerial Photography
Aerial Photography Process
Aerial Photography in India
Photogrammetry
Image Interpretation
Scale Determination Methods
Central Projection

Important topics

Types of Aerial Photographs and their characteristics
Advantages of Aerial Photography
Methods of Scale Determination
Photogrammetry and Image Interpretation
Historical Development of Aerial Photography in India

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Questions and Solutions

Multiple Choice Questions

1. In which of the following aerial photographs the horizon appears?

Vertical
Near-vertical
Low-oblique
High-oblique

Solution: The horizon is visible in aerial photographs taken at a significant angle from the vertical. Among the given options, high-oblique photographs are taken at a steep angle, allowing the horizon to be clearly seen. Low-oblique photographs are taken at a shallower angle and may not show the horizon, while vertical and near-vertical photographs are too close to nadir to capture the horizon. Therefore, the correct answer is high-oblique.

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

Vertical
Near-vertical
Low-oblique
High-oblique

Solution: The Nadir point is the point directly below the camera lens on the ground. The principal point is the center of the aerial photograph. In a perfectly vertical aerial photograph, the camera is aimed straight down, meaning the Nadir point and the principal point are at the same location. For near-vertical and oblique photographs, these points do not coincide due to the tilt of the camera.

3. Which type of the following projections is used in aerial photographs?

Parallel
Orthogonal
Central
None of the above.

Solution: Aerial photographs are created using a central projection. In this type of projection, all the light rays from the ground pass through a single point (the camera lens) before reaching the film or sensor. This is analogous to how a pinhole camera works. Parallel and orthogonal projections are used in other mapping contexts but not for the direct capture of aerial photographs.

Short Questions

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

Solution: Aerial photographs provide several significant advantages compared to observations made from the ground:

Comprehensive View: They offer a bird's-eye perspective, allowing for the observation of large geographical areas and their features simultaneously, which is impossible from ground level.
Instantaneous Record: An aerial photograph captures the state of the Earth's surface at a precise moment in time. This makes it a valuable historical document and allows for the study of dynamic processes.
Enhanced Detail and Sensitivity: The films used in aerial photography can be sensitive to a wider spectrum of light and can capture finer details than the human eye, revealing features not easily discernible from the ground.

5. How is an aerial photograph taken?

Solution: An aerial photograph is typically taken from an aircraft, such as an airplane or a helicopter, that is equipped with a specialized, high-precision camera. The camera is mounted in the aircraft and is oriented to capture images of the ground below. The process involves flying the aircraft over the area of interest at a specific altitude and speed, while the camera is triggered at regular intervals or specific points to acquire the photographs.

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

Solution: Aerial photography has a significant history in India. Early large-scale aerial photographs of Agra city were acquired as far back as 1920. Subsequently, the Survey of India undertook aerial surveys of forest areas, such as the Irrawaddy Delta forests between 1923 and 1924. Currently, comprehensive aerial surveys for the entire country are conducted under the supervision of the Directorate of Air Survey, New Delhi. The Indian government officially authorizes specific agencies for this task, including the Indian Air Force, the Air Survey Company in Kolkata, and the National Remote Sensing Agency in Hyderabad, to capture aerial photographs of various regions across India.

7. Answer the following questions in about 125 words:

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

Solution: Aerial photographs serve two primary purposes: topographical mapping and image interpretation. These distinct applications have driven the development of photogrammetry, which is the science of making precise measurements from photographs. Through photogrammetry, crucial data related to the length, breadth, and height of ground features can be accurately determined from the photographic images. Image interpretation, on the other hand, is the art of identifying objects and assessing their significance within the photograph. A skilled interpreter can analyze aerial photographs to understand land use patterns, identify topographical forms, classify soil types, and gather a wealth of information about the environment.

ii) What are the different methods of scale determination?

Solution: There are primarily three methods used to determine 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 on the photograph are known, the scale of the aerial photograph can be calculated using the formula:

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

Where Dp is the distance between two points measured on the aerial photograph, and Dg is the actual distance between the same two points on the ground.

Method 2: By Establishing Relationship between Photo Distance and Map Distance

This method involves comparing distances measured on the aerial photograph with corresponding distances on a map of the same area, provided the map's scale is known. The scale of the photograph is then determined by the ratio of the photo distance to the map distance, adjusted by the map's scale factor.

(Note: The source document only provided details for two methods. A third method, often involving camera focal length and flying height, is typically discussed in comprehensive texts on photogrammetry.)

Common mistakes

Confusing the characteristics of different types of oblique photographs.
Difficulty in understanding the concept of Nadir and principal points.
Errors in applying the formula for scale determination.
Not clearly distinguishing between image interpretation and topographical mapping.

Revision tips

Review the definitions and key features of vertical and oblique aerial photographs.
Practice identifying the advantages of aerial photography with real-world examples.
Understand the historical timeline of aerial photography in India.
Work through the scale determination methods to ensure accuracy.
Focus on the distinct uses of aerial photographs in mapping and interpretation.

Practice MCQs

Q1. In which type of aerial photograph does the horizon typically appear?

Q2. In which type of aerial photograph do the Nadir and the principal points coincide?

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

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

Q5. Photogrammetry is best described as:

Frequently asked questions

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

Vertical aerial photographs are taken with the camera pointing directly downwards, while oblique aerial photographs are taken at an angle, allowing the horizon to 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 record of features at a specific instant, and can record details beyond the sensitivity of human eyes.

What is photogrammetry?

Photogrammetry is the science of making measurements from photographs, used to determine lengths, breadths, and heights of objects depicted in the images.

How is the scale of an aerial photograph determined?

The scale can be determined by establishing the relationship between photo distance and ground distance, or between photo distance and map distance, using specific formulas.

When did aerial photography begin in India?

Large-scale aerial photographs of Agra city were obtained in 1920, and aerial surveys of forests were conducted as early as 1923–24.

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