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Introduction

Oblique photographs are one type of photograph used by geographers. This chapter explains what an oblique photograph is and how it differs from other types of photographs. It discusses the advantages and disadvantages of an oblique photograph and outlines how to record and interpret oblique photographs.

Why use photographs?

Geographers use a wide variety of tools in their studies of environments and communities. These tools assist them to obtain and record more accurate results. In cases where recording data in a written format is too time consuming and not accurate, geographers often rely on a photograph to document the information. Photographs have a number of advantages. They can capture extraordinary detail which lasts forever and it takes less than a second to capture a single image. Photographs are relatively inexpensive to create and it is simple to compare two photographs from different periods in time or from different parts of the world.

What are oblique photographs?

Oblique photographs (also known as oblique aerial photographs or oblique air photographs) are taken from a high point, which is at an angle neither horizontal (ground level photograph) nor perpendicular (vertical aerial photograph) to the area being photographed. This angle is often referred to as a slope. Not long after the development of the camera in the 19th century, to achieve photographs from a sloping angle, oblique photographs began to be taken from cameras attached to balloons, kites and even carrier pigeons. With the advent of modern technology in more recent times, oblique photographs are now taken from an aeroplane or helicopter.

See images 1a and 1b

Oblique photographs are usually divided into two main types. A high oblique photograph features the horizon in the image. A low oblique photograph is directed at a lower angle, which means that the horizon is not visible.

The uses of oblique photographs are endless. Cartographers use them to construct physical and topographical maps. The property and construction industries also use oblique photographs to record and measure properties, as well as to track the progress of development sites.

Advantages and disadvantages

Oblique photographs have a number of advantages. They show more of an area than ground level photographs, since their view is not obscured by hills, trees or houses. Oblique photographs can also easily be assessed and understood. The perspective of an oblique photograph is similar to that of a conventional (ground-level) photograph, so the physical and cultural features of the landscape are still recognisable. This is unlike vertical aerial photographs which are presented from a map-like perspective.

Another advantage of oblique photographs is that they do not require the aircraft to fly directly overhead the area being photographed. This is particularly useful in the case of photo-reconnaissance by the military.

See images 2a and 2b 

A major disadvantage of an oblique photograph is that scale is inconsistent. This means that while distances can be calculated in the foreground, according to the provided scale, distances which are closer to the horizon would be completely inaccurate if calculated using the same scale.

See image 3

Recording and interpreting

While information can be recorded in a written format, a particularly useful way of recording the information in a photograph is by sketching it. The easiest way to begin a sketch is by tracing the general outline of the image. Once that is done, students should add the physical features, including trees and rivers, and the cultural features, such as houses and roads. It is important for students to also accurately label all of these features, so that the sketch can be referred to. (Refer: Topic 5, Chapter 5: Line drawings and sketch maps).

When interpreting a photograph, students need to infer (use factual knowledge to decide) what might be happening and the possible reasons for it. Some sample questions which students should attempt to answer include:

  • What is happening in the photograph?
  • What is the reason for this?
  • What are the consequences of this?
  • What do the features tell us about the people or place?
  • What is the most prominent part of the photograph and why?
  • Is it likely that this feature has changed over time? Why or why not?
  • How do these features affect one another?

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Question 1/5

1. Oblique photographs are able to see a large area, since their view is not obscured by trees and houses. This gives oblique photographs an advantage overů?

Ground level photographs

All of the above

Vertical aerial photographs

Satellite photographs

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