Location on an Aerial Photograph (Leaving Cert Geography): Revision Notes
Location on an Aerial Photograph
Understanding the nine-section system
Aerial photographs can be systematically analysed by dividing them into nine equal sections. This grid system provides a standardised way to describe where features appear within any aerial photograph, making it easier to locate and identify specific elements.
The method you use to describe these nine sections depends on the type of aerial photograph you're examining.
This nine-section grid system is universally applicable to all aerial photographs, regardless of size or scale, making it an essential tool for geographical analysis.
Vertical photographs
Vertical photographs are taken with the camera pointing straight down towards the ground. These images provide a bird's-eye view of the landscape below.
Vertical photograph - An aerial image captured with the camera facing directly downwards, creating a view similar to looking at a map from above.
Using compass directions
For vertical photographs, you can use compass points to identify the location of features. The process works as follows:
- A north arrow helps you orientate the photograph correctly
- Once orientated, you can divide the image into nine sections using compass directions
- The sections are: North-west, North, North-east, West, Centre, East, South-west, South, South-east
This system only works when you know which direction the camera was facing when the photograph was taken. When the camera isn't facing north, the compass directions need to be adjusted accordingly.
Oblique photographs
Oblique photographs are taken at an angle rather than straight down. This creates a more natural perspective similar to what you might see from a tall building or hillside.
Oblique photograph - An aerial image taken at an angle to the ground, showing features from a slanted perspective rather than directly from above.
The foreground-background system
For oblique photographs, compass directions cannot be used effectively. Instead, you locate features using a different nine-section system:
Horizontal divisions:
- Left
- Centre
- Right
Vertical divisions:
- Background (furthest from camera)
- Middle ground (middle distance)
- Foreground (closest to camera)
This creates nine sections: Left Background, Centre Background, Right Background, Left Middle Ground, Centre Middle Ground, Right Middle Ground, Left Foreground, Centre Foreground, Right Foreground.
Determining the time of year
Aerial photographs contain numerous clues that help you identify when they were taken. By examining natural and human activities, you can determine the season:
Seasonal indicators
Worked Example: Identifying Summer Photographs
Key summer indicators to look for:
- Deciduous trees in full leaf - indicating active growing season
- Yellow freshly cut hay fields - summer harvest activity
- Shorter shadows - due to higher sun position
- Hay bales scattered across fields - post-harvest evidence
Spring:
- Ploughed fields are clearly visible
- Young animals can be spotted in fields
- Trees are beginning to show new growth
Summer:
- Deciduous trees are in full leaf
- Freshly cut hay fields appear yellow
- Hay bales are scattered across fields
- Shadows appear shorter due to the higher sun position
Autumn:
- Trees display brown, yellow and red foliage
- Shadows become noticeably longer
- Fewer animals are visible in fields
- Smoke begins to rise from house chimneys as heating systems are used
Winter:
- Trees appear bare without leaves
- Smoke consistently rises from chimneys
- Agricultural fields are left bare after harvest
- Longer shadows indicate the lower sun position
During summer months, the sun sits higher in the sky, creating more direct lighting and consequently shorter shadows on the ground.
Finding the camera direction
Determining which direction the camera was pointing when a photograph was taken can initially seem challenging, but there's a systematic approach:
Step-by-step method
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Identify distinctive features: Select a prominent feature in the foreground (front) of the photograph, such as a church, bridge, or distinctive building
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Find a background feature: Choose another distinctive feature in the background (rear) of the photograph
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Draw a connecting line: Visualise or draw a straight line connecting these two features - this represents the direction the camera was pointing
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Use an OS map: Locate the same two features on an Ordnance Survey map
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Apply the north arrow: Draw the same connecting line on the OS map and use the north arrow to determine the compass direction
This method provides an accurate way to calculate the camera's pointing direction, which is essential for properly orientating vertical photographs and understanding the geographical context of the image.
Key Points to Remember:
- Aerial photographs are divided into nine sections to help locate features systematically
- Vertical photographs use compass directions when the camera orientation is known
- Oblique photographs use foreground/middle ground/background combined with left/centre/right divisions
- Seasonal clues like leaf colour, shadow length, and field conditions reveal when photographs were taken
- Camera direction can be determined by connecting distinctive features visible in both the photograph and on an OS map