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Aerospace images contain a wide variety of terrain information. However, objects on them appear in an unusual form and therefore often remain unrecognized by an unprepared observer. But you can learn to read pictures just like letters or notes. Reading aerospace images is called decoding.

In the process of decoding aerospace images, experts recognize objects of interest to them, knowing their distinctive decoding features. Among the many deciphering features, there are five main ones – the shape of the object, its size, color (or tone, if the picture is black and white), which fell from the object shadow, picture of the image. It is also very important to take into account the relationship, the interdependence of objects and phenomena in nature, which allows you to obtain information about hidden objects and processes that are not even depicted in the pictures.

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The technology and organization of deciphering work significantly depend on its tasks, territory, scale and type of images (photographic or scanning, thermal, radar, etc.), the use of single images or their series (multi-zone, multi-time). There are various organizational and technological schemes of decipherment, but they all include the following stages:

  • Acquaintance with methodical recommendations on this type of deciphering, literature and cartographic materials on object and area of researches;
  • Detect a set of deciphering objects:
  • Compilation of a preliminary legend of the future decipherment scheme or map.
  • Selection of images for decipherment, conversion of images to increase their expressiveness, preparation of devices and aids for decoding. It should be borne in mind that images that are optimal for one task may not be effective for another.

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Simple deciphering features – shape, size, tone (color) of the image and shadow. Indirect signs are based on connections between objects, on possibility of detection of objects invisible on a picture on other objects. Indirect signs are also the location of the object, geographical neighborhood, traces of the object’s impact on the environment. Each object has its own characteristics, which are manifested in direct and indirect deciphering features, which are generally not constant, but depend on the season, time and spectral ranges of shooting, the scale of images, etc. Thus, the tone of the depiction on the images in the visible range depends on the brightness of objects, in the thermal infrared – on their temperature, and in the radio range – on the surface roughness, moisture content, the geometry of the light beam. In thermal infrared images there is no such deciphering feature as a shadow, and in radar images, the use of the image structure of the plains is complicated by the presence of speckle noise. Depending on the specific conditions, the relative significance of the deciphering features and the features themselves change.

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