Space forward rendezvous calculation steps are: 1. by the known external azimuth elements and the coordinates of the image point, the calculation of the image of the spatial auxiliary coordinates; 2. by the external azimuth elements, the calculation of the photographic baseline component Bx, By, Bz; 3 calculation of projection coefficients N1, N2; 4 and finally by the forward rendezvous formula for calculating the ground point of the ground photogrammetric coordinates. Since N1 and N2 have been derived, the YA should be averaged when calculating the ground coordinates is to eliminate the effect of the residuals present in the relative orientation.
23, spatial backward intersection - forward intersection method
Field image control measurement
Stereo coordinate measuring instrument to measure the coordinates of the image point
spatial backward intersection calculation of the image of the external azimuth element
spatial forward intersection calculation of the ground coordinates of the unknown point
24, analytical method of relative orientation
Relative Orientation
This is a method of relative orientation. /p>
Temporarily do not consider the absolute position and attitude of the image, but only to restore the relative position and attitude between the two images, so that the establishment of the stereo model is called the relative stereo model, its scale and orientation are arbitrary; then on this basis, the two images as a whole for scaling, translation and rotation to achieve the absolute position. This method is called relative orientation -- absolute orientation
The process of solving the relative orientation elements by analytical calculation is called analytical relative orientation. Since no absolute position of the image is involved, no control points are required.
The intersection of pairs of rays of the same name is the theoretical basis of relative orientation.
Relative orientation of consecutive image pairs is to find the relative orientation elements of the right image with respect to the left image by taking the left image as the reference
Left image: Xs1=0, Ys1 =0, Zs1 =0 j1= w1 =k1 = 0
Right image: Xs2=bx,, Ys2 =by, Zs2 =bz , j2 , w2 , k2
Relative orientation elements for by, bz, j2 , w2 , k2 5
Individual pairs of relative orientation is the photographic baseline as the image of the X-axis of the spatial auxiliary coordinate system, to the left photographic center S as the origin, the main optical axis of the left image and the photographic baseline B composed of the main kernel plane (the left main kernel plane) for the XZ-plane, constituting right-handed right-angled coordinate system. At this time, the relative orientation elements of the left and right images are:
Left image: Xs1=0, Ys1 =0, Zs1 =0, j1, w1=0, k1
Right image: Xs2=bx=b, Ys2 =by=0, Zs2 =bz=0, j2, w2, k2
Relatively oriented elements of 5 j1, k1, j2, w2, k2
The intersection of pairs of rays of the same name indicates that the rays S1a1, S2a2 , and the photographic baseline B lie in the same plane, i.e., the three-vector S1a1, S2a2 , and B*** planes. According to vector algebra, the three-vector *** plane, their mixed product is equal to zero, that is:
Continuous image of the relative orientation elements of the solution process
① In the stereo-coordinate measuring instrument, measure the image point coordinates of the six selected orientation points (x1, y1) and (x2, y2).
② Determine the initial values: assuming the left image slice is horizontal, the left slice rotation matrix R1 is a unit array; the initial values of the corner elements j,w,k and m,g of the right slice are taken to be zero; and bx is taken to be the left and right parallaxes of the No.1 point in the oriented points (x1, x2).
3) According to the initial value, calculate the right slice rotation matrix R2.
4) According to the input image point plane coordinates, calculate the image space auxiliary coordinates:
5) According to the given initial value, calculate by, bz, and according to the image space auxiliary coordinates, calculate the projection coefficients of each point, N1 , N2.
6) According to the operating equation of relative orientation of the continuous image pair Calculate the constant term and coefficient term of the error equation for each orientation point, and compose the error equation.
(vii) Calculate the coefficient matrix and constant term of the normal equation, and solve the normal equation to find the correction number of the unknown.
⑧ Find the new value of the unknown, i.e., the initial value plus the number of corrections.
9 check whether the number of corrections to the unknown is greater than the limit, if greater than the limit, then repeat the ③ to ⑧ step of the calculation, until all the corrections are less than the limit.
25, the model point coordinates of the calculation
The establishment of photogrammetric coordinate system P-XpYpZp, it is like the auxiliary coordinate system of space and coordinate axes are parallel to each other, the origin of P in the Z1 axis, and the distance from the S1 mf. Here, m for the scale of the image film, f for the main distance of the camera. Then the photogrammetric coordinates of the point S1 are (0, 0, mf).
26, analytic absolute orientation
The purpose of analytic absolute orientation is to transform the photogrammetric coordinates derived after relative orientation to ground measurement coordinates.
Absolute orientation of the solution process
(1) Determine the initial value of the parameters to be determined: Φ0 = Ω0 = К0 = 0, λ0 = 1, ΔX = ΔY = ΔZ = 0.
(2) Calculate the center of gravity of the photogrammetric coordinate system on the ground and the center of gravity of the coordinates.
(3) Calculate the coordinates of the center of gravity of the photogrammetric coordinate system and the gravity-centered coordinates.
(4) Calculate the constant term
(5) Compose the total error equation.
(6) Solve the point-by-point normalization and the normal equation to obtain the correction number of the parameter to be determined.
(7) Calculate the new values of the parameters to be determined
(8) Determine whether dΦ, dΩ, and dК are all less than the given limit ε. If they are greater than the limit ε, repeat the calculation; otherwise, the calculation process ends.
27, dual-image analytical photogrammetry commonly used in the comparison of the three methods
① the first method of pre-intersection of the results depend on the accuracy of the space back rendezvous, pre-intersection process does not take full advantage of the redundant conditions of the leveling calculations;
② the second method of calculating the formula is more, the final accuracy of the point depends on the relative orientation and the absolute orientation of the accuracy of the solution results of the method can not strictly express an image of the The solution result can not strictly express the outer orientation elements of an image;
③ The third method has the most rigorous theory and the highest precision, and the coordinates of the points to be determined are calculated exactly according to the original understanding of the least squares method.
28, the definition, purpose, meaning, classification of analytical aerial triangulation
In the double image analytical photogrammetry, each image pair has to be measured in the field to find four ground control points. This field workload is too large and inefficient. Can only a dozen image pairs in an air strip, or several air strips constitute a regional network, a small number of field control points, in-house analytical photogrammetry method encrypted out of each image pair of control points required, and then used for mapping? The analyzing method of aerial triangulation is the method proposed to solve this problem.
Analytical aerial triangulation refers to the use of photogrammetric analysis to determine the external orientation elements of all images in the region.
The significance of the photogrammetric method of determining (or encrypting) the coordinates of points lies in:
Without directly touching the target or object to be measured, all the targets that can be seen on the image can be determined in terms of their positions and geometries without being restricted by the ground visibility conditions;
The determination of the points can be carried out quickly and simultaneously over a large range of areas, which saves a large amount of field survey
When the photogrammetric leveling is calculated, the accuracy within the encrypted area is uniform and rarely affected by the size of the area;
In terms of the traditional methods, according to the mathematical model used in the leveling, it can be divided into the aerial tape method, the independent model method, and the beam method.
Based on the size of the leveling range, analytical airborne triangulation can be categorized into the single-model method, the single air strip method, and the area network method.
The air strip method is to establish a free air strip first by relative orientation and model connection, to take the photogrammetric coordinates of the point in the strip as the observation value, and through the determination of the transformation parameter in the nonlinear polynomials, to make the free net to incorporate the required ground coordinate system, and to minimize the sum of the squares of the discrepancy values on the public **** points.
The independent model method of leveling is to first establish a unit model by relative orientation, take the coordinates of the model points as the observation values, and through the similar transformation of the unit model in the space, make it incorporate into the required ground coordinate system and make the sum of squares of the residuals on the model connecting points to be the minimum.
The beam rule starts directly from the beams of light of each image, takes the coordinates of the image points as the observables, and encrypts the object coordinates of the point to be sought and the orientation elements of the image by means of translations and rotations of each beam in three-dimensional space so that the rays of light of the same name meet optimally in the object side and are made to be incorporated into a prescribed coordinate system.
29, GPS-assisted airborne triangulation principle
GPS-assisted airborne triangulation refers to the use of airborne GPS receiver and the ground reference point of the GPS receiver at the same time, fast, continuous recording of the same GPS satellite signals, through the relative positioning technology, offline data post-processing to obtain the camera exposure time of the station's high-precision three-dimensional coordinates, which will be used as a regional Network leveling in the additional non-photogrammetric observations, to replace (or reduce) ground control with aerial control; through the use of unified mathematical models and algorithms, the overall determination of the point position and the quality of its assessment of the theory, technology and methods.
Chapter 4
30, digital photogrammetry definition
Using digital gray scale signals, using digital correlation technology to measure the same name like points, on the basis of analytical calculations, relative orientation and absolute orientation, the establishment of digital three-dimensional model, so as to establish a digital elevation model, drawing contour lines, the production of orthophotos, as well as for the geographic information system to provide the basis of information, etc., but also for the full digital photogrammetry. information, etc., also for fully digital photogrammetry.
31, image digitization and image resampling
Transparent positive (or negative) on the image digitizer, the image of the gray scale value of the image points on the film recorded in digital form, known as image digitization.
The gray scale of an image, also known as the optical density, reflects the degree of transparency, i.e., the ability to transmit light, the transmittance T. The gray scale of an image is expressed as the logarithm of the opacity.
The measurement process of discretizing the actual continuous function model is sampling, and the points being measured are called sample points, with the distance between the sample points being the sampling interval. The gray values of the points are taken as integers, a process known as quantization of the image gray scale.
32, digital image orientation
In the digitization process of film scanning, the film's scanning coordinate system and the image plane coordinate system is generally not parallel, and the origin of the coordinates are different, so the same image point like the plane coordinates x, y and its scanning coordinates x', y' is not equal, need to be converted to this conversion is known as the digital image of the internal orientation.
33, based on gray-scale image correlation
From the left and right digital image to find the same image point, that is, the digital image correlation, is the core of the all-digital photogrammetry. Firstly, we take out the image signal in the small area centered on the point to be determined, and then we take out the image signal in the corresponding area in another image, calculate the correlation function between the two, and take the center point of the corresponding area corresponding to the maximum value of the correlation function as the homonymous point.
Methods: correlation coefficient method, covariance method, high-precision least squares correlation.
34, nuclear line and nuclear surface, nuclear line correlation
Through the photographic baseline S1S2 and any object square point A made by the plane WA is called through the point A of the nuclear surface. The nuclear plane through the main point of the image is called the main nuclear plane. In the stereo image pair, the left and right images have their own main nuclear surface, generally the two main nuclear surface is not overlap. The line of intersection between the nuclear plane and the image plane is called the nuclear line. In a nuclear line on any point in another image of its homonymous image point must be located in its homonymous nuclear line.
Kernel line correlation
35, the concept of feature-based image matching, commonly used methods
Concept: image matching is mainly used to align those feature points, lines or surfaces. Feature matching can be divided into three steps: ① feature extraction; ② use a set of parameters to describe the features; ③ use the parameters for feature matching.
Point feature extraction algorithm: Moravec operator, Forstner operator
Line feature extraction operator: commonly used methods are differential operator, Laplace operator, LOG operator, etc.
Comparison of edge detection operator
36, cross-connection method of image matching
l. Feature extraction: the use of feature segmentation method, respectively. The point features or line features are extracted along the kernel line for the left and right images, and the features on a kernel line are defined as a feature segment composed of three feature points (zero intersection point Z and two inflection points S1,S2).
2. Composition of spanning method matching window: the so-called spanning method window structure is to connect two or even more neighboring features to form a window.
3. Cross-joining image matching
(1) On the left image, Fb and Fe are the aligned and to-be-matched features respectively to form the target window
(2) On the right image, Fb is the aligned feature, and a number of features are selected on the right image
(3) Compare the feature parameters of the to-be-matched feature Fe with the alternative features, and select similar features to be matched
(4) Compare the feature parameters of the to-be-matched features and alternative features, and select similar features. features
(4) On the right image, a different matching window is constituted by using Fb as one end feature of the window and the selected alternative features as the features at the other end of the window
(5) The matching window is resampled so that its size is always equal to the length of the target window of the left image, thus eliminating the effect of the geometric distortion on the correlation.
(6) The correlation coefficients between the target window and the resampled matching window are calculated, and the homonymous features of Fe are determined by the criterion of maximum correlation coefficient.
4. Edge tracking, transfer of matching features
37, the development of digital photogrammetric system history, composition, function
In the 1960s, the first analytical mapper AP-1 was introduced shortly after the United States has also developed a fully digital mapping system DAMC.
In 1988, Kyoto, the 16th General Assembly of the International Society for Photogrammetry and Remote Sensing (ISPRS)
In 1988, the 16th Congress of the International Society for Photogrammetry and Remote Sensing (ISPRS) in Kyoto, commercial digital photogrammetric workstation DSP-1 was displayed.
July 1996, in Vienna, 17th International Conference on Photogrammetry and Remote Sensing, a dozen sets of digital photogrammetric workstations on display, which indicates that the digital photogrammetric workstations have entered the stage of use.
Hardware Composition: Computer;
External Equipment: Stereoscopic Observation Equipment; Operation Control Equipment
Input Equipment: Image Digitizer
Output Equipment: Vector Plotter; Raster Plotter
Software Composition:
Digital Image Processing Software Mainly Includes: Image Rotation; Image Filtering; Image Enhancement; Feature extraction.
Pattern recognition software mainly includes: feature recognition and localization, identification and localization of frame markers; image matching (identification of homonymous points, lines and surfaces); target recognition.
Analytical photogrammetry software mainly includes: orientation parameter calculation; aerial triangulation solution; kernel-line relationship solution, coordinate calculation and transformation; numerical interpolation, digital differential correction; projection transformation.
Auxiliary function software mainly includes: data input and output; data format conversion; notation; quality report; map outline finishing; human-machine interaction.
Functions: image digitization, image processing, measurement (single image, double image, multi-image), image orientation (internal orientation, relative orientation, absolute orientation), kernel image, image matching, automatic aerial triangulation, establishment of a digital elevation model, automatic drawing of contour lines, production of orthophotos, orthophoto mosaics and repairs, digital mapping, production of image maps, the production of perspective maps, landscape maps, Produce stereo matching film.
Chapter 5
38, DTM and DEM concepts, application areas
Digital ground model (DTM) is a data array used to represent the spatial distribution of ground features, the most commonly used is the use of a series of ground points in the plane of the coordinates of the X, Y, as well as the elevation of the ground points of the Z, or the attributes of the data array.
If the ground is regularly arranged in a certain grid form, the plane coordinates X and Y of the points can be deduced from the starting point without the need to record them, so that the ground surface pattern is expressed only in terms of the elevation Z of the points, which is called a digital elevation model (DEM).
The DTM is a finite sequence of n-dimensional vectors defined on an area D. If only the topographic component of the DTM is considered, we usually call it the digital elevation model DEM.
39. The representation of the DEM
The digital elevation model DEM is a finite sequence of 3D vectors that represents the topography of an area D. The DEM is a finite sequence of three-dimensional vectors: ｛Vi= (Xi, Yi, Xi), i=1, 2, .... , 2,...n}, where (Xi, Yi) ∈ D are the plane coordinates and Zi is the elevation corresponding to (Xi, Yi).
(1)Regular Rectangular Grid:Using a series of terrain points in the X, Y direction are equally spaced in the elevation of Z to represent the terrain, forming a rectangular grid DEM
(2)Irregular Triangular Grid TIN:If the points collected according to the terrain features according to a certain rule to connect into a number of triangles covering the entire area and do not overlap each other, constituting an irregular triangular grid TIN
(3)Grid-TIN hybrid network: Professor Ebner of Germany and others proposed a hybrid form of Grid-TIN DEM, the general area using a rectangular network data structure, along the topographic features of the additional triangular network data structure.
40, DEM data point collection method
In order to establish the DEM, it is necessary to measure the three-dimensional coordinates of a number of points, the three-dimensional coordinates of these points are measured called data points.
(1) Ground measurement: The automatic recording of the distance measuring instrument is measured in the field.
(2) Digitization of Existing Maps: A method of digitizing information on existing maps, using a digitizer.
Hand-held tracking digitizer, scanning digitizer, semi-automatic tracking digitizer.
(3) Spatial sensors: data collection using GPS, radar and laser altimeter.
41, the concept, method and characteristics of DEM interpolation
DEM interpolation is based on the elevation on the reference point to find out the elevation on the other points to be determined, which belongs to the interpolation problem in mathematics.
The main methods are moving surface fitting method, weighted average method and least squares configuration method.
(1) The undulating pattern of the entire earth's surface cannot be fitted by a simple low degree polynomial. And the solution of a high degree polynomial is unstable and produces unrealistic oscillations.
(2) The surface of the terrain has the property of being continuous and smooth, but it may also have discontinuities due to natural forces or man-made causes.
(3) Due to the limitations of computer memory, it is not possible to interpolate a mathematical ground model over a large area at the same time.
(4) Therefore, generally always divide the survey area or map into smaller computing units, using local function interpolation method, and interpolation of general data points and terrain features points, lines, and according to the different methods of data point acquisition to take the corresponding interpolation method.
42, moving surface fitting method
It is a point-by-point interpolation method centered on the point to be sought, which defines a new local function to fit the surrounding data points, and then find the elevation of the point to be determined. Usually the coordinate origin is moved to the point to be determined, and the data points used should fall within a circle of radius R.
(l) establish local coordinates: for each grid point of the DEM, retrieve the data points corresponding to the DEM grid point in several chunks of the grid from the data points, and move the coordinate origin to the DEM grid point P (Xp, Yp):
(2) select neighboring data points: in order to select the neighboring data points, take the to-be-determined point P as the center of the circle, and make a circle with a radius of R, with the to-be-determined point P as the center. Any data point falling within the circle is selected.
(3) List the error equation.
(4) Calculate the weight of each data point
(5) Normalize the solution
43. Multi-surface DEM Interpolation
Creates a surface (rotating surface) at each data point, and then superimposes the surfaces in a certain proportion to optimally describe the surface of the object, and then passes strictly through the surface at each data point.
44, DEM data compression methods
Integer storage: the elevation data will be subtracted from a constant Z0, which can be the average elevation of a certain area range, or the first point of the elevation of the region. Expand 10 times or 100 times according to the precision requirement, and keep the integer part after rounding off the decimal part.
Differential mapping: the increment between adjacent data, data range is small, you can use a byte storage of a data, so that the data compression to the original storage volume of nearly a quarter.
Compression coding: when a certain code is designed according to the probability of occurrence of each number, the code with the shortest number of bits (bit) indicates the number with the highest probability of occurrence, and the code with the smaller probability of occurrence is indicated by the code with the longer number of bits, then the average number of bits accounted for by each data is smaller than the original fixed number of bits (16 or 8).
45, triangulation network digital ground model storage method
Triangulation network digital ground model TIN data storage method is very different from the rectangular grid DTM storage method, which not only store the elevation of each dot, but also to store its plane coordinates, the topological relationship of the connection of the network, triangles and neighboring triangles and other information. The commonly used TIN storage structure has the following three forms: direct representation of the dot neighboring relationships; direct representation of the triangle and neighboring relationships; mixed representation of the dot and triangle neighboring relationships.
46, the application of digital ground model
(1) in surveying and mapping can be used to draw contour lines, slope, slope map, three-dimensional perspective map, the production of orthophoto, three-dimensional landscape map, three-dimensional matching piece, three-dimensional terrain model and the map of the repair test.
(2) It can be used for the calculation of volume and area in various projects, the drawing of various sections and the design of lines.
(3) Military can be used for navigation (including missile and aircraft navigation), communications, combat mission planning.
(4) In remote sensing, it can be used as auxiliary data for classification.
(5) In environment and planning, it can be used to analyze the current situation of land use, various planning and flood risk forecasting.
(6) Digital ground modeling is used in surveying and mapping.
47, based on the regular rectangular grid contour drawing method
Automatic drawing of contour lines based on the regular grid DEM consists of the following two main steps:
(1) Use the elevation of the rectangular grid points of the DEM to interpolate the contour points on the edge of the grid, and arrange these contour points in order (i.e., contour line tracking).
1) Determination of contour elevations
2) Calculation of the state matrix
3) Processing of the start and end points of the contour lines
4) Interpolation of contour points
5) Searching for the next contour point
6) Searching for the end point of the contour lines
(2) Using the planar coordinates of these sequential contour points X , Y are interpolated, i.e., the contour points are further encrypted and plotted as smooth curves (i.e., the contour lines are smoothed).
In order to obtain a smooth contour line, interpolation (encryption) is also necessary between these discrete contour points.
There are the following requirements for the interpolation method:
The curve should pass through known contour points (often called nodes);
The curve is smooth at the nodes, i.e., its first-order derivative (or second-order derivative) is continuous;
There is no excess wobble in the curve between two neighboring nodes;
The same contour lines cannot intersect each other themselves.
48, the main process of perspective drawing from the DEM
1, select the appropriate reference surface elevation Z, as well as the magnification of elevation Z m. This is necessary to exaggerate the three-dimensional form of the terrain.
2. Select the appropriate viewpoints XS,YS,ZS; the line of sight t (direction of the line of sight), j (the angle of the line of sight).
3, according to the selected or calculated parameters XS,YS,ZS, a1,a2...c2,c3 and the main distance f to calculate the object side to the image side of the perspective transformation, through the *** line equation of the DEM nodes of the "image point" coordinates x, y.
4, hidden line processing. The process of the hidden lines of the DEM.
5, from the viewpoint of the nearest DTM section, section by section to draw, for the first section of each grid grid, only with a grid grid in front of it connected; for the subsequent sections of each grid grid, not only with the same section of the previous grid grid connected to the former section should be connected with the neighboring grid grid connected to the previous section (of course, the part that is hidden is not drawn).
6, adjust the value of each parameter, you can draw from different directions, different distances from the different forms of perspective drawing animation. When the computer speed is sufficiently high, it can produce animated DTM perspective drawings in real time.