Aerial photographs

Introduction

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

What are aerial photographs?

Aerial photographs (also known as vertical aerial photographs or vertical air photographs) are taken from a high point, which is directly above the centre of the area being photographed. This type of photograph allows people to see what an area looks like when they are looking straight down on it. Since the axis of the camera needs to be perpendicular to the surface of the Earth in vertical aerial photographs, they are usually taken using a camera mounted on the bottom of an aircraft. Aerial photographs are usually taken from aircraft flying up to six kilometres above the Earth's surface.

See image 1

Aerial photographs are of particular use to geographers and cartographers. When taken from a relatively low altitude, they are also used to plan towns and structures, accurately measure roads and rivers, survey the resources of an area, and show how the physical and cultural features of a place have changed over time.

Advantages and disadvantages

Aerial photographs have an advantage over ground level photographs. An aerial view enables the whole of an area to be observed, rather than just a portion of it. Aerial photographs are also sometimes favoured over oblique photographs. The reason for this is that the scale of aerial photographs is relatively consistent throughout the entire frame. This enables relatively accurate measurements to be made using photographs taken from this vertical view.

The main disadvantage of aerial photographs is that the point of view is unfamiliar. Most features look very different when viewed from above. This can make it difficult to recognise ground features.

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Recording and interpreting

There are two ways to record a photograph. It can be sketched or it can be described. (Refer to Topic 5, Chapter 5: Line drawings and sketch maps for more information on line drawings). When a person interprets information in a vertical photograph, the unfamiliar view means that it is not always easy to immediately identify all of the features. It is often easier to record observations by describing them in terms of their:

Shape

1. What basic geometric shape (square, circle, triangle etc.) does it resemble?
2. What sort of lines (long or short, straight or curved) does it comprise?

Size

1. Is it larger or smaller in size than the objects around it (or similar to it)?
2. According to the provided scale, how large is the object in the real world?

Shadow

1. What direction is the shadow facing? What position is the sun in?
2. What shape is the shadow? What could it be representing?
3. Is the shadow long or short? What time of day could this suggest?

See image 3

Tone (lightness or darkness)

1. Vegetation, especially in forests, usually has a dark tone.
2. The sandy shores of beaches usually appear light.
3. Roads can vary from being grey in tone (highways) to light (unsealed roads).

Associated features

1. A winding line, which is lined by trees, is most likely to be a river.
2. A group of small squares bunched together is likely to be a town.
3. A cluster of evenly spaced trees is most likely to be an orchard.

Once all of this information has been collected, students need to interpret it. Aerial photographs are particularly interesting to interpret because they show such a large area in a simple, map-like format. This enables students to not only interpret a large number of features but also interpret the patterns created. These patterns provide an insight into landuse, vegetation, transport, settlement and relief.