Theory of interpretation of aerial and space images. Image decryption

Visual deciphering method, direct and indirect signs of deciphering.

Materials used in visual interpretation

The concept of deciphering images. Decoding classification.

Decoding (interpretation) called the analysis of video information in order to extract information about the surface and interior of the Earth (other planets, their satellites), objects located on the surface, processes occurring on the surface and in near-surface space.

The composition of information includes, for example, the determination of the spatial position of objects, their qualitative and quantitative characteristics, the determination of the boundaries of the strike of the processes under study and data on their dynamics, and much more. The tasks of deciphering also include obtaining from other sources information that cannot be read directly from images, for example, information about the presence, position and properties of objects not displayed, names of settlements, rivers, natural boundaries. Such sources can be materials of previously performed decoding, plans, maps, auxiliary images, reference literature, the terrain itself.

Other definition of decipher:

Deciphering pictures (interpretation) - the process of recognizing local objects from a photographic image and identifying their content with the designation of qualitative and quantitative characteristics by conventional signs .

Depending on the content, decoding is divided into:

general geographic

special (thematic, branch).

General geographic interpretation includes two varieties:

Topographic interpretation- is performed to detect, recognize and obtain the characteristics of objects that should be depicted on topographic maps. It is one of the foundations of the processes of the technological scheme for updating and creating maps.

landscape interpretation– is carried out for regional and typological zoning of the area and the solution of special problems.

Special (thematic, sectoral) interpretation produced to solve departmental tasks to determine the characteristics of individual sets of objects. There are many types of thematic interpretation. agricultural, forestry. geological, soil, geobotanical, etc. and other departmental purposes. If the ultimate goal of special interpretation is the compilation of thematic maps, such as agricultural, soil or geobotanical, then. in the absence of a suitable topographic basis, a special interpretation is accompanied by a topographic one.

The basis of the methodological classification of deciphering into its modern level development are the means of reading and analyzing video information. Based on this, the following main decryption methods can be distinguished:

visual, in which information from images is read and analyzed by a person:

machine-visual, in which video information is preliminarily converted by specialized or universal interpretation machines in order to facilitate subsequent visual analysis of the resulting image:

automated(dialog), in which reading from images and analysis. or direct analysis of line-by-line recorded video information, are performed by specialized or universal interpretation machines with the active> part of the operator:

auto(machine), in which deciphering is performed entirely by interpretation machines. A person defines tasks and sets a program for processing and video information.

In all methods, the lower levels of classification can be distinguished - methods and variants of methods.

The principle scheme of the decryption process in any method remains unchanged - recognition is performed by comparing and determining the degree of proximity of a certain set of features of the object being decoded with the corresponding reference features that are in the memory of a person or machine. In this case, the recognition process is preceded by a learning process (or self-learning), in which a list of objects to be deciphered is determined, a set of their features is selected, and an acceptable degree of their difference is established.

With insufficient a priori information about the classes of objects and their features, a person and a machine can divide the depicted objects according to the proximity of some features into homogeneous groups - clusters, the content of which is then determined by a person or machine using additional data.

2. Visual method of deciphering, direct and indirect signs of deciphering .

Natural objects depicted in the images can be identified and interpreted by the decoder according to their properties, which are reflected in the deciphering features of these objects. All deciphering signs can be divided into two groups: direct deciphering signs and indirect ones.

Direct signs include those properties and characteristics of objects that are directly displayed on the images and can be perceived visually or using technical means.

To direct deciphering signsm include the shape and dimensions of the image of objects in plan and height, the overall (integral) tone of black-and-white or color of color (spectrozonal) images, and the texture of the image.

The form in most cases, it is a sufficient sign to separate objects of natural and anthropogenic origin. Objects created by man, as a rule, are distinguished by the correct configuration. So, for example, any buildings and structures have regular geometric shapes. The same can be said about canals, highways and railways, parks and squares, arable and cultivated fodder lands and other objects. The shape of objects is sometimes used as an indirect sign to determine the characteristics of other objects.

Dimensions of objects to be decrypted in most cases are evaluated relatively. The relative height of objects is judged directly from their image at the edges of images obtained using wide-angle imaging systems. The size, as well as the shape in height, can be judged by the shadows falling from objects. Of course, the area on which the shadow falls must be horizontal.

The dimensions of the image of objects, as well as the shape, are distorted due to the influence of the terrain and the specifics of the projection used in the filming system.

Image tone is a function of the brightness of the object within the spectral sensitivity of the radiation receiver of the imaging system. In photometry, the analogue of tone is the optical density of the image. the variability of this feature is associated with the following factors: lighting conditions, surface structure, type of photographic material and its processing conditions, electromagnetic spectrum zones and other reasons. gray, etc. The number of steps is determined by the threshold of light sensitivity of the human visual apparatus.

It has been experimentally established that the human eye It has been experimentally established that the human eye can distinguish up to 25 gradations of gray tone; for practical purposes, a gray tone scale from seven to ten steps is more often used (Table 2).

Table 1Quantitative characteristics of image density

With the help of computers, it is possible to distinguish up to 225 gray levels from photographs and films. In addition, these levels, depending on the task, can be grouped according to certain steps with their quantitative characteristics. The textural properties of objects, on which the distribution of light reflected from the surface of the object into space, have a significant influence on the tone of the photographic image.

Optical density serves as a code that conveys the properties of objects. Objects that are completely different in color can be displayed in a black and white photograph or television image in the same tone. Given the instability of the indicator, when deciphering, the phototone is evaluated only in combination with other deciphering features (for example, structure). Nevertheless, it is the phototone that acts as the main deciphering feature that forms the outlines of the boundaries, the dimensions and structure of the image of the object.

Tone can be a fairly informative sign with the right elements of the shooting system and shooting conditions.

The tone of the image of arable land can vary significantly in time and space, since it significantly depends on the state of the surface of unoccupied fields (plowed, harrowed, dry, wet, etc.), on the type and phenophase of crops on occupied fields.

Image color is a spectral characteristic and determines the energy of the light flux. The color gamut of images is an essential sign of interpretation. This sign should be considered in two aspects. In the first case, when the image on aerial and satellite images is formed in colors close to natural colors (color images), the recognition and classification of terrain objects does not cause any particular difficulties. In this case, such color characteristics as its lightness and saturation are taken into account, as well as various shades the same color. In another case, a color image is formed in arbitrary colors (pseudo-colors), as is the case with spectral-zonal imaging. The meaning of this conscious distortion colors nature in the image lies in the fact that in the images the observer perceives the color contrasts of image details more easily, therefore color aerial and space images have a higher decipherability than black and white ones. The best results are obtained when deciphering multispectral aerial photographs with a higher color contrast.

The colors of a multispectral aerial photograph are less stable than those of a natural color photograph. If necessary, they can be significantly changed with the help of light filters.

There is a special technique in deciphering when color in images is used to encode image details that have the same optical density. This method is widely used in the interpretation of zonal images obtained as a result of multizonal surveys. It is very effective in landscape interpretation. In this case, individual elementary landscape units can be coded in some color, based on their related features and properties.

Shadow as a deciphering feature plays an important role in deciphering objects and their properties. The falling shadow cast by an object on the earth's surface, located on the side opposite to the Sun, emphasizes the volume of the object and its shape. Its shape and size depend on the height of the Sun, the terrain (area) on which the shadow falls, and the direction of illumination.

There are several ways to determine the height of an object from a drop shadow:

where l is the length of the shadow of the object on the aerial photograph;

m - image scale denominator;

n is the relative length of the shadow, which is taken from the tables of V.I. Drury (see Smirnov L.E., 1975)

where b₁ is the length of the shadow of the object on the aerial photograph;

h₂ is the height of a known object on an aerial photograph;

b₂ is the length of the shadow on an aerial photograph of a known object

The shape of the falling shadow can be used to recognize both artificial objects (buildings, pillars, triangulation points) and natural objects. Falling shadows are widely used as signs of interpretation in the study of vegetation. .Drop shadows display the elongated shape of the object's silhouette. This property is used when deciphering fences, telegraph poles, water and silo towers, outdoor signs of geodetic network points, individual trees, as well as pronounced landforms (cliffs, gullies, etc.). It should be borne in mind that the size of the shadow is influenced by the terrain. Each breed has its own specific crown shape, which is reflected in its shadow and allows you to determine its species composition. For example, the shape of the falling shadow of a spruce resembles an acute triangle, while that of a pine tree is oval. However, it should be remembered that the shadow is a very dynamic deciphering feature (it changes during the day). It can exceed the size of an object when the Sun is low above the horizon.

Texture (image structure) - the nature of the distribution optical density across the image field of the object. The structure of the image is the most stable direct decoding feature, practically independent of the shooting conditions. The structure is a complex feature that combines some other direct deciphering features (shape, tone, size, shadow) of a compact group of homogeneous and heterogeneous details of the terrain image in the image. The repeatability, placement and quantity of these details lead to the identification of new properties and contribute to an increase in the reliability of interpretation. The importance of this feature increases as the image scale decreases. For example, the texture of a forest massif is formed by the image of the crowns of individual trees in the photographs, and with a high resolution of the shooting system - by the image of crown elements - branches or even leaves; the texture of pure arable land is formed by the display of arable furrows or individual clods.

There is a fairly large number of structures formed by combinations of points, areas, narrow bands various shapes, width and length. Some of them are discussed below.

grain structure characteristic of the image of forests. The pattern is created by gray spots of a rounded shape (crowns of trees) on more dark background created by shaded gaps between trees. The image of cultivated vegetation (gardens) has a similar structure.

Homogeneous structure It is formed by the same type of microrelief and is characteristic of low-lying grassy swamps, steppe plains, clay deserts, and reservoirs in a calm state of water.

Banded structure typical for images of vegetable gardens and plowed lands and is a consequence of the parallel arrangement of furrows.

Fine grained structure typical for the image of shrubs of various species.

mosaic structure It is formed by vegetation or soil cover of unequal moisture content and is characteristic of randomly located areas of various colors, sizes and shapes. A similar structure, created by the alternation of rectangles of various sizes and densities, is typical for the image of personal plots,

Spotted structure typical for images of gardens and swamps.

Square structure characteristic of some types of forest swamps and urban-type settlements. It is formed by a combination of forest areas separated by light stripes of a swamp, and is read as a combination of areas of a uniform tone. The same structure is created by images of multi-storey buildings (relatively large rectangles) and elements of intra-quarter development in settlements.

As the scale decreases, the texture is created by larger terrain elements, for example, individual fields of arable land. Texture is one of the most informative features. It is by texture that a person unmistakably identifies forests, gardens, settlements and many other objects. For these objects, the texture is relatively stable in time.

Indirect signs can be divided into three main groups. natural, anthropogenic and natural-anthropogenic. Indirect deciphering signs are quite stable, and depend on the scale to a lesser extent.

To natural include the relationship and interdependence of objects and phenomena in nature. They are also called landscape. Such features can be, for example, the dependence of the type of vegetation cover on the type of soil, its salinity and moisture, or the relationship of the relief with the geological structure of the area and their joint role in the soil-forming process.

By using anthropogenic indirect signs identify objects created by man. In this case, functional links between objects, their position in the general complex of structures, zonal specificity of the organization of the territory, communication support of objects are used. For example, the livestock farm of an agricultural enterprise can be identified by the combination of main and auxiliary buildings, interior layout territory, intensively carved runs, the position of the deciphered complex of structures relative to the residential area, the nature of the road network. Similarly, repair shops are identified by the image of the vehicles located on the territory, the stud farm is reliably identified by the arena adjacent to its territory. At the same time, each of the structures of the complex separately, without connection with others, is not deciphered. . For example, a light winding line connecting settlements is almost certainly an image of a country road; with the same probability, light winding lines lost in a forest or in a field are field or forest roads; the construction near the intersection of a light winding strip (dirt road) with the railway indicates the presence of a crossing here; a road that breaks off on the bank of the river and continues on the other side indicates the presence of a ford or ferry; a group of buildings near a multi-branching railway suggests the presence of a railway station. Logical analysis of direct and indirect deciphering signs significantly increases the reliability of deciphering.

To natural-anthropogenic indirect features include, the dependence of human economic activity on certain natural conditions, the manifestation of the properties of natural objects in human activity, and more. For example, according to the placement of certain types of crops, it is possible to make a certain judgment about the properties of soils, their moisture content; according to the change in surface moisture at the locations of drains, the elements of a closed drainage system are deciphered. Objects used in the identification and determination of the characteristics of objects that cannot be deciphered directly are called indicators, and the decryption indication. Such decryption can be multi-stage, when the direct indicators of decipherable objects are identified with the help of auxiliary indicators. Methods of indication interpretation solve the problems of detecting and determining the characteristics of objects that are not displayed on the images. The most important indicators of various phenomena in indirect interpretation are vegetation, relief, and hydrography.

Vegetation is a good indicator of soils, Quaternary sediments, soil moisture, etc. When deciphering, the following indicative signs of vegetation can be used:

Morphological features make it possible to distinguish woody, shrubby, and meadow vegetation in aerospace images.

Floristic (species) signs make it possible to decipher the species composition, for example, pine plantations are confined to sandy automorphic soils, black alder plantations to soddy-gley soils.

Physiological signs are based on the relationship of hydrogeological and geochemical conditions of the place of growth with chemical properties breeds. For example, on limestones, lichens are orange, and on granites they are yellow.

Phenological features based on differences in the rhythms of vegetation development. This is especially well manifested in autumn in deciduous vegetation in a change in leaf color. On color aerospace images, the species composition of vegetation is clearly distinguished, which emphasizes the growing conditions.

Phytocoenotic features make it possible to decipher the types of forest vegetation and associations of meadow vegetation, which are confined to certain growing conditions. For example, lichen pine forests grow on elevated relief elements with automorphic loose-sandy soils, long-moss pine forests are confined to lower relief elements and soddy-podzolic-boggy soils.

Relief is one of the most important indicators. The connection of the relief with other components of natural complexes, its great role in the formation appearance landscapes and the possibility of direct interpretation make it possible to use the relief as an indicator of a wide variety of natural objects and their properties. Such indicators can be the following morphometric and morphological features of the relief: a) absolute heights and amplitudes of height fluctuations in a given area; b) the general dissection of the relief and the angles of inclination of the slopes; c) orientation of individual landforms and exposure of slopes (solar, wind), which, together with absolute heights, determine climatic conditions and water regime in this territory; d) connection of relief with geology; e) the genesis of the relief, its age and modern dynamics, etc.

Hydrography is an important indicator of physical-geographical and geological conditions. The close relationship between the structure and density of the hydrographic network (lakes, rivers, and swamps) and geology and relief makes it possible to use aerial photographs, especially of the river network, as a direct landscape feature in the analysis of terrain in geomorphological, geological, and paleographic terms.

Deciphering signs are usually used collectively, without dividing them into any groups. The image on the deciphered area is usually perceived by a person as a whole - a terrain model. Based on the analysis of the model, we create a preliminary hypothesis about the essence of the object (phenomenon) and its properties. The correctness of the hypothesis is confirmed or rejected (sometimes multiple times) with the help of additional features.

5. Information properties of images from the point of view of visual interpretation

Two characteristics are used to evaluate the information properties of an image:

1. informative;

2. . decipherability.

informative - expert assessment of the potential possibility of obtaining the necessary information about objects from these images. It is impossible to select a quantitative criterion for assessing the information content of an image. information content is usually assessed verbally: high information content, insufficient information content, etc. Depending on the goals of deciphering (tasks to be solved), the same images can be recognized as highly informative and insufficiently informative.

A formal assessment of the amount of information contained in an image can be based on its relationship with resolution. The higher the resolution of the images, the more information they contain. On the basis of semantic information, it is possible to determine its value for the researcher. For example, a clear image of the species composition of forest vegetation on infrared aerial photographs indicates the effectiveness of using these images to decipher its species composition. By deciphering the aero satellite images you can get a wide variety of information, facts. However, information includes only those that meet the task, goal.

To determine the maximum amount of information, the concept of " full information", which should be understood as the information that in each particular case can be extracted from images obtained under optimal technical and weather conditions for shooting, as well as the scale. However, images with properties other than optimal are often used. The amount of information contained in them is generally less than the complete information and amounts to operational information. Operational information includes those of the necessary information that can be calculated: obtained by deciphering the image data. However, the extracted information is almost always less than operational due to decryption errors. Errors in decoding objects can occur for the following reasons: when decoding low-contrast objects; false identification of objects due to the coincidence of deciphering features (for example, limestones and snowfields). However, often the decoder encounters interference and noise that are of no value to the researcher. Interferences include the presence of glare, as well as the image in the images of the atmosphere, which is superimposed on the image in the form of haze, or atmospheric phenomena such as fog, dust storms, etc. The qualitative diversity and amount of extracted information is largely determined by the properties of the information field of images .

Simplicity comparison of images with nature, the external match of the image of objects with the way we see them, determine the clarity of the images. Objects are recognized in photographs if their image corresponds to a direct visual image and if it is well known from practice, for example, cloudiness. The visibility of photographs has always been especially appreciated. It was assumed that the possibility of direct visual recognition is the main advantage of images from aircraft. But with the development of the method great importance began to give expressiveness to the image. The image is the more expressive, the more intense and contrast the objects and phenomena that are the subject of interpretation are highlighted on it.

In this way, expressiveness images are characterized by the simplicity of deciphering objects and phenomena that are most essential for solving the problem. Visibility and expressiveness in a sense, opposite, mutually exclusive properties of the aerospace image. So, color in natural colors pictures. Color spectrum-zonal images are less clear, but when deciphering, for example, forest vegetation, they are more expressive. The clarity and expressiveness of the image are related to its scale, but the optimal expressiveness and clarity of the image scales do not coincide with each other. Visibility increases with zooming in.

Decipherability aerospace images is the sum of their properties that determine the amount of information that can be obtained by deciphering images to solve a given problem. It is known that the same images have different decipherability in relation to different objects and tasks. tasks. Quantitatively, it can be expressed through the ratio of operational information (I 0) contained in these images, and Ip of complete information:

However, often to determine the decipherability of images, relative decipherability is used, which is characterized through the ratio useful information(I) carried by the aerial photograph to the complete information that can be obtained from the aerial photograph:

The value of Dc is called the decipherability coefficient. The concept of "complete information" can be interpreted in different ways, in accordance with this, relative decipherability can characterize various properties of aerial photographs. If we take the maximum information capacity of aerial photographs as complete information, then the decipherability coefficient will show the load of aerial photographs with useless information, in other words, “noise level

The same formula (Dc = I / Imax) can also be used to calculate the relative decipherability of individual objects. With the appropriate approach, it allows you to compare aerial photographs taken on different films, printed on different paper etc. Thus, the value of an aerial photograph as a source of information is expressed through the coefficient of decipherability.

Completeness of decryption can be characterized in terms of the ratio of used (recognized) useful information (I 1) to all useful information contained in the data

aerial photographs:

The completeness of decryption depends to a large extent on the training of decryptors, their experience and special knowledge.

Under the reliability of deciphering one should understand the probability of correctly identifying or interpreting objects. It can be estimated through the ratio of the number of correctly recognized objects (n) to the sum of all recognized objects.

Decipherability can be improved by enlarging the image, changing the contrast, reducing blur, and other transformations.

It seems to the uninitiated person unusual and obscure. Unlike the map, it does not have symbols, explanatory captions. Therefore, one must be able to read pictures, or, as experts say, decipher them. Deciphering is based on knowledge of the distinctive deciphering features of objects - a kind of alphabet of images. Some of these signs are direct, they directly indicate which object is depicted in the picture. For example, white is a sign of snow or salt crust, the rectangular shape of land is a sign of plowed or sown fields, and the nature of the building can be determined by the shape of the shadow. The five main direct signs are shown in the figure. However, indirect signs are more significant. They allow you to get information about objects and processes that are not shown in the pictures, using their relationships. For example, the character in arid regions testifies to the depth of invisible groundwater and its saturation with mineral salts. Deciphering by indirect signs is called indicative. This complex type of geographic analysis provides information about objects invisible on the ground by their visible indicators.

Personal computers are often used to work with satellite images. A digital photograph can be displayed on a computer screen, enlarged or reduced, improved quality and made more contrast, colorized in various colors to look at an object from different angles. A series of zonal black-and-white images makes it possible to synthesize a color image by selecting such zones and light filters, on which the objects of interest to the researcher will stand out more clearly. Based on the analysis of the brightness of zonal images, the computer itself will identify homogeneous groups of objects, that is, it will perform an uncontrolled, uncontrolled classification. If the imaged objects are known for individual areas (they are called test, reference), then the computer, by analogy, will select the same objects in the rest of the image, i.e., it will perform a controlled classification.

Here is an example of such a computer processing of a satellite image of the central part, where the Severonickel copper-nickel plant operates on the shore of Lake Imandra in Monchegorsk, whose smoke emissions have a detrimental effect on the vegetation of nearby territories.

In the image, areas of damage and destruction of vegetation are distinguished by the color of the image - their red-brown spots contrast sharply with the greenish tones of the still preserved forests. The computer map compiled as a result of the controlled classification shows the distribution of zones with varying degrees industrial impact on vegetation. The repetition of such a classification based on images taken in different years makes it possible to monitor the change in the degree of impact, which is necessary for carrying out restoration and environmental protection measures.

Two images of the same area, obtained from different points, form a stereoscopic (i.e., recreating a three-dimensional image) pair. Armed with a special optical device - a stereoscope, one can observe a three-dimensional, very expressive model of the terrain. This remarkable property of photographs is important for studying the relief of the earth's surface. Using stereophotogrammetric instruments, such a relief model is measured with great accuracy. So, stereopairs are used to make maps of the area, primarily topographic ones. Now such work is performed using a computer, using special stereo glasses.

Image decryption

Image decoding

a method for studying territories, water areas, atmospheric phenomena based on their images on aerial, space, underwater photographs, photo schemes, photo plans. The essence of deciphering is deciphering the content of images, recognizing depicted objects, determining their qualitative and quantitative characteristics, extracting information based on the dependencies that exist between the properties of objects and their display in images.
By technical ways There are visual (camera and field, including aerovisual), instrumental (measuring) and automated interpretation, and often these methods are used in combination. According to the content, decoding is distinguished general geographical (including topographic), thematic (geological, landscape, ecological, etc.) and special (forest management, reclamation, etc.). The quality and reliability of object recognition is determined by the deciphering features, the scale and resolution of images, their stereoscopic properties, technical support and the algorithms used.
Decryption features are the characteristic features of objects by which they can be recognized, distinguished from others and interpreted. They are divided into direct and indirect. Direct signs are inherent in the objects themselves, these are the configuration, size, color, phototone, shadow from the object, the structure and texture of the image. Indirect(indicative) deciphering features characterize an object indirectly through the properties of some other object associated with it. For example, tectonic faults and ground water often found in photographs along the vegetation strips associated with them. In the decoding process, pre-prepared sets of reference features are usually used.
The decoder must certainly know the specific (geographical, geological, etc.) features of the territory and understand the nature of the deciphered object itself. The results are presented in digital form or they are drawn up in the form of decoding schemes, according to which the maps are then compiled, refined, and updated.
Modern automated decoding involves the use of special photogrammetric electron-optical devices, computers, software and information tools. Automation covers the entire cycle of work, including preliminary correction of images, selection, recognition and digitization of objects, drawing maps and displaying them on the screen or on a printer.

Geography. Modern illustrated encyclopedia. - M.: Rosman. Under the editorship of prof. A. P. Gorkina. 2006 .

See what "image decoding" is in other dictionaries:

interpretation of images in mudflow science- thoto–interpretation for mudflows INTERPRETATION OF IMAGES IN SELEVISION is one of the methods for studying mudflows, which is especially widely used in their mapping. It consists in recognizing mudflow basins on aerial and satellite images and ... ... Mudflow phenomena. Terminological dictionary

Interpretation of aerial photographs, one of the methods for studying the terrain from its image obtained through aerial photography. It consists in identifying and recognizing photographed objects, establishing their qualitative and quantitative characteristics, as well as ... ... Great Soviet Encyclopedia

Reading, transcribing, interpreting content. photographic and television shots made in decomp. intervals of the visible zone of the spectrum and infrared (IR) images in the range of 1.8-14 mkm. Shooting from space is made from manned space ... ... Geological Encyclopedia- 8.4.6 Interpretation of large-scale aerial and space images is performed for a retrospective assessment of the environmental situation.

Essence of decryption. Deciphering images as a method of studying territories, water areas, phenomena is based on the relationship between the properties of objects and the nature of their reproduction in images.

Decryption properties are a property of objects that are reflected in the image and used for recognition.

Deciphering a snapshot means detecting, recognizing, classifying and interpreting an identified object or phenomenon.

Decoding is the process of recognizing: objects, their properties, relationships by their images in the picture. This is also a method of studying and studying objects, phenomena and processes on the earth's surface, which consists in recognizing objects by their characteristics, determining characteristics, and establishing relationships with other objects.

2. The role and importance of deciphering when creating and updating topographic maps.

The process of interpretation in the preparation and updating of topographic maps is considered on a broad geographical basis, taking into account the complexity of the tasks being solved and the production orientation of mapping.

3. Types and methods of decoding.

Types of decryption. There are military, topographic, geological, agricultural, forestry, etc. decoding. When deciphering geographically, it is necessary to determine what is shown in the image. Depending on the goals of research and interpretation, the answer can be either simple (forest, pond, glacier) or more complex.

Currently, visual interpretation is the main and most common, since in it the object or phenomenon being studied is considered in spatial connection with its environment, which provides additional information that escapes during computer processing. Therefore, in order to obtain complex thematic information, they strive to integrate visual and computer interpretation, each of which has its own advantages and limitations.

4. Deciphering signs of images of terrain objects.

Deciphering signs are divided into direct and indirect.

The properties of objects that are directly reflected in the images are usually called direct deciphering features.

These include three groups of features:

Geometric (shape, shadow, size),

Luminance (phototone, brightness level, color, spectral image),

Structural (texture, structure, image pattern).

Direct deciphering features make it possible to recognize the objects depicted in the image, however, it is not always possible to determine their properties from them, that is, to interpret them, as well as to map objects that are not depicted in the images, to study processes and phenomena.

Indirect signs include interdependence and interconnections existing in nature between phenomena and objects reflected in aerial photographs: geomorphological, geobotanical, the relationship between the relief and the resistance of soils and rocks to erosion, weathering, etc.

For example, by the nature of the vegetation cover, one can judge the soil-ground and hydrogeological structure of the area, by the outline of the river channels in the plan, one can judge the type of the channel process, by the old rivers on the floodplains - its direction and pace, etc.

The use of other types of aerial surveys in combination with traditional planned aerial photography significantly expands the possibilities of interpretation: perspective, color, spectral-zonal, multi-zone, thermal, radar, airborne laser scanning, etc.

Decoding - answers the question of what is in this place snapshot (which object), i.e. the possibility of obtaining subject information about the object. A single deciphering process includes the following stages: detection, recognition and interpretation, as well as determining the qualitative and quantitative characteristics of objects and presenting the deciphering results in graphical, digital or textual form. There are military, topographic, geological, agricultural, etc. interpretation of images. In geographic interpretation, first of all, it is necessary to answer the question of what pictured. Depending on the goals of aerospace research, the content of this answer can be quite simple (forest, reservoir, glacier) or more complex (cedar forest heavily damaged by the Siberian silkworm; areas of the reservoir with different concentrations of suspended matter and phytoplankton). Classification technologies: cluster (based on the formal features that we set, the program distributes pixels into classes), classification with training (the decoder sets standards (trains the program)) Decoding has always been understood as the extraction of high-quality geoinformation from images when they are directly viewed. Currently, this is the main and most common way to extract information from images. During visual interpretation, the studied local object or phenomenon is always considered in spatial relationship with its environment, which provides important additional information that usually escapes during computer processing. Therefore, the strategy for improving the methods for obtaining thematic information from aerospace images is to integrate visual and computer interpretation, each of which has its own advantages and limitations. Thus, the visual interpretation of images on a computer screen is successfully supplemented by automated processing using special programs that improve the decoding properties of the image, or quickly and with great detail to select clearly depicted objects. To separate objects of different types, to determine the boundaries between them, methods of computer classification (clustering) are used. The computer makes it possible to analyze large amounts of digital information, which is necessary, for example, when processing hyperspectral images. It is noteworthy that in order to judge the reliability of the results of computer processing of images, it is often necessary to use visual assessments.

№34 Quantitative, instrumental, automated and automatic decoding. Difficulties of computer decoding.

The results of visual interpretation are often subjective, so it is important to objectify this method of obtaining information by introducing measure and number into it. When using observational and measuring instruments, one speaks of instrumental and measuring decryption; if the result of decoding is obtained on the basis of the numerical characteristics of the image, then decoding is called quantitative. We have always strived to automate the heuristic process of deciphering in general, therefore, in the textbooks on the discipline, there are terms - automated and even completely automatic decoding, which rightfully belongs to the fundamental scientific direction - pattern recognition.

With the spread of personal computers, decryption began to be more often divided into visual, in which, as before, the result is achieved by a person using his visual system and intellect, and computer, when it is entrusted (as a rule, partially) to an electronic computer.

The task of computer interpretation of images is reduced to classification - sequential "sorting" of all pixels of a digital image into several groups.

For this, two types of classification algorithms are proposed - with and without training (clustering - from the English "cluster, group").

When classifying with training, the pixels of a multi-zone image are grouped based on a comparison of their brightness in each spectral zone with reference values.

When clustering, all pixels are divided into cluster groups according to some formal feature, without resorting to training data. Then the clusters obtained as a result of automatic grouping of pixels are assigned by the decoder to certain objects.

Disadvantage of the method:

* the results are not always objective (reliability is only 60-80%);

* the method is not entirely independent (often helps and complements the performer).

№35 Image resolution and spatial resolution.

To characterize the detail of aerospace images, several quantitative indicators have been proposed. Among decoders, two indicators are most widely used: spatial resolution and resolution, which is used to evaluate photographic materials.

Resolution.– the possibility of separate reproduction by a layer of small closely spaced image details . It is determined by the photographic image of a special standard test object - worlds. The dashed world consists of elements with a different number of strokes per linear millimeter. The strokes of the worlds are made absolutely white and absolutely black, i.e. their visual contrast Kv = 1. Currently, millimeters to the minus first degree (mm-1) are accepted as the unit of measurement. When they say

that the photographic material has a resolution of 50 lines per millimeter (50 mm-1), this means that it can separately reproduce 50 black strokes with a width of 0.01 mm and 50 white strokes on one running millimeter.

Resolution:

Aerial photos (10-40mm^-1)

Space (in 2-3r. above)

Spatial resolution is a value that characterizes the size of the smallest objects distinguishable in the image.

№36 Comparative interpretation. Deciphering multi-temporal images. Field and cameral interpretation. Reference decoding. Indication.

Comparative deciphering - is based on the use of spectral images of objects depicted in the image. The spectral image of an object in a photographic image is determined visually by the tone of its image in a series of zonal black-and-white images. Based on the obtained data, a curve of the spectral image is constructed, which reflects the change in the optical density of the image in the images in different spectral zones. In this case, the values ​​of the optical density of prints plotted along the ordinate axis D, up the axis decrease so that the spectral image curve matches the spectral brightness curve. Comparative decryption scheme: determination of the spectral image of the object from images - comparison with the known spectral reflectivity - identification of the object.

On each of the zonal images, certain sets of objects are separated by image tone, and these sets are different on images in different zones. Comparison of zonal images allows you to separate these sets and highlight individual objects, in this case. Such a comparison can be implemented by combining ("subtracting") the schemes for deciphering zonal images, each of which identifies different sets of objects.

Deciphering multi-temporal images. Multi-temporal images provide a qualitative study of changes in the objects under study and indirect interpretation of objects by their dynamic features.

Dynamics research. To identify changes in multi-temporal images, they must be compared with each other, which is carried out by alternate (separate) or simultaneous (joint) observation. Technically, the visual comparison of multi-temporal images is carried out most simply by observing them one by one. A very old way of "blinking" (flicker-method) allows you to simply detect a newly appeared separate object by quickly viewing two images at different times in turn. From a series of shots of a changing object, an illustrative cinegram can be assembled. So, for example, if images of the Earth obtained in 0.5 hours from geostationary satellites in the same angle are assembled into an animation file, then it is possible to repeatedly reproduce the daily development of clouds on the screen.

To identify small changes, it turns out to be more effective not sequentially, but joint observation of multi-temporal images, for which special techniques are used:

combination of images (monocular (through the light) and binocular (each image is viewed with one eye, using a stereoscope)); stereoscopic observations (used in the study of changes due to movement, movement of objects).

Decoding by dynamic features. Patterns of temporal changes in geographical objects, which are characterized by a change in states over time, can serve as their deciphering features, which are called the temporary image of the object. For example, thermal images taken in different time days, allow you to recognize objects that have a specific daily temperature variation.

Field and cameral interpretation. At field In deciphering, identification of objects is carried out directly on the ground by comparing the object in kind with its image in the photograph. Additional shooting is carried out by eye or instrumental method. For this, satellite positioning receivers are used, which make it possible to determine in the field the coordinates of objects that are absent in the image, with almost any required accuracy.

At cameral decoding, which is the main and most common type of decoding, the object is recognized by direct and indirect deciphering features without entering the field and directly comparing the image with the object. In practice, both types of decryption are usually combined.

Reference decoding. Cameral interpretation is based on the use decryption standards created in the field on key areas typical for the given territory. Thus, deciphering standards are pictures of characteristic areas with the results of deciphering typical objects printed on them, accompanied by a characteristic of deciphering features. Further, the standards are used in cameral interpretation, which is performed by the method of geographical interpolation and extrapolation, i.e., by spreading the identified deciphering features to the areas between the standards and beyond.

At Indicative decoding define not the object itself, which may not be displayed in the picture, but its pointer, indicator. Vegetation cover, as well as topography and hydrography, are most often used as an indicator. Indirect signs underlie landscape a deciphering method based on multilateral links between individual components of the landscape, between the deciphered object and the entire natural complex.

Example: Vegetation can also be used to judge soils and soils; mass objects often serve as indicators of the movement of water masses in the ocean, near-surface winds, and ice of glaciers. (tracers), collectively visualizing direction and character

movement. Their role can be played by broken ice, phytoplankton, pattern of cracks or layering on the surface of a mountain glacier.

During indicative deciphering, they make up the so-called indicator tables, where for each type or state of the indicator, the type of the displayed object corresponding to it is indicated.

№37 Features of observing pictures on the display screen. Instruments and aids. Formulation of decryption results.

Features of observing images on a computer screen. The characteristics of the display screen are important for the perception of images: the best interpretation results are achieved on large screens that reproduce the maximum number of colors and have a high image refresh rate. Enlargement of a digital image on a computer screen is close to optimal in those cases where one pixel of the image corresponds to one pixel of the screen.

The time of effective work when deciphering screen shots is shorter than when deciphering visual prints. It is also necessary to take into account the current sanitary standards for working on a computer, which regulate, in particular, the minimum distance of the decoder's eyes from the screen (at least 500 mm), the duration continuous work, intensity of electromagnetic fields, noise, etc.

Instruments and aids. Often in the process of visual interpretation, it is necessary to make simple measurements and quantitative estimates. To do this, various kinds of auxiliary tools are used: palettes, scales and tables of tones, nomograms, etc. For stereoscopic viewing of images, stereoscopes of various designs are used. The best device for cameral interpretation, a stereoscope with a double observation system should be considered. The transfer of interpretation results from individual images to a common cartographic basis is usually performed using a small special optical-mechanical device.

Formulation of decryption results. The results of visual interpretation are most often presented in graphic, textual and less often digital forms. Usually, as a result of deciphering work, a snapshot is obtained in which the objects under study are graphically highlighted and indicated by conventional signs. When working on a computer, it is convenient to present the results in the form of printer prints. Based on satellite images, so-called decryption schemes, which, in their content, represent fragments of thematic maps compiled to the scale and projection of the image.

№38 Two technological schemes visual interpretation. Decryption steps.

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

2) identification of a set of decryption objects (drawing up a preliminary legend for a future decryption scheme or map);

3) selection of images for interpretation, transformation of images to increase their expressiveness, preparation of instruments and aids decryption. It should be borne in mind that images that are optimal for solving one problem may not be effective for another;

4) actual interpretation of aerospace images and assessment of its reliability;

5) registration of the results of decoding.

The central point of any work is the actual interpretation of aerospace images. Thematic interpretation can be performed according to two principal logical schemes. The first scheme provides for object recognition first, and then their graphical selection; the second scheme - first, graphical selection in the image of areas with the same type of image, and then their recognition. Both schemes end with the stage of interpretation, the scientific interpretation of the results of deciphering. Working with images, especially with space ones, the decoder is widely attracted additional material, usually cartographic, which serves to clarify the deciphering features and evaluate the deciphering results.

The first scheme turns out to be universal for solving most problems; it has received wide recognition in the practice of visual interpretation. The second scheme is very effective in deciphering relatively simple objects by brightness features, but has limited application. Both of these schemes in computer interpretation are implemented in classification technologies with and without training.

No. 39 Deciphering signs. Direct and indirect (shape, size, tone, color, shadow). Image drawing (texture, structure).

On an aerospace image, objects differ from one another in a number of deciphering features. Identify the main features, which are usually divided into straight (simple and complex) and indirect . Direct simple deciphering features are the shape, size, tone (color) of the image and shadow, and a complex (complex) feature that combines the above features is the image pattern. Indirect signs are based on relationships between objects, on the possibility of identifying objects that are not visible in the image by other objects that are well depicted. Indirect signs are also the location of the object, geographical proximity, traces of the impact of the object on the environment.

Each object has its own characteristics, which are manifested in direct and indirect deciphering signs, which are generally not constant, but depend on the season, time and spectral ranges of the survey, image scale, etc. A novice performer works more with direct deciphering features; the skillful use of indirect signs is evidence of the high qualification of the decoder.

At direct deciphering uses direct signs.

The form - effective direct sign in visual interpretation. It is in the shape of the contour that the main part of the information about the object is contained. Anthropogenic objects have a geometrically correct, standard form- agricultural fields are distinguished in a rectangular shape.

The size - a feature used mainly when working with large-scale images. Buildings of various functional purposes are distinguished by size. , separate the fields of grain and fodder crop rotations.

Tone image, determined by the brightness of the object and the spectral area of ​​the shooting, helps to separate the main types of surface: snow, open ground, vegetation.

Color - a more informative and reliable feature than the tone of a black and white image. Water bodies, forests, meadows, plowed fields are well distinguished by color. Using images with purposefully distorted colors, separate different types of vegetation, rocks etc.

Shadow can be attributed to both direct and indirect deciphering features. The shadow on detailed images reflects the silhouette of the captured object and allows you to estimate its height. Since the shadow always has a relative contrast that is much greater than the object itself, it is often only the falling shadow that makes it possible to detect objects that are small in plan, but tall, such as factory chimneys. In mountainous regions, deep shadows make it difficult to decipher. Shadows significantly affect the drawing of the image.

picture drawing- a stable complex decoding feature that provides unmistakable identification of not only such objects as agricultural fields, settlements, but also different types of geosystems. Each natural-territorial complex is characterized by a certain pattern in the image, which reflects its morphological structure. In the figure, the images are distinguished texture - the shape of the pattern-forming elements and structure - spatial arrangement of texture elements. Sometimes the pattern of the image is characterized by quantitative indicators, which serves as the basis for morphometric interpretation.

No. 40 Characteristics of computer systems for image processing ( Hardware, software, screen rendering and printing of images).

Performance, Video memory size, Software. The following basic requirements are imposed on software packages for computer image processing: versatility visualization capability programmability: integration: General-purpose software is also used: for image visualization, simple processing and preparation for printing - graphic editing programs (Adobe Photoshop, Corel PHOTO-PAINT) , for creating descriptions and reports - text editors (MS Word, Word Perfect), for quantitative analysis images - programs for statistical data processing (MS Excel), for viewing and receiving images via the Internet - network programs (MS Internet Explorer, Netscape

Hardware. The main components of a computer include: central processing unit(CPU); RAM(OP) that stores data and programs used by a computer in this moment work; HDD for permanent storage of data and programs; managers controllers various external devices for input, output and presentation of information - disk drives, monitor, printer, scanner, devices for reading and writing magnetic tapes, audio playback devices, digital cameras, PDAs, global satellite positioning receivers (GLONASS / GPS), etc. .

For image processing, the following interrelated computer parameters are most important:

performance, disk space and random access memory, the amount of video memory.

Screen visualization and printer printing of images. Experience shows that for a comfortable visual interpretation of a picture on the screen, it is important to use a screen with a diagonal size of at least 17 inches (43 cm), with a screen matrix of at least 1024x768 pixels.

Since the results of computer processing are often presented on paper, the way in which printer prints of images are made is important. For this, it is used laser and jet seal. With the more common inkjet technology, an image is created using a printer's print head, from which microscopic droplets of multi-colored ink are sprayed onto the paper.

When making printer prints, keep in mind that the colors of the print will always differ from the color gamut of the screen shot. Therefore, mutual calibration of the printer and the monitor screen is necessary, for which there are special computer programs. Another important parameter is the resolution of the printer, traditionally measured in dpi. For high-quality image reproduction, a resolution of at least 600 dpi is required.

Software divided into operating systems and application programs. The former ensure the operation of the computer as a whole and basic functions: accessing files, launching application programs, managing the order in which various programs access external devices, such as a hard drive and a printer.

The following basic requirements are imposed on software packages for computer processing of images:

a) universality;

b) the possibility of visualization;

c) programmability;

d) integration;

№ 41Trends in the development of hardware, software and information support.

Personal computers are rapidly improving, expanding the possibilities of image processing. The speed of processors is increasing, their number is growing, the amount of disk and RAM is growing; practiced distributed processing of images on several computers through the use of local networks and the Internet; increasing the size of the screens and improving their quality; computer facilities are being expanded for the use of stereo images and virtual three-dimensional models in the process of deciphering. In the future, voice control of programs is possible instead of manually entering commands. The volume of publicly available reference digital information is increasing, for example, libraries of reference values ​​of the spectral characteristics of various objects on the earth's surface; new digital topographic and thematic maps appear for different regions of the Earth. Data processing algorithms are being improved and semi-automatic interactive expert systems are being developed for deciphering images based on a knowledge base - a set of decision rules and a reference database.

№ 42 Digital image storage formats. Compression - decompression of information.

Storage formats for digital images. The format in which the snapshot file is stored is how it is written for storage on a storage medium (hard disk, floppy disk, CD-ROM).

Exists big variety raster graphic formats for storing various images that are also used for snapshots, such as TIFF, BMP (lossless), JPEG, GIF (lossy). There is no single generally accepted format for storing aerospace images.

Most software packages for computer image processing provide reading of the most common raster formats and translation from one format to another.

Digital Image Compression(“packing”, “compression”) is a transformation aimed at compacting information, at reducing its volume, expressed in bits or bytes. This is necessary to save the memory required for recording and storing images when transmitting them from satellites to Earth via space communication channels with a small bandwidth, as well as to compress excessively detailed images, which allows them to be processed faster on a computer or transmitted over the Internet.

Compression is combined with decompression("unpacking") - restoring the original image. Compression can be performed without loss and with loss of information. If the image contains solid-color objects that are displayed by pixels with the same brightness value, for example, clean water bodies, then compression without loss of information is carried out by replacing repeated the same values brightness with one value indicating the number of such pixels. Experience shows that with this type of compression, the amount of information in aerospace images is on average reduced by a factor of two, but the image can be completely restored during decompression. Typically, lossless compression is carried out using the TIFF format, which is widely used for recording images. In lossy compression, the brightness values ​​of pixels of the same type of areas, such as forest plantations, varying within certain limits are averaged, and then this average value and the number of pixels are recorded for all pixels. In this case, the amount of information in the aerospace image can be reduced tenfold, but the image details are no longer restored during decompression. This compresses the image in the JPEG format, which is used for making viewing space images on the Internet.

№ 43Analysis of modern sources of aerospace information. Google Earth, SASPlanet.

Google professional tool for processing, analysis and visualization of geodata. The program combines a huge number of satellite photographs, which makes up a complete map of the Earth. Virtually the entire surface of the land is covered with images obtained from DigitalGlobe, with a resolution of 15 meters per pixel. There are separate areas of the surface (usually covering the capitals and some big cities most countries of the world) with a more detailed resolution. For example, Moscow was filmed with a resolution of 0.6 m/pixel, and many US cities with a resolution of 0.15 m/pixel. Landscape data has a resolution of about 100 m. SAS.Planet / SAS.Planet / SASPlanet is a free program designed to view and download satellite images high definition and ordinary cards? all the maps you download will remain on your computer and you will be able to view them even without an internet connection. In addition to satellite maps, it is possible to work with political, landscape, combined maps, as well as a map of the Moon and Mars. Loading maps is carried out both by selecting a certain area (possibly non-rectangular), and in the process of moving around the map. Maps are updated frequently - the program will only allow you to download the newest ones.