The beauty of photography

QUESTION:EXPLAIN 7 TOOLS USED IN INTERPRETING IMAGES

Photographic interpretation is the act of examining photographic images for the purpose of identifying an object and judging their significance. There are a variant number of tools which are used to aid in aerial photo interpretation such as tone, colour, texture, pattern, shadow and time.

Tone refers to the relative brightness or color of elements on a photograph and generally, tone is the fundamental element for distinguishing between different targets or features. Variations in tone also allow the elements of shape, texture, and pattern of objects to be distinguished. On black and white photographs, tone varies from white to black with various shade of grey in between. The tone of an object provides more information than any other single element of object recognition.

Size is also a tool that is used and it must be considered in the context of the scale of a photography. Size is a function of scale and it is important in assessing the size of a target relative to other objects in a scene, as well as the absolute size, to aid in the interpretation of that target. A quick approximation of target size can direct interpretation to an appropriate result more quickly. For example, if an interpreter had to distinguish zones of land use, and had identified an area with a number of buildings in it, large buildings such as factories or warehouses would suggest commercial property, whereas small buildings would indicate residential use.

Texture refers to the arrangement and frequency of tonal variation in particular areas of an image. Rough textures would consist of a mottled tone where the grey levels change abruptly in a small area, whereas smooth textures would have very little tonal variation. Smooth textures are most often the result of uniform, even surfaces, such as fields, grasslands. A target with a rough surface and irregular structure, such as a forest canopy, results in a rough textured appearance. Texture is one of the most important elements for distinguishing features in radar imagery. It is more useful in interpretation of larger groups of objects like tree stands.

Shadow is also helpful in interpretation as it provide an idea of the profile and relative height of a target or targets which may make identification easier. Shadows can also reduce or eliminate interpretation in their area of influence, since targets within shadows are much discernible from their surroundings. Shadow is also useful for enhancing or identifying topography and landforms, particularly in radar imagery. It also depends on the time of photography and direction of the photographer and also wind, affects the shadows and makes identification difficult.

Pattern refers to the spatial arrangement of visible objects. A repetition of similar tones and textures 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 and are useful to identify an object and its usage.

Shape refers to the general form, structure, or outline of individual objects. Shape can be a very distinctive clue for interpretation and for example straight edge shapes typically represent urban or agricultural (field) targets, while natural features, such as forest edges, are generally more irregular in shape, except where man has created a road or clear cuts. Farm or crop land irrigated by rotating sprinkler systems would appear as circular shapes.

Time is also a tool used to interpret aerial photography and it refers to temporal characteristics of a series of photographs that can be helpful in determining the historical change of an area for example looking at a series of photos in a city taken in different years can help determine the growth of suburban neighborhoods and the image below can indicate how time aids in the aerial photography interpretation.