Aerial photographic and satellite image interpretation

The most basic are the elements of image interpretation: location, size, shape, shadow, tone/color, texture, pattern, height/depth and site/situation/association.

[4]Oblique aerial photographs are captured when the cameras are set at specific angles to the land.

[2] It allows the vision to pass through a relatively high proportion of the plant cover and leaves of trees.

[3] The horizon, the dividing border between planet and atmosphere from a viewing angle,[6] is unobservable in a low oblique aerial photograph.

[5] The length between two points is unable to be calculated and is not accurate because a low oblique image does not have a scale.

[5] Low oblique photographs can be used as a reference before site investigation because they give updated details of local places.

[5] High oblique aerial photographs are widely used in assisting field investigation because the line of sight shown is more similar to humans.

[5] Topographic maps are precise, in-depth descriptions of the terrain characteristics found in the areas or regions.

[7] Black and white aerial photography is capable of producing good-quality images under poor weather conditions, such as foggy and misty air.

[5] The degradation of trees driven by the insects can also be identified using color aerial photos.

[5] It can assist in locating storage of materials in the natural environment, such as trees, wild animals and oil.

[2] This phenomenon is due to the fact that plants reflect more infrared radiation (IR) than man-made objects.

[2] High-altitude aerial photographs are taken when the plane is flying in the altitude range of 10,000 to 25,000 feet.

[2] The advantage of high-altitude aerial photography is that it can record the information of a larger area by taking one photograph only.

[9] An aerial photograph marks different data and information about the covered area and the airplane's position and condition.

[2] The purpose of overlapping the aerial photography is to generate the 3D topography or relief when using a stereoscope for interpretation.

[2]The preferred orientation of an aerial photograph is closely related to the position of the Sun and the shadow element.

[4] A datum plane, which refers to the average sea level, is essential in the displacement phenomenon.

[4] For a location which has an elevation higher than that of the datum plane, the original position will move away from the central point of the image.

[4] For a location which has an elevation lower than that of the datum plane, the original position will move closer to the central point of the image.

[4] Distortion refers to any change in an object's or region's location on an aerial photo that modifies its original features and shapes.

[4] This is a process used to modify the exposed photo film to generate an aerial photograph.

Photo interpretation at the U.S. National Photographic Interpretation Center during the Cuban Missile Crisis .
Figure 2: The principle of vertical aerial photography. [ 3 ] [ 4 ]
Figure 3: The principle of low oblique aerial photography [ 3 ] [ 4 ]
Figure 4: The principle of high oblique aerial photography. [ 3 ] [ 4 ]
Figure 5: The principle of scale of aerial photographs [ 4 ] [ 2 ]
Figure 8: Details on an aerial photograph. It includes the focal length , flying height , location, photo number, recorded time and date, etc. [ 2 ]
Figure 9: This diagram describes the principle of the overlapping of two covered areas along a single flying path. [ 2 ]
Figure 10: This diagram shows the position of the Sun (south). When the sunlight is from the south direction, the shadow is usually in the north direction. Therefore, the airplane which flies from north to south can clearly record the shadow elements of the objects. [ 2 ]
Figure 11. This diagram shows an example of displacement. A is the location that is lower than the datum plane. It moves inward to the central point. B is the location that is higher than the datum plane. It moves away from the central point. These locations are displaced in the opposite direction. [ 4 ]
Figure 12: An example of a mirror stereoscope .