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4. Photogrammetry Surveying

Photogrammetry is defined as the art, science, and technology of obtaining reliable information about physical objects and their environment through photographic images. The chapter covers historical developments, types of aerial photographs, applications, advantages, disadvantages, and technical terms essential to the field. It emphasizes the importance of photogrammetry in mapping and modeling, utilizing both traditional and modern techniques involving digital photography and LiDAR.

Sections

Photogrammetry Surveying

This section explores photogrammetry surveying, including its techniques, types of photographs, and applications in various fields.

4 Section Overview

Start current section content and materials

4.1 Introduction

This section introduces photogrammetry, defining it as the technology for obtaining precise information from photographic images, particularly in mapping and understanding the Earth's surface.

4.2 Historical Developments

This section covers the historical milestones of photogrammetry, from its origin with early experiments in photography to the advancements in digital photogrammetry.

4.3 Types of Aerial Photographs

The section outlines the main types of aerial photographs used in photogrammetry, including vertical and tilted photographs, and terrestrial or close-range photographs.

4.3.1 Aerial photographs

This section covers the types of aerial photographs, their classifications, and applications in photogrammetry.

4.3.1.1 Vertical aerial photographs

This section covers the characteristics and importance of vertical aerial photographs in photogrammetry, explaining their role in mapping and data collection.

4.3.1.2 Tilted photographs

Tilted photographs are aerial images captured with the camera axis deviating from the vertical, offering unique perspectives and applications in photogrammetry.

4.3.1.2.1 Low oblique photographs

This section details low oblique photographs used in aerial photogrammetry, discussing their characteristics, applications, and significance.

4.3.1.2.2 High oblique photographs

This section defines high oblique photographs in photogrammetry, emphasizing their significance and applications.

4.3.2 Terrestrial or Close-range photographs

This section details terrestrial or close-range photographs, emphasizing their application in capturing detailed data for mapping and analysis.

4.4 Applications of Photogrammetry

Photogrammetry is widely applied in mapping, geology, forestry, agriculture, and various other fields for data collection and visual representation.

4.5 Advantages and Disadvantages of Photogrammetry

Photogrammetry offers numerous advantages for data collection, but it also has certain disadvantages that must be considered.

4.5.1 Advantages

This section outlines the various advantages of photogrammetry, emphasizing its cost-effectiveness and efficiency in data collection compared to traditional surveying methods.

4.5.2 Disadvantages

This section outlines the disadvantages associated with photogrammetry, highlighting the challenges in processing, accuracy, and environmental factors.

4.6 Comparison of Aerial Photograph with Map

This section discusses the differences between aerial photographs and maps, highlighting the geometric characteristics and applications of each.

4.7 Flight Planning

Flight planning is essential for the successful acquisition of aerial photographs, involving careful consideration of numerous factors including scale, flight lines, and weather conditions.

4.8 Technical Terms in Aerial Photogrammetry

This section outlines key technical terms used in aerial photogrammetry, enhancing the understanding of the discipline.

4.8.1 Exposure Station

The exposure station refers to the specific location of an aircraft during aerial photography, which is crucial for photogrammetric measurements.

4.8.2 Air-base or Camera base

This section describes the concept of air-base or camera base in aerial photogrammetry, detailing its significance in flight planning and photographic coverage.

4.8.3 Perspective centre

The perspective centre in aerial photogrammetry is crucial for understanding how photographs represent three-dimensional objects on a two-dimensional plane.

4.8.4 Perspective (Central) projection

Perspective projection forms the basis of aerial photographs, where the projecting rays from the camera lens pass through a single perspective center, impacting how images are represented geometrically.

4.8.5 Flight line

This section discusses the concept of flight lines in aerial photogrammetry, detailing the necessary planning and technical considerations for capturing aerial photographs.

4.8.6 Flight Strip

The flight strip refers to the corridor covered by each flight line during aerial photography, critical for capturing accurate imagery of a specified area.

4.8.7 Strip of photographs

This section explores the concept of a strip of photographs in aerial photogrammetry, emphasizing its significance in capturing and analyzing geographic data.

4.8.8 Total number of photographs

This section explains how to determine the total number of photographs used in aerial photogrammetry based on flight lines and camera strips.

4.8.9 Flying height

Flying height is a critical parameter in aerial photogrammetry, determining the scale of photographs and influencing the details captured.

4.8.10 Plumb line

The plumb line is a critical concept in aerial photogrammetry that indicates the vertical direction of gravity from the exposure station.

4.8.11 Camera axis

The section discusses the concept of camera axis in aerial photogrammetry, focusing on its implications for image geometry and the types of photographs.

4.8.12 Focal length

This section discusses focal length in the context of photogrammetry, explaining its significance in determining the scale of photographs.

4.8.13 Ground nadir

The ground nadir refers to the vertical point on the ground directly underneath the perspective center of a camera during aerial photography.

4.8.14 Fiducial marks

Fiducial marks are critical reference points on aerial photographs used for measurement and orientation in photogrammetry.

4.8.15 Fiducial axes

The section discusses fiducial marks and fiducial axes in aerial photography, emphasizing their role in photogrammetry.

4.8.16 Principal point (PP)

This section describes the principal point (PP) in photogrammetry as a key element in analyzing aerial photographs, detailing its definition, location, and its importance in photographic measurements.

4.8.17 Conjugate principal point (CPP)

The Conjugate Principal Point (CPP) is essential in photogrammetry, defined as the transfer of the principal point from one photograph to the adjacent one along the flight line.

4.8.18 Photograph centre

The photograph centre is a fundamental concept in photogrammetry, marking the optical intersection point in aerial images, crucial for accurate measurements.

4.8.19 Photographic nadir

The concept of photographic nadir is crucial in understanding aerial photography and its applications in photogrammetry.

4.8.20 Overlap

This section introduces the concept of overlap in aerial photogrammetry, emphasizing its significance in ensuring accurate data collection and modeling.

4.8.21 Superlap

Superlap refers to the common overlap region between three successive aerial photographs, enhancing spatial data accuracy.

4.8.22 Mosaic

The section discusses the concept of a mosaic in photogrammetry, detailing how it involves the seamless joining of aerial photographs to analyze large areas effectively.

4.8.23 Stereo-pair

This section explores the concept of stereo-pairs in photogrammetry, highlighting their significance in generating 3D models and understanding parallax effects.

4.8.24 Stereo-model

The stereo-model technique utilizes overlapping aerial photographs to create three-dimensional representations of the topography, enhancing our understanding of spatial relationships in photogrammetry.

4.8.25 Parallax

The concept of parallax is crucial in photogrammetry as it involves the apparent displacement of objects viewed from different angles, which is essential for determining height and measurements in aerial photography.

4.8.26 Floating mark

The floating mark is a reference point used in photogrammetry to assist in measuring and examining 3-D models derived from stereo-pairs of photographs.

4.8.27 Scale

This section covers the determination of scale in aerial photographs and how it relates to the elevation of terrain points.

4.8.28 Photo-interpretation

This section introduces the concept of photo-interpretation, focusing on how to identify and analyze features in aerial photographs for practical applications.

4.8.29 Control points

The section on control points discusses their critical role in photogrammetry for achieving accurate spatial data representation and mapping.

4.8.30 Orthogonal projection

Orthogonal projection is a mapping technique that simplifies the representation of three-dimensional objects onto a two-dimensional plane by maintaining the geometric relationships between points.

4.8.31 Ortho-photos

This section discusses ortho-photos, their significance in photogrammetry, and how they are utilized as accurate mapping representations.

4.8.32 Angle of tilt

This section explains the angle of tilt in aerial photogrammetry, describing its significance, how it relates to tilted photographs, and its geometric implications.

4.8.33 Isocentre

The isocentre is a pivotal point in tilted photographs where the bisector of the angle of tilt intersects the principal plane and the photograph.

4.8.34 Principal line

This section discusses the definition and significance of the principal line in aerial photogrammetry.

4.8.35 Principal plane

The principal plane refers to crucial concepts related to aerial photogrammetry, encompassing definitions and relationships essential for understanding photogrammetric processes.

4.8.36 Azimuth

The azimuth is defined as the horizontal angle measured clockwise from a reference plane, typically the north meridian, to the principal plane of a photograph.

4.8.37 Swing

This section provides an overview of the concept of 'swing' in aerial photogrammetry, detailing its definition, significance, and related terms.

4.8.38 Tilt Displacement

Tilt displacement refers to the outward or inward movement of images in tilted photographs in relation to the isocenter.

4.9 Scale of a Vertical Photograph

This section explains the concept of scale in vertical photographs, detailing how it is calculated based on focal length and flying height above ground.

Learning Objectives

  • Photogrammetry is a discipline that combines various technologies for obtaining, measuring, and interpreting photographic images.

  • The chapter outlines critical technical terms and methods involved in aerial and terrestrial photogrammetry.

  • Applications of photogrammetry extend across multiple fields such as mapping, geospatial analysis, agriculture, and medicine.

Key Concepts

Photogrammetry

The art, science, and technology of obtaining reliable information about physical objects and the environment through processes of recording, measuring, and interpreting photographic images.

Vertical Aerial Photographs

Aerial photographs taken with the camera axis positioned vertically or nearly vertically, essential for accurate measurements.

Tilted Photographs

Aerial photographs taken with the camera tilted more than 3° from the vertical, which may be classified into low and high oblique photographs.

Digital Photogrammetry

The phase of photogrammetry where digital images are processed using computer software to produce outcomes like Digital Elevation Models.

LiDAR

Light Detection and Ranging, a technology that uses laser light to measure distances and create detailed three-dimensional models of the Earth's surface.

Practice Exercises

Total Questions

2

Estimated Time

4 min

Passing Score

70%

Instructions

  • Read each question carefully
  • You can use hints if you need help
  • Complete all questions before submitting
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