photograph interpretation

In the process of interpreting images, various skills are applied to analyze different aspects of the photograph. For instance, if you encounter a hygrophyte or xerophyte plant in a photo and need to describe it, you will often section the photograph to better understand and interpret the objects within it.

A photograph can be divided into three main sections:

1. Foreground: This section is closest to the camera, where features appear large and clear.
2. Middle Ground: The area in the middle distance from the camera. Objects in this section appear smaller than in the foreground but are still moderately clear.
3. Background: This is the farthest section from the camera, where features such as tall trees and horizons appear small and unclear.

Location of parts of photograph horizontally

When interpreting a photograph, it may sometimes be helpful to divide the image further into three equal vertical parts: left, center, and right. This division allows for a more precise description of the location of objects in the photograph.

1. Left: Refers to the part of the photograph located on the left side, which can be in the foreground, middle ground, or background.
2. Center: Refers to the central part of the photograph, where the object's position relative to others can be described more accurately.
3. Right: Refers to the part of the photograph located on the right side, again, which can be in the foreground, middle ground, or background.

Parts of a horizontal photograph commonly used in interpretation

Location of parts of a photograph commonly used in interpretation

1. Nature of the Camera to be Used The camera's focal lens, film used, and filtration capacity are crucial factors. A camera with a large focal lens and high filtration capacity (against cloud cover, dust, and fog) produces sharper and better photographs compared to one with a small focal lens.
2. Knowledge of the Photographer The competence of the photographer plays a significant role in producing a quality photograph. A well-trained photographer is capable of selecting an appropriate location and effectively using the camera to capture the best image.
3. Position of the Photographer The distance and height of the photographer relative to the objects being captured affect the quality of the photograph. Ground-level photographs are generally considered the best due to their optimal angle and clarity.
4. Nature of the Targeted Area The terrain of the area influences photograph quality. Levelled areas are ideal for capturing ground photographs, while slopes or mountainous regions can cause image distortion.
5. Weather Conditions A clear day free from clouds, fog, and extreme sunlight provides the best conditions for photography.
6. Time at Which the Photograph is Taken The best photographs are taken during the day, avoiding both night-time and the intense sunlight of noon.

The efficiency and accuracy of photo interpretation can be influenced by several factors related to the photograph and imaging sensors. The following limitations affect the quality and clarity of the photograph:

1. Weather Conditions Cloud cover, fog, and other weather phenomena can reduce the quality of the photograph, making interpretation difficult.
2. Sun Angle The angle of the sun at the time the photograph is taken affects the brightness or darkness of the photograph, which may influence interpretation.
3. Camera Lens Quality The size and quality of the camera lens impact the resolution and clarity of the photograph.
4. Paper Type and Printing Method The type of paper and the method used to print the photograph can affect the final image quality, influencing interpretation.
5. Season of the Year In the rainy season, vegetation is greener, causing the photograph to appear darker. Conversely, during the dry season, when vegetation is less green, the photograph appears brighter.
6. Position of the Camera The proximity of the camera to the object being photographed determines the clarity of the image. A camera closer to the object provides a clearer photograph.
7. Color of the Object Objects with dark colors, such as black, may not be as clear due to their dark tones, whereas bright-colored objects tend to be more visible and clear in photographs.

Apart from understanding the qualities and elements that aid in interpreting photographs, several skills are necessary for effective interpretation. These skills help in determining title, estimating time and season, identifying human activities, estimating feature sizes, suggesting the location of the scenery, and estimating direction.

Key Skills and Techniques in Photograph Interpretation:

1. Determination of the Title:
   • The title can be inferred from the photograph itself by analyzing the foreground, middle ground, and background.
   • Familiarity with the area depicted can also provide clues for suggesting a title.
2. Estimating Time of Day:
   • The time of day can be inferred by analyzing shadows cast by objects.
   • For instance:
     • Shadows are shortest at midday.
     • Shadows are longest early in the morning or late in the afternoon.
     • If shadows are on the right-hand side, it could indicate that the photograph was taken in the morning, and if on the left, it might have been taken in the evening.
3. Determining the Hemisphere and Direction:
   • The hemisphere can be estimated based on the behavior of shadows and sun position.
   • Beyond the tropics, the sun never gets overhead, and shadows behave similarly, being shortest at midday and pointing poleward.
4. Identifying the Season:
   • Bright, clear skies with dry vegetation can indicate a dry season.
   • Luxuriant vegetation, young crops, flowering plants, and cloud presence may indicate a rainy season.
   • Snow on the ground can signal winter.
5. Identifying Weather Conditions:
   • The weather can be inferred from physical features, human activities, and the nature of the sky in the photograph.
   • Presence or absence of clouds can indicate weather conditions at the time of the photograph.
   • The types of clothes worn by individuals and the activities shown can also offer clues about the weather.
6. Estimating Sizes of Features:
   • Estimating the size of features can be challenging due to scale distortion in photographs, where objects appear smaller as they move toward the background.
   • A familiar object, like a coin or pen, can be used to estimate the size of other objects in the photograph.
7. Inferring Climatic Conditions:
   • Climate can be inferred by observing physical features and human activities.
   • Types of houses, crops, and animals can help determine the climatic conditions:
     • Short houses with mud roofs in rural areas may indicate semi-arid conditions.
     • The presence of sugarcane plantations suggests a warm climate, while tea and coffee plantations indicate a cooler climate with reliable rainfall.
     • Drought-resistant crops like sisal suggest low rainfall.
8. Observing Natural Vegetation:
   • Dense forests with tall trees suggest an area receives heavy, reliable rainfall.
   • Bushes and grasslands indicate dominance of low and unreliable rainfall.

Table for interpretation of climatic type from the photograph

Several human activities can be identified or need to be identified in a photograph. These activities include:

1. Agriculture
   1. subsistence crop farming
   2. commercial crop farming
   3. livestock farming
   4. plantation farming
2. tourism
3. trade
4. fishing
5. lumbering
6. industrial manufacturing
7. mining

Agriculture or Farming

Subsistence Crop Farming:

1. Characterized by several features such as permanent and temporary houses.
2. Land segmented into small portions, and fields separated by hedges, sisal, or planted trees.
3. Use of rudimentary tools such as hand hoes and machetes.

Commercial Crop Farming:

1. Characterized by the presence of cash crops such as tea, coffee, and sisal.
2. Presence of modern machinery and processing factories.
3. Feeder routes within the farm and facilities for collecting produced goods.
4. Large farm size.

Livestock Farming:

1. Traditional Livestock Keeping: Characterized by cattle grazing in natural grasslands, especially in semi-arid areas. Traditional breeds such as Zebu cattle are commonly kept.
2. Ranching: Evidence includes large fields divided into paddocks, cow sheds near farmhouses, windmills, and water supplies (e.g., water tanks, ponds, water holes, or reservoirs).
3. Dairying: High-grade cows with big udders, milk processing plants, and zero grazing units are common indicators.

Plantation Farming:

1. Evidence includes a single crop covering large areas (e.g., sugarcane, tea, sisal, wheat).
2. Storage facilities near the farm and a large number of laborers in the fields (e.g., picking tea or coffee).
3. Nucleated settlements within the farm meant for workers.

Scale of Production:

1. Small Scale Production: Characterized by food crop cultivation, use of local tools (hand hoes, axes, machetes), family labor, and small farm size.
2. Large Scale Production: Characterized by cash crop production, use of modern machinery (e.g., harvesters), large and well-mechanized farms.

Tourism

Indicated by large water bodies, forests, wild animals, hills, coasts, caves, historical sites, or mountains.

Trade

Evidence is found in towns and shopping malls.

Fishing

Indicated by the presence of boats, large water bodies (e.g., oceans, rivers, lakes, dams), and net drying yards.

Lumbering

Evidenced by the presence of forests, sawmills, chainsaws, and timber/logs.

Industrial Manufacturing

Indicated by industries, ginnery, or large plantations of crops like sisal, tea, or coffee that require processing industries within the farm.

Mining

Indicated by the presence of quarries.

The landscape is formed by several features, with common features typically found on photographs including

1. relief
2. settlements
3. drainage.

Relief

Relief features are varied in nature and include the following:

Flat Landscape

1. Found in both lowlands and uplands.
2. Lowlands: Known as plains, typically less than 500 meters above mean sea level. These are often associated with meandering rivers.
3. Uplands: Above 500 meters, flat landscapes are called plateaus, which have steep sloping edges.
4. Flat areas can often be identified by the types of crops grown in the area. For example, sugarcane and rice are commonly grown on flat lands.
5. Irrigation systems also indicate relatively flat terrain.

Mountainous Landscape

1. Elevated landforms above 2000 meters are referred to as mountainous areas.
2. These are characterized by steep slopes on individual blocks of land or extended mountainous ranges.
3. Crops grown in mountainous areas can help deduce the altitude. For example, crops like pyrethrum, tea, wheat, and coffee are typically grown in highland regions.
4. In Tanzania, tea is grown in the Southern Highlands, in places such as Mufindi (Iringa) and Rungwe (Mbeya).

Settlements

Settlements can be classified into two major types: rural and urban.

Rural Settlements

1. Evidence of rural settlements includes simple architectural designs of semi-permanent houses.
2. The layout is unplanned, with uneven distribution of dwellings.
3. Farming or fishing activities may also be visible in rural settlements.

Urban Settlements

1. Urban settlements are indicated by permanent buildings, regular street patterns, and multi-storey buildings.
2. Industrial areas, including warehouses, may be present.
3. High population density is common, along with port facilities such as docks, cranes, and containers.
4. A well-developed communication network is also often visible.

Drainage

Drainage refers to the natural or artificial flow of water from an area through streams to rivers, and the movement of water from the land to lakes or oceans. Drainage features may include swamps, water holes, ponds, and reservoirs.

Key Features of Drainage in Photographs

1. Water Bodies:
   • Water features are easily recognizable in all types of photographs.
   • Deep waters in lakes and oceans typically appear darker, while shallow waters in rivers and continental shelves appear brighter.
2. Waterfalls and Rapids: The presence of waterfalls and rapids indicates that the river is flowing through a steep region or landscape.
3. River Meanders: River meanders suggest that the river is in its middle or old stages.
4. River Delta: A river delta is identified by the presence of many channels or distributaries before the river enters a lake or ocean.

Recognizing River Patterns in Aerial Photographs

1. In aerial photographs, various river patterns can be recognized, such as:
   • Dendritic (branch-like pattern)
   • Trellis (parallel pattern)
   • Radial (radiating pattern)

Photographic scale

The scale of a vertical aerial photograph is a function of the camera's focal length (f) and the altitude or height from which the exposure is made or of aircraft.

$S = \frac{f}{H}$

Where: f = Camera' focal length H = Flying height of the aircraft S = Scale

Notes on Aerial Photography

1. Formula for Scale Calculation: This formula is used when the photograph is taken on a flat surface.
2. Vertical Aerial Photographs:
   • These photographs provide a true record of angles.
   • Horizontal Distances:
     • Subject to wide variations due to:
       • The flying height of the aircraft.
       • The focal length of the aerial camera.
   • Flying Height: Measured from a specified elevation above mean sea level.
   • Focal Length:
     • Varies according to the specified need and purpose.
     • In Tanzania, commonly used focal lengths are:
       • f = 152 mm
       • f = 132 mm
3. Rough Surface Photography: If the photograph is taken on a rough surface, use the following formula to compute the scale:

$S = \frac{f}{H - h}$

Where: h = Average elevation of the photographed area.

New line scale average is applicable when the altitude of the aerial photographs is unknown or not given. In such cases scale may be determined as shown in the following example.

Example 1

A camera in an aircraft at an altitude of 3,300 m was used to take a photograph. Determine the focal length of the camera if the scale of the photograph is 1:25,000.

Solution

Formula:

$S = \frac{f}{H}$

Data given:

Height of the plane (H) = 3300 m Scale of photo (S) = 1:25,000 f = ?

$\frac{1}{25,000} = \frac{f}{3300 \text{ m}}$

$25,000 \times f = 3300 \text{ m} \times 1$

$25,000f = 3300 \times 1000 \text{ mm}$

$\frac{25,000f}{25,000} = \frac{3,300,000 \text{ mm}}{25,000}$

Therefore the focal length = 132 mm

Example 2

Calculate the flying height of an aircraft which produced a vertical aerial photograph at the scale of 1:20,000 whose mean ground height was 500 m above mean sea level with focal length of 152 mm.

Solution:

Formula:

$S = \frac{f}{H - h}$

Given data: h = 500 m f = 152 mm S = 1:20,000 H = ?

$\frac{1}{20,000} = \frac{152 \text{ mm}}{(H - 500) \times 1000 \text{ mm}}$

$20,000 \times 152 \text{ mm} = 1000 \text{ mm} \times H - 500,000 \text{ mm}$

$3,040,000 \text{ mm} = 1000 \text{ mm} \times H - 500,000 \text{ mm}$

$3,040,000 \text{ mm} + 500,000 \text{ mm} = 1000 \text{ mm} \times H$

$\frac{3,540,000 \text{ mm}}{1000 \text{ mm}} = \frac{1000 \text{ mm} \times H}{1000 \text{ mm}}$

$3540 \text{ m} = H$

Therefore, flying height of an aircraft is 3540 m