UNIT-1 Types and Acquisition of Aerial Photographs.pptx

UNIT-1 Types and Acquisition of Aerial Photographs.pptx

1. Types and Acquisition of Aerial Photographs Miss. Malvika Gohil SEM-4 RS-Geology Unit-1

2. What is aerial photography and What are the types of aerial photography? Aerial photography is a general term used to describe the taking of photographs from an elevation, usually with the use of some sort of equipment such as an airplane, rocket, hot air balloon or drone. While any photo taken from an elevation can be considered aerial, there are various types of aerial photographs that are divided by particular elements including the camera axis, the scale of the image and the type of film used . The  types of aerial photographs  based on camera axis include vertical, low oblique and high oblique. Each type covers a certain amount of area and involves tilting the camera to a specific degree. The result when these factors are applied can be striking . 1.   Vertical Photographs  – in this type of photo, the camera axis is in a vertical position, resulting in an image with little or no relief and a relatively small amount of area covered.  As vertical images have a direct, overhead result they are often used in mapping.

3. What is aerial photography and What are the types of aerial photography? 2. Low Oblique Photographs  – to take this type of photo you need to tilt the camera axis more than three degrees. In this case, the horizon will not be visible in the final image and the image will be somewhat distorted as a result. These photos can be useful for taking close up shots that require more detail, such as those used for advertising . 3.      High Oblique Photographs  – here the camera axis is tilted to approximately 60 degrees, which allows for a larger area to be covered and will include the horizon in the final shot. This gives you a better wide view of an area which allows you to identify geographical features and landmarks . Generally speaking, vertical photographs are more useful for mapping purposes but it can be more difficult to take vertical photos in unstable weather conditions. By contrast, oblique photos are easier to take in a wide variety of weather conditions, so most  photographers  prefer this type of photography. Since oblique photos produce final images with a wider view, they are more useful for topography, geographic surveys and identifying archaeological features.

4. Aerial photography on the basis os scale. There are also two types of aerial photographs that are based on scale: large scale and small scale. The scale is dependent on the altitude of the aircraft and can vary in sharpness and detail, much like the photo types based on axis. Generally speaking, larger scale photos cover small areas in greater detail while small scale photos cover large areas with less detail.   Large Scale Photographs  – these are taken with the aircraft flying at a lower elevation, resulting in less area captured by the camera but objects seen in bigger dimension. This type of photo is more useful for mapping land features or measuring specific objects. They would be more likely to be used for marketing or for getting a closer look at a property to scan for damage or other issues. Small Scale Photographs  – small scale photos are taken when the aircraft is flying at a higher elevation, allowing for a larger area to be covered in a single photo.  While the area covered is larger, the ratio of size of any objects in the photo relative to the ground would be smaller, which is why these photos are considered small scale. This type of photo is useful for studying larger areas where specific mapping or measurement of features isn’t necessary.

5. Large scale and Small scale image Large scale image Small scale image

6. T ypes of aerial photography that depend on the film used Panchromatic Photographs  – these are images in grayscale, where color is not important. They are used for reconnaissance or map study. Color Photographs  – color aerial photography, much like color photos taken on land, can render images in greater detail and can be helpful for identifying specific objects within a large area. Infrared Photographs  – these images record only infrared energy and are generally used to study vegetation, bodies of water and other geographical features .   Color-Infrared Photographs  – these combine color and infrared technology for mapping, geographic studies and urban photography. Thermal Infrared Photographs  – these images capture both infrared energy and temperature variations and can be used for temperature studies or location. Radar Imagery  – this captures radar or microwaves and is generally used for weather and other scientific applications. Spectra-zonal Images  – these capture parts of the electromagnetic spectrum and are used for mapping purposes.

7. Panchromatic Photographs Color Photographs Infrared Photographs

8. Thermal Infrared Photographs Radar Imagery Spectra-zonal Images

9. Types d epending on the purpose of the photos Panoramas  – these are wider shots that are created by stitching together several photographs taken at different angles from the same spot or from different spots at the same angle. Stereo Photography  – this is actually a range of techniques that are employed to create 3D images using different photographs of the same area taken from different spots. Pictometry  – this technique uses five rigidly mounted cameras to produce one vertical and four low oblique photos that can then be used together. Orthophotos   – in this technique, vertical photos are geometrically corrected by removing perspective and adjusting for variations in terrain. This results in images which can be more closely aligned with “real world” coordinates and are commonly used for mapping.

10. Types depending on the purpose of the photos Panoramas Stereo Photography

11. Types depending on the purpose of the photos Pictometry Orthophotos