basic concept of photograph, image and sensors for imaging and photography

Types of Photograph on Geographical Phenomena

Distinction Between Photographs and Images

1. Photographs:

   • Derived from Greek words:
     • Photos meaning "light."
     • Graphein meaning "to draw."
   • Photographs are images recorded on photographic film or camera storage chips.
   • Typically captured within the 0.3 µm to 0.9 µm range of visible and reflected infrared wavelengths.
   • Represent specific objects or features in pictorial form.
   • Used in various fields such as:
     • Science
     • Manufacturing
     • Film and video production
     • Business and communication

2. Images:

   • A broad term referring to any pictorial representation of an object or feature.
   • Classified based on the wavelength of electromagnetic radiation they represent.
   • Examples include:
     • X-ray images
     • Infrared images
     • Radar images
     • Photographs

Relationship Between Photographs and Images

1. All photographs are images, but not all images are photographs.
2. Photographs are a specific type of image that represent objects within the visible and reflected infrared wavelengths.
3. Images may represent objects using various parts of the electromagnetic spectrum.

Role of Sensors in Photography and Imaging

1. Cameras as Sensors:

   • Cameras detect specific wavelengths of the electromagnetic spectrum, primarily the visible spectrum, and produce photographs.
   • Examples include traditional cameras and digital cameras.
   

   Photograph

2. Other Sensors:

   • Not all sensors are cameras. Some detect other parts of the spectrum, such as:

     • X-ray sensors: Produce X-ray images.

       

       X-Ray

     • Infrared sensors: Produce infrared images.

       

       Infrared image

     • Radar sensors: Produce radar images.

All cameras are sensors, but not all sensors function as cameras.

Types of Photograph

Photographs can be grouped into:

1. Ground photographs
2. Aerial photographs
3. Satellite images photographs

Ground Photographs

As the name suggests, are camera pictures taken horizontally or obliquely from the ground level. They record objects with a camera carried by a person or vehicle which is on the ground. Photographs under this category give a horizontal view of the object recorded.

Types of Ground Photographs

Ground photographs can be grouped into the following categories:

1. Ground horizontal photograph
2. Ground close-up photograph
3. ground oblique photograph

Ground Horizontal Photograph

1. These are taken from ground level with the camera axis placed horizontally toward the object.
2. They provide a horizontal perspective, clearly showing the side or front view of objects.
3. Common characteristics include:
   • A clear representation of the object from a frontal or side perspective.

Ground Close-Up Photograph

1. Also referred to as ground view photographs, these are taken close to the object.
2. Characteristics:
   • Objects in the foreground appear large.
   • Progressive reduction in object size from foreground to background.
   • May include a small horizon in the background.
   • Divided into three parts: foreground, middle ground, and background.
3. Ground close-up photographs are detailed but do not show the top view of objects.

Ground Oblique Photograph

1. Captured from elevated positions such as rooftops, hills, or mountains, with the camera tilted at an angle between 30° and 60°.
2. Characteristics:
   • Objects decrease in size from foreground to background.
   • The amount of visible horizon depends on the tilt angle of the camera.
   • Photographs taken at acute angles above 50° show more of the object's top.

Advantages of Ground Oblique Photographs

1. Provide timely and location-specific landscape data.
2. Supplement data not captured by advanced geotechnologies, such as:
   • The intensity and extent of flooding.
   • Effects of locust invasions in a specific area.
3. Aid in field sketching due to clear and large features.
4. Represent more features compared to ground close-up photographs.
5. Offer valuable information for land-use planning.
6. Clearly display the relief of landscapes.
7. Useful for producing small sketch maps.

Disadvantages of Ground Oblique Photographs

1. Tend to distort uniformity due to scale reduction from foreground to background.
2. Difficult to determine the scale unless object size is known.
3. Unsuitable for large-area map production.
4. The horizon may not be clearly visible.
5. Limited generalization, as the area covered may not represent the whole study area.

Ground Photography Analysis

To analyze ground photographs effectively, follow these steps:

1. Identify the parts, sections, or positions of the photograph (foreground, middle ground, and background) and note the important features.
2. Read the caption and observe the position of features to create a simple sketch map of the area.
   • If objects decrease in size from left to right, the photographer was on the left side.
   • If objects decrease in size from right to left, the photographer was on the right side.
   • If objects decrease in size from foreground to background, the photographer was in front of the objects.
3. Lay a piece of tracing paper over the photograph and draw a trace diagram highlighting important features.
4. Write short descriptions of the features shown in the photograph.
5. Describe the processes responsible for forming the landforms and landscapes visible in the photograph.

Aerial Photographs

Aerial photographs are a type of photograph taken from above. It is important to distinguish between 'aerial photography' and 'aerial photograph'—the latter being the final product of the aerial photography process. Since its invention in the 1830s, aerial photography has become one of the most effective tools for map making, boundary location, road alignment determination, vegetation delineation, and many other activities.

Aerial photographs are captured by sensors mounted on flying objects such as kites, helicopters, drones, or airplanes. Though helicopters and airplanes were previously the primary tools for aerial photography, drones have recently surpassed them in usage due to their accessibility and efficiency.

Classification of Aerial Photography

Aerial photographs can be categorized based on the following criteria:

1. Camera Orientation: This refers to the axis of the camera, with common types being vertical and oblique photographs.
2. Angular Coverage: Different photographs provide varying levels of area coverage.
3. Emulsion Type: This includes different types of photographs like panchromatic black and white, color, infrared, and false-color composite photographs.

In this section, we will focus on types of aerial photographs based on camera orientation.

Types of Aerial Photographs

1. Vertical aerial photographs
2. Oblique aerial photographs

Vertical Aerial Photograph

1. Vertical aerial photographs, also known as terrestrial photographs, are taken with the camera axis positioned perfectly or nearly vertically.
2. The main characteristic of vertical aerial photographs is that they show only the top view of objects, rather than the side view.
3. These photographs are capable of covering relatively large areas compared to other ground photographs.
4. The scale of these photographs is almost uniform, particularly at the center. However, the scale decreases as you move away from the center of the captured area.
5. The central point of a vertical aerial photograph is known as the principal point.

Oblique Aerial Photograph

1. Oblique aerial photographs are taken at an angle of less than 90° with respect to the horizon.

2. These photographs are captured from a flying object whose camera axis is directed between the vertical axis and the horizontal plane.

3. Oblique aerial photographs can be further divided into:

   • Low Oblique Aerial Photographs: These do not show the horizon.

     

   • High Oblique Aerial Photographs: These show the horizon.

     

4. Oblique aerial photographs provide a wide, panoramic view of a large area and are useful for supplementing information from ground photographs.

5. They can cover a larger area than ground photographs and offer a clear picture of the landscape's relief.

6. The scale of these photographs is medium and tends to be less uniform compared to vertical photographs.

7. High oblique aerial photographs are particularly useful for tracking moving objects like vehicles, ships, trains, and landslides. They are also important for infrastructure planning, such as roads, railways, and buildings, as well as in land use planning.

How different types of aerial photographs are taken

Advantages of Vertical Aerial Photographs Over Maps

1. Aerial photographs provide detailed images of areas that were previously inaccessible, such as dense tropical forests, desert interiors, and swamplands.
2. They serve as crucial tools for environmental management, allowing for predictions of future conditions and the formulation of strategies to address these challenges.
3. Aerial photographs are valuable raw materials for land use planning, enabling the creation of settlement plans, infrastructure layouts, disaster management strategies, and the development of various projects and programs.
4. They are used extensively in land and hydrographic surveys and are essential sources of information for multiple purposes.
5. Aerial photographs are also used for tracking terrestrial and aerial moving objects, helping in traffic management and theft prevention.

Disadvantages of Vertical Aerial Photographs

1. Cost: Aerial photographs, especially those taken by commercial firms, can be expensive to produce, which may limit their availability for local land use planning.
2. Weather Impediments: Natural weather phenomena such as heavy rain, clouds, fog, and mist can hinder the acquisition of aerial photographs, delaying their availability.
3. Technological Alternatives: With the advent of Geographic Information Systems (GIS) and free online geographic data sources like Google Earth, the production of aerial photographs has declined.

Techniques for Interpreting Vertical Aerial Photographs

1. Tone, Colour, or Shade: This technique involves examining the darkness or brightness of objects. For example, forests, large water bodies, and oceans appear dark due to low reflectivity, while deserts and sandy areas appear bright because of high reflectivity.
2. Shape: Identifies objects based on their shape. For example, rivers and roads are typically curved, while stadiums and circular tanks are round in shape.
3. Texture: Refers to the roughness or smoothness of an object. Forests and residential areas tend to have a rough texture, while water bodies, grasslands, and snow appear smooth.
4. Pattern: Describes the arrangement of objects. Urban settlements and planted vegetation usually follow a regular pattern, while natural forests and mountainous regions follow irregular patterns.
5. Size: If the scale of the photograph is known, objects of known size (such as football fields) can be identified based on their size.
6. Site: Identifies features based on the environment in which they are found. For example, a bridge crossing a river or mangroves along a coastal area can be identified.
7. Association: Identifies features based on their association with other features. For example, a building with a chimney may indicate an industrial area, while a forest with wild animals might suggest a national park.
8. Shadow: Shadows help provide depth to aerial photographs. They can be used to distinguish the height of buildings or the presence of trees and can also estimate the time the photograph was taken based on the direction of the shadow.
9. Background Information: If other techniques fail, the interpreter can refer to maps and written descriptions of the area to identify objects and features.

The Concept of Satellites and Images

Satellites are man-made carriers designed to hold sensors, functioning similarly to human hands or camera stands. These platforms are not sensors themselves but provide support for the sensors that collect data. Satellites are launched by various nations and companies for different purposes, and they carry sensors—including cameras—that collect images for diverse applications. Some satellite sensors produce photograph-like images, while others provide reflective and emission signatures of the Earth's resources and conditions.

Each object on Earth has a unique reflection or emission signature, meaning that the reflective properties of vegetation, water, soil, and human bodies differ. This diversity allows satellites to generate images that require different techniques and skills for reading and interpretation.

Satellite Images or Imageries

Satellites are placed in specific paths, known as orbits, to capture data. There are three main types of satellite orbits:

1. Sun-Synchronous Satellites (Placed at about 500 km - 900 km): These satellites are generally used for remote sensing studies and can capture data over time in a way that accounts for the Earth's movement around the sun.
2. Geostationary Satellites (Placed at about 36,000 km): Also referred to as geosynchronous satellites, these are used for meteorological monitoring and telecommunication purposes. They maintain a fixed position relative to the Earth's surface.
3. Low Earth Orbit (LEO) Satellites: These satellites are typically used for activities like surveillance or spying, as they orbit much closer to the Earth.

Satellites detect and capture a wide range of data across various wavelengths, including visible, near-infrared, and mid-infrared. This data is then used to generate satellite images or photographs.

Remote Sensing and Satellite Imagery

Remote sensing is the process by which information is acquired from a recording device that is not in physical contact with the object being studied. Satellite sensors, through remote sensing, capture images in various wavelengths that can be interpreted for various applications. These satellite images provide crucial data for a wide range of sectors, including:

1. Meteorology: Understanding weather patterns and atmospheric conditions.
2. Oceanography: Monitoring the oceans, including temperature, currents, and pollution levels.
3. Biodiversity Conservation: Tracking species and ecosystems for conservation efforts.
4. Forestry: Monitoring forest health, deforestation, and land use changes.
5. Regional Planning: Providing data for urban and rural planning, infrastructure development, and land management.

Satellite images play a key role in decision-making processes related to land use planning, management, and mapping. They are also instrumental in scientific studies and monitoring environmental changes.

Imaging Systems

Satellite sensors capture a wide range of image data, and these images are categorized based on their imaging systems. The summary of these systems can be found in Table 5.1, which categorizes imaging systems used for various applications like meteorology, oceanography, forestry, and more.

Types of imaging systems

Imaging System	Example	Sensor	Platform
Filming	Aerial photographs	Camera film	Aircraft
Scanning	Meteorological satellite	Advanced Very High Resolution Radiometer (AVHRR)	Satellite
Scanning	Earth Observation Satellite (Landsat)	Multi-Spectral Scanner (MSS)	Satellite

Contribution of Satellite Images to Geographers and the Community

Satellite imagery and services play a crucial role in everyday life. They support various systems and technologies, including:

1. Mobile phone operations
2. Radio stations and television broadcasts
3. Vehicle and person tracking
4. Navigation systems

Satellites provide essential meteorological data, which include information on:

1. Cloud cover
2. Rainfall
3. Hurricanes
4. Ocean tides

This data is vital for:

1. Meteorological broadcasts
2. Disaster prediction and control

Additionally, satellite imagery offers valuable information regarding natural events, such as:

1. Wildfires
2. Volcanoes
3. Hurricanes
4. Torrential rainfalls

These insights help to minimize negative impacts on people. Satellite imagery's ability to produce extensive images has proven beneficial to various sectors, including:

1. Land use planners
2. Map makers
3. Oceanographers
4. Agriculturalists

Moreover, satellite data is instrumental in updating existing maps.

Difference between aerial photographs and the satellite images.

Satellite Image	Aerial Photograph
Covers a large area (approximately 185 x 185 km²) due to higher altitude.	Covers a small area (approximately 23 x 23 km²).
Multi-band aspect: records different objects in various colors (visible & invisible parts of the electromagnetic spectrum).	Records only in the visible light spectrum, relying on sunlight to produce photographs.
Difficult to interpret due to low spatial and high spectral resolution (wide range of electromagnetic spectrum).	Easy to interpret due to high spatial resolution and small range of features.
Can be taken throughout the year, making it easy to record and detect seasonal changes with multiple images captured over a few days.	Impossible to have repetitive coverage of the whole world.
Shows fewer details due to a small scale, resulting in low resolution.	Shows more details due to a large scale, resulting in high resolution.