- signature
- i. The characteristic pattern of a target displayed by detection and identification equipment. It can be a radar, IR (infrared), acoustic, or Doppler signature. See also radar signature.An example of infrared signature of a helicopter.ii. As it relates to air-photo interpretation, it is the visual characteristics of objects on an air photograph that allow one to differentiate them. These characteristics include the tone, shape, size, pattern, texture, and shadow. Tone refers to the relative brightness or colors of an object in an image. Generally, tone is a fundamental element for distinguishing between different targets or features. Variations in tone also allow the elements of the shape, texture, and pattern of objects to be distinguished. Shape refers to the general form, structure, or outline of individual objects. Shape can be a very distinctive clue for interpretation. Straight-edge shapes typically represent urban or agricultural targets, whereas natural features, such as forest edges, are generally more irregular in shape. The size of objects in an image is a function of scale. It is important to assess the size of a target relative to other objects in a scene to aid in the interpretation of that target. Pattern (pattern) refers to the spatial arrangement of the visibly discernible objects. Typically, an orderly repetition of similar tones and texture will produce a distinctive and ultimately recognizable pattern. Orchards with evenly spaced trees and urban streets with regularly spaced houses are good examples of pattern. Texture refers to the arrangement and frequency of tonal variation in a particular area of the image. Rough textures would consist of a mottled tone where gray levels change abruptly in a small area, whereas smooth textures would have very little tonal variation. Shadow is also helpful in interpretation, as it may provide an idea of the profile and relative height of a target(s).
Aviation dictionary. 2014.