CN1845088A - Computer-generated method of normalized distribution image of direct sunlight on undulating ground - Google Patents

Abstract

The invention relates to a method for generating the graph of sunlight normalized distribution on concave-convex ground, by computer. It comprises: based on GIS, it uses the sun altitude angle/azimuth angle, the digital map (digital ground mode) and the geography coordinate (latitude and longitude) at each point, to use computer point-to-point calculate the sunlight ground irradiate factor at each point of digital map; at last, transforms the sunlight ground irradiate factor at each point into the sunlight distribution map. The inventive sun light distribution map can express the sunlight relative luminance at each point of natural ground that affected by the landform; it can be used in the landform effect correct of sunlight of remote sensing graph, the prediction of radar detecting effect, digital simulation, etc.

Description

Computer-generated method of normalized distribution image of direct sunlight on undulating ground

technical field

The invention relates to a remote sensing and geographic information system technology, in particular, it relates to using a digital topographic map to generate a computer-generated normalized distribution image of direct sunlight on undulating ground.

Background technique

Due to the shading and shielding of the direct sunlight by the terrain, the distribution of direct solar irradiance on the natural surface will change due to the terrain compared with the broad horizontal ground. Obviously, it also changes the comparability of remote sensing data of ground objects in horizontal ground imaging. Affects the quality of remote sensing digital images and the level of quantitative research and application. The influence of terrain on satellite remote sensing digital images and the elimination of mountain shadows and cloud shadows have always been difficult problems in the processing and application of satellite remote sensing digital images. The existing satellite remote sensing digital image processing and application technologies, such as orthophoto image processing technologies, have not fundamentally solved this important technical problem.

Contents of the invention

The object of the present invention is to provide a method for computer generating a normalized distribution image of direct sunlight on undulating ground.

Technical scheme of the present invention is as follows:

According to a computer-generated method of sunlight normalized distribution image on undulating ground according to the present invention, its steps include:

With the support of GIS (Geographic Information System), the digital ground model corresponding to the satellite image is generated by using the solar position parameters (solar altitude angle, solar azimuth angle) and the digital topographic map given by the satellite image, as well as the longitude and latitude of each point. Coordinates, the computer calculates the direct solar light topographical irradiation coefficient of each point on the digital topographic map point by point, and finally converts the obtained direct solar light topographical irradiation coefficient of each point into a direct solar light distribution map.

The sun elevation angle and azimuth angle of each point on the described satellite remote sensing digital image are:

θ _ij = arcsin(sinφ*sinδ+cosφ*cosδ*costij),

Aij＝arcsin(sinθ _ij *sinφ-sinδ)/cosθ _ij *cosφ),

δ=arcsin(sinθ*sinφ-cosθ*cosφ*cosA),

t=arcsin(cosθ _ij *sinA/cosδ)+Δλ,

Among them: θ, A, δ: the altitude angle, azimuth angle, and solar declination angle of the sub-satellite point in the satellite images; λ, φ: the geographic longitude and latitude of the sub-satellite point, respectively. Δλ is the longitude increment from the pixel point to the sub-satellite point;

The judgment of the mountain body and cloud layer shadow on the satellite remote sensing digital topographic map is to utilize the digital topographic map registered with the satellite remote sensing digital image and the position parameters (elevation angle, azimuth angle) of the sun of the satellite picture element to carry out the mountain body and cloud layer shadow detection. shadow judgment. The judgment criterion is: the maximum terrain (cloud layer) altitude angle of the pixel point in the direction of the sun is equal to or greater than the sun altitude angle of the pixel point, that is: DH(i, j) _≥θij , then the pixel point is a shadow; otherwise, it is not a shadow;

The topographical illumination coefficient of direct solar light at the shadow midpoint on the digital topographic map: Fij=0.

The non-shaded point (the sun) direct light terrain illumination coefficient on the digital topographic map:

F _ij ＝1-tgα _ij ctgθ _ij cosω _ij ω _ij ＝AL _ij -A _ij

Among them: the solar height θ _ij and azimuth AL _ij of the pixel surface are given by the annotation of the satellite image, and the surface slope of the pixel α _ij , aspect A _ij and longitude and latitude of the pixel are given by the corresponding digital ground model of the satellite image.

The computer-generated and visualized view of the distribution map will be arranged according to the original row and column order of the obtained topographic illumination coefficients of direct sunlight at each point and linearly stretched and calculated point by point:

GNij=INT(Fij×MAX(DN)/F)+0.5); I=1, 2, 3...M; J=1, 2, 3...N

F=INT(MAX((Fij); I=1, 2, 3...M; J=1, 2, 3...N)

DN: image brightness value; MAX(DN)=2K=-1 is the maximum brightness value. M and N are the maximum vertical and horizontal pixel numbers of the image respectively.

Compared with the prior art, the present invention has advantages and positive effects:

The direct solar light distribution diagram generated by the method of the present invention expresses the relative illuminance of direct solar light at each point on the natural ground under the influence of topography and the degree of visibility to the sky. The computer-generated direct solar light distribution (normalized) image quantitatively, intuitively and visually reflects the relative distribution of direct solar irradiance on the natural surface. It plays an important role in the correction of the terrain influence of direct sunlight on remote sensing images, the prediction and digital simulation of radar detection effects, the computer production of blurred maps, the automatic discrimination of terrain shadows on satellite images, and the research on the redistribution of natural light radiation on the ground. .

Description of drawings

Figure 1 is a 1:100,000 digital topographic map (stereoscopic, 1024×1024) of the Longyan area in Fujian, China, as measured by satellite telemetry;

Fig. 2 is a computer-generated program flowchart of an embodiment of the present invention;

Fig. 3 shows the linear stretching of the direct solar light topographic distribution conversion coefficients for the digital topographic map of Fig. 1 according to the method of the present invention. Express the real normalized distribution image of the direct solar radiation on the undulating ground at the moment of imaging (the illuminance of the direct solar radiation on the horizontal ground is 1).

Detailed ways

A preferred embodiment of the present invention is given below with reference to FIGS. 1 to 3 , and is described in detail so as to better illustrate the features and functional characteristics of the present invention, rather than to limit the scope of the present invention.

Please refer to FIG. 1 , which shows the satellite telemetry digital topographic map of the Longyan area in Fujian Province, China to be studied in this embodiment.

Please refer to Fig. 2, step 1000, start the computer generation program 100 of the present embodiment residing in the GIS geographic information system, step 1001, input the digital topographic map of the area to be studied in the present embodiment as shown in Figure 1, and carry out Registration adjustment, determining the grid, step 1002, selecting the first point (grid) on the digital topographic map. Step 1003 calculates the sun elevation angle, the azimuth angle of each point on the digital topographic map:

θ _ij ＝arcsin(sinφ*sinδ+cosφ*cosδ*costij)

Aij＝arcsin( _sinθij *sinφ-sinδ)/ _cosθij *cosφ)

δ=arcsin(sinθ*sinφ-cosθ*cosφ*cosA)t=arcsin( _cosθij *sinA/cosδ)+Δλ

θ, A, δ: the sub-satellite point solar altitude angle, azimuth angle and solar declination angle in the satellite image notes; λ, φ: the geographic longitude and latitude of the sub-satellite point, respectively. Δλ is the longitude increment from the pixel point to the sub-satellite point. Step 1004, judging the shadows of mountains and clouds on the digital topographic map:

Using the digital topographic map registered with the satellite remote sensing digital image and the sun's position parameters (elevation angle, azimuth angle) of the pixel of the satellite image are used to judge the shadow of the mountain body and the cloud layer. The judgment criterion is: the maximum terrain (cloud layer) altitude angle of the pixel point in the direction of the sun is equal to or greater than the sun altitude angle of the pixel point, that is: DH(i, j) _≥θij , then the pixel point is a shadow; otherwise, it is not a shadow. Step 1005 calculates each point ground (slope surface) direct sunlight topographical illumination coefficient on the digital topographic map:

For the shaded and non-shaded points on the digital topographic map, calculate the terrain illumination coefficient of direct sunlight

(A) Calculation of the topographical illumination coefficient of direct sunlight on the point in the shadow on the digital topographic map:

Because the direct solar illuminance of the point in the shadow on the digital topographic map is 0, so its direct solar light terrain illumination coefficient: Fij=0;

(B) Calculation of the direct solar light topographical illumination coefficient of non-shaded points on the digital topographic map:

The terrain illumination coefficient calculation of direct solar light at non-shaded points on the digital topographic map is as follows:

F _ij ＝1-tgα _ij ctgθ _ij cosω _ij ω _ij ＝AL _ij -A _ij pixel surface sun elevation angle θ _ij , azimuth angle AL _ij is given by satellite image notation, pixel ground slope α _ij , slope The direction A _ij and the longitude and latitude of the pixel are given by the corresponding DTM (digital terrain model generated by the digital topographic map) of the satellite image. Step 1006 judges whether all points (grids) have been calculated? If the calculation is not completed, execute step 1007, jump back to step 1003, otherwise execute step 1008; step 1008, step 1009 computer generation and visualization of the sun direct light (normalized) distribution image on the undulating ground: the sun at each point will be obtained The terrain illumination coefficients of direct sunlight are arranged in the original row and column order and linearly stretched and calculated point by point to realize the mapping and visualization of the normalized coefficients of terrain illumination of direct sunlight:

GNij=INT(Fij×MAX(DN)/F)+0.5); I=1, 2, 3...M; J=1, 2, 3...N

F=INT(MAX((Fij); I=1, 2, 3...M; J=1, 2, 3...N)

DN: image brightness value; MAX(DN)=2K=-1 is the maximum brightness value. M and N are the maximum vertical and horizontal pixel numbers of the image respectively. Finally, step 1010 is executed and the program ends.

Claims (6)

1. A computer-generated method of direct sunlight normalized distribution image on undulating ground, its steps comprising: With the support of GIS, using the sun position parameters, the digital topographic map and the geographic coordinates of each point, the computer calculates the direct solar light topography irradiation parameters of each point on the digital topographic map point by point, and finally obtains the direct solar light topography of each point The irradiance factor is transformed into a direct solar light distribution map. Said sun position parameter refers to the sun elevation angle and azimuth angle where the corresponding point is located on the digital topographic map; said geographical coordinates of each point refer to the corresponding longitude and latitude. 2. the computer generation method of direct sunlight normalized distribution map on the undulating ground according to claim 1, is characterized in that: Calculation of the sun altitude angle and azimuth angle of each point on the satellite remote sensing digital image: θ _ij ＝arcsin(sin*sinδ+cos*cosδ*cost _ij ) A _ij ＝arcsin( _sinθij *sin-sinδ)/ _cosθij *cos) δ=arcsin(sinθ*sin-cosθ*cos*cosA)t=arcsin( _cosθij *sinA/cosδ)+Δλ Among them, θ, A, δ: the altitude angle, azimuth angle and solar declination angle of the sub-satellite point in the satellite image notes; λ, : the geographic longitude and latitude of the sub-satellite point, respectively. Δλ is the longitude increment from the pixel point to the sub-satellite point. 3. The computer-generated method of the normalized distribution image of direct sunlight on the undulating ground according to claim 1, characterized in that: the judgment of mountain body and cloud layer shadow on the satellite remote sensing digital topographic map. Using the digital topographic map registered with the satellite remote sensing digital image and the sun's position parameters (elevation angle, azimuth angle) of the pixel of the satellite image are used to judge the shadow of the mountain body and the cloud layer. The judgment criterion is: the maximum terrain (cloud layer) altitude angle of the pixel point in the direction of the sun is equal to or greater than the sun altitude angle of the pixel point, that is: DH(i, j) _≥θij , then the pixel point is a shadow; otherwise, it is not a shadow. 4. according to the computer generation method of the direct sunlight normalized distribution map on the undulating ground of claim 1, it is characterized in that, the direct sunlight topographical illumination coefficient of the shadow midpoint on the digital topographic map: F _ij =0. 5. the computer generation method of direct solar light normalized distribution map on undulating ground according to claim 1, is characterized in that, Terrain illumination coefficient of direct light on non-shaded points (the sun) on the digital topographic map: F _ij ＝1-tgα _ij ctgθ _ij cosω _ij ω _ij ＝AL _ij -A _ij Among them: the solar height θ _ij and azimuth AL _ij of the pixel surface are given by the annotation of the satellite image, and the surface slope of the pixel α _ij , aspect A _ij and longitude and latitude of the pixel are given by the corresponding digital ground model of the satellite image. 6. the computer generation method of direct solar light normalized distribution map on the undulating ground according to claim 1, it is characterized in that, the computer generation of distribution map is visualized according to the direct solar light topographical illumination coefficient of each point obtained by The original rows and columns are arranged in order and linear stretch calculation is performed point by point; GN _ij =INT(F _ij ×MAX(DN)/F)+0.5); I=1, 2, 3...M; J=1, 2, 3...N F=INT(MAX((F _ij ); I=1, 2, 3...M; J=1, 2, 3...N) DN: Image brightness value; MAX(DN)=2 ^K ＝-1 is the maximum brightness value. M and N are the maximum vertical and horizontal pixel numbers of the image respectively.

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