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An aerial photograph is theoretically and practically sharply different from a map, for example, in outward appearance... At the same time, the map and the aerial photograph have much in common, since both of these documents are an image of the area. This image, both on the map and on the aerial photograph, was obtained at a certain scale, which is characterized by the dimensions of the images of certain topographic objects.
The essential difference between an aerial photograph and a topographic map follows from the geometric essence of their acquisition.
Topographic map is an orthogonal projection of the terrain (Fig. 99, a), i.e. a projection in which the image of terrain objects on a plane is obtained using projection rays perpendicular to the projection plane.
Rice. 99. Projection: a) orthogonal; b) central
An orthographic projection is characterized by two basic properties: the distances on the map are proportional to the horizontal distances of the corresponding distances on the ground; the corners with the vertices at any point on the map are equal to the corresponding horizontal angles on the terrain.
Unlike a map on aerial photographs, the image of terrain objects is constructed by projecting rays intersecting in the lens of an aerial camera.
A projection in which the image of objects on a plane is obtained using projection rays intersecting at one point is called central (Fig. 99, b), and the point of intersection of these rays is the center of the projection. Therefore, the aerial image is the central projection of the terrain.
Lecture 17. Photo-topographic surveys (continued)
17.1. Summer shooting
17.2. Aerial view scale
17.3. Displacement of a point in the image due to the relief
17.4. Transforming aerial photographs
17.5. Concentration of plans - high-altitude justification of aerial photography
17.6 Decoding aerial photographs
17.7 Creation of topographic maps from aerial photographs
17.8. Questions for self-control
Summer shooting works
As a rule, aerial photography is performed at a smaller scale compared to the given scale of the produced map or plan.
Aerial photography is performed so that the longitudinal overlap is not less than 60%, and the transverse overlap is not less than 40%.
To ensure the specified amount of overlap, it is necessary to observe the photography basis. Basis photographing is the distance that an aircraft flies between two adjacent photographing points. The photography basis is calculated by the formulas:
,
,
- longitudinal basis of photographing along the route;
- the distance between the axes of two adjacent routes;
- dimensions of the longitudinal and transverse sides of the aerial photograph;
Is the denominator of the scale of aerial photography.
To facilitate aircraft driving and entering it from route to route, landmarks that are clearly visible from the air are outlined in advance on the map.
After the aerial photography, the filmed cassettes are processed, and aerial photographs are made from the negatives obtained after the development and fixation by contact printing.
To check summer survey work, a block installation is performed, which is an approximate combination of aerial photographs along their contours of the same name into one continuous picture of a covered area.
The quality assessment of the summer survey is carried out according to the following criteria:
1) the quality of the photographic image;
2) the size of the longitudinal and transverse overlap;
3) deviation of the camera axis from the vertical;
4) straightness of the route;
5) deviation from the given flight altitude of the aircraft.
The identified disadvantages of aerial photography are eliminated. The block montage is photographed on a small scale - a reproduction of the block cut is obtained. It is used for preliminary study of the area.
Aerial view scale
An aerial photograph of a horizontal section of flat terrain, obtained with the vertical position of the optical axis of the AFA, is a contour plan of this terrain suitable for various measurements.
Rice. 100. Scale of horizontal aerial photograph
The scale of such an aerial photograph (Fig. 100) is called horizontal, expressed by the ratio
,
where m- the denominator of the numerical scale of the aerial photograph; oa- segment in the picture; OA- section on the ground; f k- focal length AFA; H Is the flight altitude of the aircraft.
If the optical axis deviates from the vertical position, then the resulting aerial photograph will have a different scale at each point. In this case, we can only talk about the average scale of the image.
In the middle of the 19th century, the capital of France, the city of Paris, rose Balloon, and photographer Nadar photographed the city from a bird's eye view for the first time. The Parisians saw how the city blocks, streets, the Seine River, on the banks of which the city grew up, looked like from above. This is how the first aerial photographs appeared - reduced photographic images of an area of the earth's surface (er - in French for "air").
Currently, aerial photographs are taken from aircraft and unmanned aerial vehicles, including multicopters.
The aerial photograph shows houses, roads, bridges, rivers and ravines, fields and forests - in short, everything that we see on the plan and map. Learning to recognize geographic objects in an image is a cheat to learn decrypt aerial photograph. Not only objects are important, but also the tone of the image: the more humid and damp the earth, the darker the tone of the image. The water in the river or lake will be completely dark in the picture. It is impossible to see on the map whether the soil is wet on the field or not. Yes, this is not required, in a few days the soil on the field may dry out.
If the plane is flying high above the ground, then the scale of the aerial photograph is small. If the plane is flying low, the aerial photograph will have a large scale, a small area will be visible on it with great detail. During aerial photography, the plane flies in a given direction and takes pictures at regular intervals. Then it turns around and flies back parallel to the recent path, again photographing the ground. Neighboring aerial photographs are glued together and, using them, a plan or map is drawn.
A map is a reduced generalized image of the earth's surface. For the image on the map, they select the most important, the most significant, that which will not change in a week. The names of the rivers are inscribed on the map, settlements, the main roads, the plans show both the direction of the river flow, and the nature of the road - asphalt, unpaved, etc. Material from the site
The globe accurately reflects the landforms of the Earth, but it is not always convenient to use it. It is more practical to give an ob-drawing of the Earth and its parts on a plane, on paper.
Let us consider in the atlas the image of the Earth's surface - a drawing and a plan of the area (Fig. 14, 15), aerial photographs (Fig. 16), a satellite image (Fig. 17) and a geographic map (Fig. 18). How do they differ from each other?
Aerial view - This is a photograph of the area, which is taken from an airplane or other aircraft using a special aerial camera in the appropriate scale.
Aerial photography is used during geographical and geological research, engineering prospecting, and also in the preparation of topographic maps.
Space shot - This is a photograph of the earth's surface or the entire planet, which is made by automatic photographic equipment from artificial earth satellites.
Space images made it possible to compile a new type of maps (cosmophoto maps). On their basis, such a branch of science as space cartography is developing. In particular, there is detailed maps Moon, Venus, Mercury, Mars. On the terrain plan, all objects and objects are reproduced with generally accepted conventional signs.
Site plan - this is an image of a small area of terrain using conventional symbols and to scale.
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| Rice. 16. Aerial view of the area |
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| Rice. 17. Space shot |
On a geographic map, as well as on a plan of the area, objects are also shown with conventional symbols.
Geographic map - This is an image of the required territory or the entire planet using conventional signs and on a certain scale.
The set of conventional signs and their explanations are called legend card... All types of conventional signs are divided into contour, off-scale, linear. Outline signs transmit the actual dimensions of the object, consist of a path filled with color or hatching. For example, a forest, a swamp, a lake - on the terrain plan, mountains, plains, continental contours - on a geographic map . Out-of-scale signs as geometric shapes, symbols, drawings show objects that cannot be indicated on the scale of a plan or map. For example, a spring, a well, a school on the terrain plan, signs of minerals and settlements, mountain peaks . Linear signs transfer linear objects on the plan and map: roads, rivers, borders, etc. The scale shows only their length, but not their width. Depending on the size of the displayed area and the size of the map itself, different scales are used. The smaller the territory and the more details in its reproduction, the larger the scale of the map. It is called large-scale... Plans of the area have such a scale (1: 5000 and more). There are also large-scale topographic maps(from 1: 5000 to 1: 200000) (fig. 19). In fig. 19 - the scale is larger, and in Fig. 18 - less. Such maps depict a small area in detail. They are used in military affairs, construction, when laying roads, in agriculture, hiking trips, etc. Maps with a scale from 1: 200,000 to 1: 1,000,000 are called medium-scale(fig. 20).
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| Rice. 18. Physical map |
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| Rice. 19. Topographic map (scale 1: 10,000) |
But most often a person needs to show on a map huge territories of the continents, individual countries or their regions, and sometimes the entire planet. Then they use a small scale, and the maps are called small-scale(fig. 21). School atlases maps, wall maps - small-scale. For example, the scale of the map of the hemispheres in the school atlas is 1:90 000 000 (in 1 cm - 900 km), maps of Ukraine - 1: 6 000 000 (in 1 cm - 60 km). Please note that the scale of the first map is smaller, and the second is larger.
It is impossible to show all the smallest objects on the ground on the plan and on the map. They would get in the way of reading the images. Therefore, only the main ones are applied to the plan and map, i.e. image generalize. The smaller the scale of the map, the greater the generalization. Material from the site
Plan and map Is a scaled-down image of the earth's surface on a plane.
Geographic maps depicting natural objects (continents, oceans, mountains, plains, rivers, lakes, etc.) are called physical... For instance, physical map hemispheres, physical map of Ukraine.
There are several types of images of the Earth or its individual areas: a globe, a plan of the area, geographic map, drawing, aerial photograph, space image.
On this page material on topics:
More precisely, a physical map or aerial photograph
Aerial view and map
How an aerial photograph differs from a plan
How photographs from space differ from aerial photographs
What is the difference between an aerial image and a satellite image
Questions about this material:
Lesson:What is a site plan
1. Introduction
The purpose of the lesson: to find out what types of terrain images are, what a terrain plan is.
2. Types of images of the earth's surface
Before making a decision on the construction of new factories, schools, sports facilities, on the construction of roads, on the placement of agricultural land, it is necessary to have an image of the area.
A small area can be drawn or photographed, but many objects on the earth's surface from such images will be difficult to identify.
The most common images of the earth's surface are aerial photographs, satellite imagery, maps and ground plans.
Rice. 1. Aerial view
3. Aerial photographs and plans of the area: similarities and differences
Plan -drawing of a reduced image of the area, made in conventional signs on a large scale (usually 1: 5000 and larger). Usually, plans are made for a small area of terrain, several square kilometers in size, the curvature of the Earth's surface is not taken into account. The first maps in history were plans. The plans are used in a wide variety of industries and agriculture. When constructing buildings, laying roads and communications, you cannot do without them.
Objects placed on the surface (forests, rivers, villages, fields, etc.) will be seen better if the site is photographed from above, for example, from an airplane. Such an image of the area is called an aerial photograph. On it, objects are similar to their true appearance on the ground, their sizes are visible and mutual arrangement... There are many differences between a plan and an aerial photograph. A site plan is a drawing on paper showing small area the earth's surface in a reduced form. The plan differs from other images of the surface in that all objects on it are shown with conventional signs. In general, it is more convenient and informative to use the plan.
Aerial view and site plan:
Rice. 2. Aerial photograph and plan of the area
4. Site plan. Symbols
Directions on the plan are indicated by an arrow, the tip of which always points north. Usually, north on the plan is at the top, south - at the bottom, east - on the right, west - on the left. According to the plan, you can determine the relative position of objects on the sides of the horizon, measure the distance between them using a single scale.
Rice. 3. Site plan
Rice. 4. Site plan and conventional signs to it
The conventional signs of the plan, firstly, are simple, secondly, they are unlike each other, and thirdly, they resemble the objects themselves. Under such conditions, they are understandable to everyone who reads the plan. So, rivers and lakes are shown in blue water, and forests - in green - the color of vegetation. For fields, vegetable gardens special sign no, therefore such areas are left white on the plan. The sign of the meadows resembles the stalks of grass. The sands are shown with brown dots. Small streams, roads, narrow streets are depicted with conventional signs in the form of lines. Such symbols are generally accepted. They are used on all plans of the area.
Rice. 5. Symbols
Symbols groups:
1. Areal
Aerial photography Aerial photography - a set of works for obtaining topographic plans, maps and DTM using materials for photographing the area from aircraft or from space. Aerial survey materials are the basis for drawing up tablets, plans, schematic maps and other graphic documents that serve to solve operational problems and to plan long-term activities in forestry. Types of aerial photography (by design features AFA) 1. Personnel (a series of individual frames); 2. Slit (slit image - in the form of a continuous "tape" along the route 3. Panoramic (rectangular images with a large transverse angle of view) (along the flight altitude of the aircraft) 1. Space photography of the earth's surface (the first hundreds of kilometers) is carried out from artificial earth satellites 2. Aerial photography (AFS) is performed from aircraft and helicopters: 2 a - high-altitude (5-10 km). 2 b - standard (1-5 km). 2 c - low-altitude (m)
(on the use of spectrum zones) 1. Color - images are obtained in natural colors of the area; 2. Black and white — Pictures are taken in grayscale. This allows you to remove the excessive variegation of the image of the territory, while maintaining the phototone - the intensity gray and textures of the image. 3. Spectrozonal - with the help of filters, images of certain parts of the spectrum are obtained and painted in conventional colors. The technology allows you to combine and combine images of individual parts of the visible spectrum. 4. Radar - receiving images from radio waves reflected from a point of the terrain - all-weather shooting. 5. Infrared (thermal) - using thermal imagers. 6. Multi-zone - several cameras working simultaneously. (by the way of work organization) 1. Route. A kind of planned shooting. Produced along certain directions, river valleys, mountain roads, etc. 2. Areal (multi-line) - the main type of survey when surveying areal and linear objects. 3. Combined. Combination of AFS with one of the types of land-based topographic survey ..
(according to the position of the optical axis AFA) 1. Planned. Photographing is carried out in the vertical direction, from top to bottom, with a deviation from the vertical no more than 3º. This type of shooting covers large areas, flying over it with tacks (overflights). Typically, flights are latitudinal. This is the most commonly used type of photography. I-1 I-2 I-4 I-6 I-7 I-8
Planned-high-altitude justification of aerial photography The planned position of the contour points is determined in office conditions by phototriangulation. On the ground, during field ground geodetic works, the coordinates of the corresponding number of terrain points required to create a triangulation are determined. An identification mark is a contour point of an aerial photograph, the coordinates of which are determined on the ground as a result of binding to points of the GGS. Planned landmarks are combined with clear, easily recognizable terrain contours on an aerial photograph. The location of the marks is carefully determined and pinned on the aerial photograph.
AERIAL PHOTOGRAPHY EQUIPMENT AERIAL PROCESS Aerial photographic installation - attachment of AFA to the body of the aircraft; cushions the camera. Control (command) device: remote control and control over the work of AFA. Navigation equipment (radio or laser altimeter: detects flight altitude; statoscope: detects fluctuations in flight altitude). The aerial photography process includes: Preparatory work: determination of objects and timing of the APS. Flight shooting: photographing from an aircraft at a favorable time for filming. Photolaboratory work consists in developing aerofilms and obtaining aerial photographs and transparencies on their basis.
Block montage of aerial photographs is obtained by superimposing them on top of each other with overlapping parts. A reproduction of a block layout is a copy of a block layout on photographic paper. With the help of block mounting, the quality of flight-survey works is assessed. Determine: - the deviation of the actual longitudinal and transverse mutual overlap of adjacent aerial photographs from the permissible values (permissible minimum overlap: 35% for the longitudinal and 15% for the transverse); - invariability of photographing altitude (permissible changes in flight altitude - up to 5%); - straightness of the route (permissible deviations of the route from the straight line - no more than 3% of its total length).
AERIAL PHOTOS An aerial photograph is a central projection of a terrain, which is formed by a bunch of projectors, formed by a bunch of projecting rays. rays. The point of intersection of the optical axis of the aerial camera with the plane of the photosensitive layer (O) is called the main point and is taken as the origin of the rectangular coordinate system of the image. S - projection center (rear nodal point of the aerial camera); Aa, Be, Oo, Cc. Dd - light rays; Aa, Be, Oo, Cc. Dd - light rays;
О - main point of the image; So = t is the focal length of the AFA lens; SO - photography height; oh, in. o, c, d - image on the photosensitive layer. A projection in which the image of objects on the plane of objects on the plane is obtained using projection rays intersecting at one point is called central, and the point of intersection of these rays is the center of the projection.
AFS overlap An aerial overlap is a "common" part of the earth's surface shown in two adjacent images. During the flight, the overlap should be at least 60%, for neighboring flights - 15% (GOST) Scale of the APS Limitation is imposed by the resolution of the eye (0.1–0.2 mm). Therefore, to solve different tasks use APIs of different scales. According to the standards, the scale of the API used should be at least 2 times larger scale works. 1. Regional tasks - mb AFS 1: - 1: (space photography). 2. Medium-scale geological survey - mb AFS 1: - 1: (high-altitude and standard aerial photography). 3. Large-scale and detailed geological survey - mb AFS 1: - 1: (low-altitude aerial photography).
Image geometry 1. Working part and image fields. In the fields (1 a), put the number of the picture and additional information (order number, date and time of shooting, bubble level). 2. Main point of the picture. An image of the point on the surface where the optical axis of the camera is aimed. 3. Coordinate vertices of the image. Markers to help you set the main point of the image. 4. Basis of the snapshot. Distance between the main point of the current image and the position of the main point of the previous image on it. 5. Point nadir. A snapshot image of a point on the surface of the earth exactly below the plane. 6. Direction of shooting. A line through the main point and the nadir point. The plane cannot fly absolutely smoothly, the winds twist it as they want, i.e. at the time of shooting, the plane is always tilted to one degree or another: roll pitch
Distortions on the APS 1. Distortions associated with variability of scale The image is a central projection, and not a plan one, like a map. The standard image scale is 1 / M = f / H, where f is the focal length of the camera, H is the shooting height above the terrain. Obviously, SA = SB> H, therefore M H H, therefore M H 
2. Distortion due to the tilt of the aircraft. The scale of objects A and B is the same. Ideally, i.e. when the plane is perfectly horizontal and oriented strictly on the course, the center point of the image (o) coincides with the nadir point (n). In a real flight, this does not happen, so the central point of the image "walks" around the nadir point. pitching up diving When pitching, the aircraft either lifts up the nose (pitching) or lowers it (dives). When pitching up, the center point "goes" forward from the nadir point, due to which the scale of the part of the APS located along the flight becomes smaller. When diving, the central point "goes back" from the nadir point, due to which the scale of the part of the AFS located along the flight becomes larger. n, o n о n о BA Scale of object B is smaller than the scale of object A B A B A Scale of object B is larger than the scale of object A
The scale of objects A and B is the same. The left roll is smaller than the right roll. During roll, the plane sways about the longitudinal axis (shakes its wings). With a left roll, the central point "leaves" to the right of the nadir point, due to which the scale of the part of the AFS located to the right in flight becomes smaller. With the right bank, the opposite is true. n, o n о n о BA Scale of object B is smaller than the scale of object A B A B A Scale of object B is larger than the scale of object A During yaw, the angle between the longitudinal axis of the aircraft and the direction of flight changes. This does not lead to additional distortions of the scale, within the same image, however, the overlap zone becomes trapezoidal, which complicates further interpretation.
3. Distortions associated with the relief When photographing an area with a dissected relief, different points are at a varying distance from the center of the projection, which leads to image distortion in comparison with the planned projection. Points located on higher elevations in the image "move away" farther from the main point of the image, and those located in lower areas - "approach" it. At the same time, of course, the scale is also distorted: objects on higher elevations look larger, objects in lowlands - smaller. r - displacement on the image to the position on the planned projection (correction), r - distance from the point to the main point of the image, H - average survey height over the terrain, h - point elevation above the average terrain height.
ELEMENTS OF IMAGE ORIENTATION Orientation elements of an aerial photograph are values that determine its position at the moment of photographing relative to the selected spatial rectangular coordinate system. There are elements of internal and external orientation of the image.
ELEMENTS OF INTERNAL ORIENTATION OF AEROPHOTOS. Three elements of interior orientation - the focal length of the camera f, the coordinates x 0, y 0 of the main point o. They define the position of the center of the projection relative to the aerial photograph. S f y o o "x y0y0 x0x0
ELEMENTS OF EXTERNAL ORIENTATION OF AERO PHOTOS The elements of external orientation allow you to set the position of the image (link), which it occupied at the time of photographing relative to a given spatial rectangular coordinate system. For AFA images, two such systems are used in practice. Fig. 1 Fig. 2
The first EVO system (Fig. 1) includes the coordinates Xs, Ys, Zs of the photographing point, as well as the angles of rotation of the image α, ω and κ. The longitudinal angle α of the image is formed by the Z΄ axis and the projection of the main ray Sо onto the X΄ Z΄ plane. The transverse tilt angle ω of the image is between the main ray Sо and its projection onto the X΄ Z΄ plane. The image rotation angle κ form the y-axis of the image and the trace of the plane passing through the main ray Sо and the Y΄ axis (the angle ω is located in this plane). In fig. 1, the angles κ and ω are positive, the angle α is negative. The second system (Fig. 2) EVO contains: coordinates Xs, Ys, Zs of the photographing point; t is the directional angle of the optical axis of the camera - it is formed by the trace of the plane of the main vertical W and the positive direction of the X΄ axis; ε - tilt angle of the image, located in the plane of the main vertical between the main and nadir rays; κ - angle of rotation in the image plane, formed by the main vertical and the y-axis of the plane coordinate system x y.
BASICS OF STEOPHOTOGRAMMETRY The main task of photogrammetry in its application for topography is to determine the coordinates of points in the area from aerial photographs. Using a single aerial photograph, it is possible to determine only the planned position of the points displayed on it. To determine the heights of points of the terrain, it is necessary to have two aerial photographs of a given area, obtained from two different points or from two ends of the photographing base. Two images with images of the same area, obtained from two points in space, having an overlap of at least 55%, are called a stereoscopic pair of images (stereopair). The picture taken from the point of photographing S 1 is called left, and with S 2 - right.
In fig. depicts a couple of shots in the position that she was at the time of photographing. A - a point of the terrain, depicted on the images at points a 1 and a 2. They are called the corresponding points or points of the same name. The projection rays S 1 A and S 2 A passing through these points are called the corresponding or projection rays of the same name. A a1a1 a2a2 A S1S1 S2S2 S 2 a 2 W1W1 W2W2 bпbп
The distance B between the photographing points S 1 and S 2 is the photographing basis. The plane W A passing through the datum and point A of the terrain is the datum plane. The planes passing through the photographing base and the main rays are the main base planes (W 1 - left W 2 - right pictures). Any pair of corresponding beams intersect if the pictures occupy the position that was at the time of photographing. The collection of their intersection points forms a surface. It is called a stereo model or simply a terrain model. If one of the bundles (for example, the right one) moves translationally along the basis from position S 2 to S 2, the clothing will not collapse, but its scale will change. The distance b p between the centers of the projections of the two sheaves along which the model is built is called the design basis. If one of the bundles (for example, the right one) moves translationally along the basis from position S 2 to S 2, then the model will not collapse, but its scale will change. The distance b p between the centers of the projections of the two sheaves along which the model is built is called the design basis. Its scale is calculated by the formula: i / t = b n B i / t = b n B
LONGITUDINAL AND LONGITUDINAL PARALLAXES When measuring a stereopair, in addition to the coordinates of points, the differences of these coordinates are used in both images, called parallaxes. different parts left and right shots. For example, in the left image, the point of the object is drawn at point m. In the coordinate system o "Л x Л y Л of this image, it will have coordinates x Л, y L. On the right image, the same point of the object is displayed at point m", and in the coordinate system o "П x П y П it has coordinates x P, y P.
On the coordinates x Л, y Л, plot the position of point m on the right image. The offsets of point m "relative to point m along the x and y coordinate axes are, respectively, longitudinal (letter p) and transverse (letter q) parallaxes. Their values are calculated by the formulas: p = x Л - x П, q = y Л - y P. Longitudinal parallax p is the basis for photographing b at the shooting scale of a given point.This can be seen from the formula, where B is the photographing basis, H is the photographing height, f is the focal length of the camera, m is the denominator of the photographing scale. image area due to changes in photographing height H depending on the terrain. Therefore, by measuring the longitudinal parallaxes on a stereopair, it is possible to calculate the heights on the terrain. Lateral parallax q arises due to the difference in the values of the external orientation elements of the left and right images. BX = X Sп - X Sl does not change the coordinates at P in comparison with the coordinates at L and, therefore, does not cause the appearance of a transverse parallax. BY = Y Sп - Y Sл changing t ordinates in the right image by the value. B Z = Z Sп - Z Sл changes the scale of the right image relative to the left one. The difference between the angles w L and w P, a L and a P, k L and k P cause changes in the coordinates in the images relative to each other.
Obtaining a stereoscopic effect A stereoscopic effect - a three-dimensional vision of the relative position of objects - is obtained due to the fact that each of the two eyes sees the relative position of objects from its own angle of view. left right The brain processes information, creating an overall three-dimensional picture. It is important that in this case the pupils are in constant motion, and this volumetric picture is continuously corrected.
Due to mutual overlap, two adjacent images will show one area of the terrain taken from two different points. If we create such conditions under which each of the images will see only one eye, then the brain will process this information, creating a three-dimensional picture of the relief of the territory. Overlapping area on the working parts of the images The task of image separation (the left eye sees only the left image, and the right eye only the right) is solved by the stereoscope: 1 - large mirror; 2 - lens; 3 - small mirror; 4 - place for the nose 1234 Mirror-lens stereoscope
In addition to the term stereo model, another term is used - stereo effect. Distinguish between direct, reverse and zero stereo effects. The direct stereo effect occurs when the left image is viewed with the left eye, and the right one - with the right (Fig. A, the overlapping parts of the images are covered with a mesh field). If the images are reversed (Fig. B), the physiological parallaxes will change their sign, and the opposite stereo effect will be observed, i.e., for example, hills will be perceived as depressions. If both images are rotated 90 0 and shifted up and down relative to each other (Fig. C), then zero stereo effect will be observed, i.e. two flat images will merge into one flat one. This is due to the fact that the ordinates of points will be established along the eye base, the differences of which are caused by different positions of the images in space, and not by the terrain. Stereo pair measurements are performed with direct stereo effect.
Photo scheme. Photomap Some technological options stereotopographic AFS provides for the preparation of photomaps or orthophotomaps. A photographic map (orthophotomap) is a photographic image of the area, composed of transformed images (orthophotographs) of the same scale. A photographic image of the area, composed of planned images, is called a photographic scheme. Their accuracy is lower than the accuracy of photographic plans, therefore they are used for approximate quantitative estimates in forestry, land management, etc. A photographic map (orthophotomap) is a photographic image of the area, composed of transformed images (orthophotographs) of the same scale. A photographic image of the area, composed of planned images, is called a photographic scheme. Their accuracy is lower than the accuracy of photographic plans, therefore they are used for approximate quantitative estimates in forestry, land management, etc. Photo schemes are single-route and multi-route. Transformation is the process of converting photographs from oblique to horizontal, while simultaneously bringing them to a given scale. The transformation principle consists in the fact that from a photograph it is possible to restore a bunch of projection rays such as was obtained in AFA during shooting, and with the help of these rays, project the image of the photograph onto a horizontal surface. The device with which the transformation technology is realized is called a phototransformer. Depending on the intended purpose, topographic and special photographic plans are distinguished. The first ones are compiled in a national distribution in compliance with the instructions and guidelines for topographic surveys. Special photographic plans are, as a rule, in a random pattern, and they must meet the requirements of departmental instructions.
Photomaps are composed of transformed images by assembling them on the basis of control points. The photographic plan is made on a rigid basis (paper glued to aluminum, aircraft plywood or plastic), on which markers, points of a geodetic network and transformation points are plotted along coordinates in a given scale. This is done either by editing individual photographs or by optical editing with simultaneous transformation by zones. The main processes of drawing up the first of these methods are: preparatory, editing of images, quality control of the photographic plan and its design. Preparatory work includes: selection of photographs along the trapezoid and along the routes within the trapezoid; control of their quality and accuracy of transformation; punching holes with a diameter of about 1 mm at all control points, transformation points, and points of the geodetic network.
Editing begins with the left shot of the northern route. It is laid on the base, the errors of alignment of the centers of the holes with the points on the base are averaged and fixed with weights. Then the second image is placed on the base, the holes are also aligned with the pivot points and, fixing it, the convergence of the contours in the overlap zone is checked. To do this, a clear outline is punctured in the upper picture and check where it ended up in the lower picture. The deviation of the inclination from the contour should not exceed 0.7 mm. After that, both images are cut simultaneously approximately in the middle of the longitudinal overlap. The cut line should not pass through critical paths and along linear objects. Crops from each picture are saved for later control, and the corresponding parts of the first and second pictures are glued to the base. Similar operations are performed when joining the second and subsequent images of a strip, as well as when editing images of adjacent strips. But in the latter case, the control of the convergence of the contours, as well as the cut, is also carried out along the transverse overlaps.
Deciphering the APS Under the decryption is meant the identification, recognition and determination of the characteristics of the terrain objects depicted in the photographs. Interpretation types: - topographic; - special (agricultural, forestry, geological, ecological, military, hydrological, etc.). Topographic - shows information about the elements on the Earth's surface (quantitatively and qualitatively). Special - allows you to carry out regional and topological zoning of the area to study the processes occurring on the Earth's surface for solving special problems. Decryption methods: a) field; b) aerovisual; c) cameral; d) combined; Deciphering signs: direct, indirect, complex.
Direct - those properties of objects that are transmitted directly and are uniquely perceived by the decoder. The direct ones include: shape, size, shadow, phototone, structure, length. Indirect deciphering signs indicate the presence or characteristics of an object that is not depicted in the image or is indeterminate by direct signs, and also eliminate the ambiguity or ambiguity of direct signs. Complex deciphering signs are a combination of direct and indirect signs. Topographic decoding is performed in order to identify, recognize and determine the characteristics of terrain objects, which must be applied to the plan in accordance with the requirements of the current conventional signs. Deciphering images in the process of surveying the area in nature is called field. Recognition of objects and contours in photographic images without examining them in nature is called cameral decoding. Depending on the topographic knowledge of the mapped area and the accepted technology of work, field interpretation is carried out before or after office.
