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A Method of Extracting Star Image from Star Chart

A star map and star image technology, which is applied in the field of star image extraction from the star map, can solve the problems of complex calculation process and low star image extraction rate, achieve high precision, avoid repeated judgment of star image pixels, and fast speed Effect

Inactive Publication Date: 2016-06-08
CHANGZHOU INST OF TECH +1
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  • Summary
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  • Claims
  • Application Information

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Problems solved by technology

In 2006, Li Chunyan et al. proposed a star image centroid algorithm based on the sub-pixel correlation method in "Optoelectronic Engineering" Vol. Correlation function, calculate the position of the star image by calculating the maximum value of the correlation function, the calculation accuracy is better than 1 / 12 pixel, due to the complicated calculation process, the star image extraction rate is low

Method used

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  • A Method of Extracting Star Image from Star Chart
  • A Method of Extracting Star Image from Star Chart
  • A Method of Extracting Star Image from Star Chart

Examples

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Embodiment 1

[0031] A method for extracting star images from star charts, comprising:

[0032] Step 1, set the gray value of the pixel in the background area of ​​a star map to 0, and the gray value of the pixel in the star image to be non-zero; traverse the star map to convert the star map into a cross-linked list; extract The coordinates (x, y) and gray value f(x, y) of the star image pixel whose gray value is not 0, and the coordinates (x, y) and gray value f(x, y) of the star image pixel ( x, y) are stored in the nodes of the cross-linked list;

[0033] Furthermore, in order to better achieve the purpose of separating the star image and the background, the threshold value of the fixed threshold method is approximately equal to the mean value of the background gray level, and the centroid algorithm with a threshold has high precision.

[0034] The fixed threshold method first processes the star map with the gray threshold T, which is calculated by the following formula,

[0035]

...

Embodiment 2

[0053] On the basis of embodiment 1, the method for extracting star images from the star map of the present invention, its specific steps include:

[0054] Step 1, define M as a cross-linked list. Traversing the star map to convert the star map into a cross-linked list M; where the pixel positions and gray values ​​whose grayscale is greater than the threshold are extracted and stored in the nodes of the cross-linked list M.

[0055] Step 2, define three variables ACC1, ACC2, ACC3 as accumulators, and initialize them to 0. Take the first node of the cross list as the initial seed.

[0056] Step 3, extract the coordinates (x, y) and gray value f(x, y) of the current seed, and add xf(x, y), yf(x, y), f(x ,y). According to the row vector pointer right and column vector pointer down of the current seed, extract the right and bottom nearest neighbor pixels, which are recorded as rightnode and downnode. Calculate the nearest neighbor pixels on the left and top from the row numbe...

Embodiment 3

[0063] On the basis of Example 1 and Example 2, the present invention is further verified by further extraction efficiency.

[0064] The star map is processed on a DELL computer (model is DIMENSION4600, CPU is Pentium4, 2.80GHz, memory capacity is 512M). 1000 simulated star maps with a resolution of 1024×1024 pixels were randomly generated, and a total of 20347 star images were extracted from these 1000 star maps, with an average of 20 star images per star map.

[0065] The time for the inventive method to process each star map is as follows: figure 2 As shown, the extraction time of 55.5% of star maps and star images is 16 milliseconds, and the extraction time of 44.5% of star maps and star images is 15 milliseconds. Generally speaking, the time for the method of the present invention to process a star map is about 16 milliseconds, which is proportional to the total number of star image elements and has nothing to do with the number of stars in the star map. These times are...

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Abstract

The invention relates to a method for extracting star images from a star chart. The method comprises steps of (1) converting the star chart to an orthogonal list and storing coordinates (x, y) and grey-scale values f (x, y) of a pixel of a star image to a node of the orthogonal list; (2) defining three variables of which original values are zero as three accumulators, wherein the three variables are ACC1, ACC2 and ACC3 respectively; (3) communicating a star image region through a region increasing algorithm, adding xf (x, y), yf (x, y) and f (x, y) for the three accumulators respectively, and deleting the node of which the coordinates (x, y) and grey-scale values f (x, y) are extracted; repeating the step (3) until the star image region is communicated; (4), calculating barycentric coordinates (xc, yc) and luminance Y of the star image by using the three accumulators; and (5), setting the three accumulators to be zero, and repeating the step (3) and the step (4) until the orthogonal list is hollow, i.e., all star images are extracted completely.

Description

technical field [0001] The invention belongs to the technical field of celestial navigation and relates to a method for extracting star images from a star map. Background technique [0002] Accurate attitude information provides an important guarantee for the smooth flight of the spacecraft. The star sensor is currently the most accurate attitude measurement instrument. The working process is mainly composed of star map acquisition, star image extraction, star map recognition, attitude estimation and other steps. Star image extraction is the process of obtaining data such as star image brightness and position by processing star images, which is the prerequisite for smooth star image recognition. With the increase of the image sensor array used, the processing time of star image extraction increases, and the problem of timeliness becomes prominent. The study of fast star image extraction algorithm is of great significance for improving the attitude measurement rate and devel...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06T7/00G06T1/00
Inventor 朱锡芳吴峰沈为民许清泉
Owner CHANGZHOU INST OF TECH
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