Aerial photography is a fascinating niche that the pros use for many different purposes, and there are many different types of aerial photography. The term aerial photography refers to taking photographs from an elevated position, often using an airborne craft, including such equipment as rockets, airplanes, hot air balloons, and more recently, drones.
To be considered an aerial photograph, you have to take the image with equipment that is not based on the ground. And, it is not the same as air-to-air photography where photographers are capturing images of other planes or airborne craft.
There are different kinds of aerial photography which experts categorize according to the camera axis (angle of the photo), the scale of the image (proximity and width of the area in the photograph), and the type of film. This photographic niche has a number of uses, but first let’s look at the various categories.
Categories of Aerial Photography
There are several different kinds of aerial images in each of the three main categories. The choice of a particular kind of aerial photography is typically based on the subject and purpose of the imagery.
There are three types of aerial images based on the orientation of the camera axis:
- Vertical photographs–the axis of the camera is in a vertical position. This results in little to no relief visible in the image and a smaller amount of area covered. Experts most often use vertical photographs like a map.
- Low oblique photographs–unlike with vertical photographs, to take low oblique photographs you tilt the camera axis more than 3 degrees in a manner that the horizon–the area where the earth and sky meet–is not visible in the image.
- High oblique photographs–the camera axis has a higher degree of tilt–approximately 60 degrees–which covers a larger area, and the horizon is visible in the photograph. In contrast with vertical photographs, this level of tilt produces a great deal of relief. That allows you to better identify natural or manmade features.
The decision to use vertical versus oblique photographs is partially dependent on the flying conditions. It is difficult for you to take vertical aerial photographs in turbulent, unstable conditions, and therefore, many photographers opt to take aerial photographs with a tilted camera axis.
You label an image oblique if the camera axis is tilted more than 3 degrees. Those tilted less than 3 degrees are still considered to be vertical photographs as opposed to oblique photographs. Oblique photographs are helpful to reveal the topography in relief, which is useful for identifying geological or archaeological features. Vertical photographs are better for mapping.
What’s the difference between high and low oblique aerial shots?
The difference is in the degree of tilt of the camera axis. With vertical photographs, the tilt is 3 degrees or less. If the tilt is sufficient to capture the horizon in the aerial photograph (60 degrees from vertical or more), then it is a high oblique aerial photograph. If not (approximately 30 degrees from vertical), it means the tilt is less, and that makes it low oblique.
There are two kinds of aerial photographs based on scale.
- Large scale aerial photographs–when the airborne aircraft is flying at a lower elevation, the camera captures images of less area, but the objects are seen in a bigger dimension. That means that the ratio of photo distance to the ground–or representative fraction–is of higher value. That’s why the experts call low elevation photographs large scale photographs. Large scale photographs are more useful for mapping land features and measuring objects.
- Small scale aerial photographs–When the aircraft is flying at a higher elevation, there is a larger area that can be covered in a single image, but the ratio of size of objects in the photograph relative to the ground dimension is actually smaller. That’s why the pros call these types of aerial photographs small scale photographs. Small scale photographs are helpful for studying large areas with features that don’t need to be mapped or measured in detail.
Once again, the selection of large or small scale photographs depends on the reason for the photography and the subject.
What’s the difference between large and small scale aerial photography?
Larger scale aerial photographs (e.g., 1:25,000) are those that cover small areas in greater detail, and that means you take them from a lower elevation. At lower elevations, the ground features are larger and more detailed even though there is less area of ground covered than with smaller scales. Small scale photographs (e.g., 1:50,000) cover larger areas from a higher elevation, but the areas covered reveal less detail. There is more area of ground covered than in large scale photographs.
Film and Filter Aerial Photography
You can use these film categories to produce photographs that vary in properties and can be used in different types of applications.
- Panchromatic Images–this refers to the type of film used, which captures all visible wavelengths of energy. The image is in grayscale, and often used for reconnaissance or map study.
- Color Photographs–color film can capture various visible bands separately. This type of aerial photography can be used to interpret objects within a study area.
- Infrared Imagery–this refers to the use of infrared film, which records only infrared energy. This type of photography is used to study vegetation and bodies of water, for example.
- Color-Infrared Imagery–this combines color and infrared film for vegetation studies, water body mapping, and a variety of urban applications.
- Thermal infrared imagery–this captures not only infrared images, but temperature variations as well. Experts use this type of imagery for temperature studies.
- Radar imagery–this film captures radar waves or microwaves, which typically contain a lot of noise and require correction. Experts use these images for weather applications and tecto-morphic studies.
- Spectra-zonal images–these images capture portions of the electromagnetic spectrum and you can use them for mapping applications.
How to Take Aerial Photographs?
You take these photographs by fixing the camera to a platform on an airborne craft, such as an airplane, helicopter, hot air balloon, or drone. Photographers have even attached cameras to kites and used them to photograph archaeological sites. You can then trigger the mounted camera automatically or remotely. It is also possible for a photographer in an airplane or hot air balloon to hold the camera and take the image.
Uses of Aerial Photography
Aerial photography is one of the earliest forms of remote sensing. Even today, it is still one of the more widely used and cost effective methods for this purpose. Before the advent of modern photographic methods, traditional photographers used in this method for remote sensing as well as for a variety of other uses.
Modern equipment has improved the quality, resolution, and platforms making this niche cheaper and more accessible than ever before. This kind of photography has a broad range of uses. Additionally, the fact that it has been used for a long time means it can provide us with a historical perspective of landscape changes through time.
One of the main uses of vertical aerial photographs is for mapping. Aerial photographers use both vertical and oblique photographs for planning land-use projects, movie production, environmental studies, archaeology, power line inspection, oil and gas surveying, surveillance, commercial advertising, and even artistic projects.
You can use different types of oblique and vertical photographs are to identify water features, find ruptures in oil and gas lines, and locate archaeological features. In wartime, photographers use aerial photographs to locate targets. And, given advances in drone technology, the applications for this niche are growing.
Lens System for Aerial Photographs
Aerial photography normally involves a minimum of two camera lenses attached together, which is known as a 2-lens system, but you can also use more lenses. For example, you can use a 3-lens systems to capture areas from horizon to horizon. As an example, photographers used this type of system, also called a trimetrogen system, in World War II to map enemy territory.
Best Time of the Day for Aerial Photography
Of course, the answer to this question depends on what you’re hoping to photograph. If you’re aerial mapping, and you don’t want shadows, the best time of day will be close to noon. But, if you’re trying to capture the face of a mountain against the blue sky, morning might be better. The golden hour is also good if you’re hoping to capture stunning images full of color.
Aerial photography is clearly an important photographic niche. It is one that is growing in popularity and use. With a solid understanding in the various types of aerial photography as well as their uses, aspiring aerial photographers can build an interesting, rewarding, and lucrative career.
Disadvantages of Aerial Photography
Some of the disadvantages include the fact that weather conditions can cancel a shoot. Additionally, it can be difficult to identify land features which can be obscured by environmental features, such as trees. Moreover, detailed variations in terrain features can be difficult to see without overlapping photographs and/or stereoscopic viewing instruments. Also, in poor light, a lack of contrasting colors and tone can render an aerial photograph useless
Aerial Photogrammetry vs. Terrestrial Photogrammetry
Photogrammetry combines photography and geography. The difference relates to how you take aerial photographs. With aerial photogrammetry, you take the images from an airborne craft whereas with terrestrial photogrammetry, you take the photos from a camera at a fixed, elevated terrestrial position. There is also, of course, a difference in the equipment and support required for each. Aerial photogrammetry requires much more support and investment than terrestrial photogrammetry.