JP2507973B2 - Automatic cloud amount evaluation device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic cloud amount evaluation device, and more particularly to an image catalog creation device for judging whether observation results are effective or ineffective for image processing in the observation data of an earth observation satellite equipped with an optical sensor based on cloud amount. The cloud amount evaluation method of.

[0002]

2. Description of the Related Art In an earth observation satellite equipped with an optical sensor, it is usually possible to observe a plurality of spectrum bands. It is known that in the spectrum band where visible light can be observed, the level of observation data in the part corresponding to clouds becomes higher than the level of land and sea.

On the other hand, if there are many clouds in the observation data, it is impossible to obtain the land and sea data that originally require the use of image data, so it is judged in advance from the image catalog whether or not the image is a process-effective image. Often.

In this image catalog, for example, the observation time of the earth observation satellite is 15 minutes, and one observation unit (one scene) is one.
If it is 0 seconds, 90 scenes will exist, and the amount of data in the image catalog will be enormous depending on the observation period. Therefore, it is required that the cloud amount value required for the image catalog be entered into the image catalog reliably and automatically.

Conventionally, in the cloud amount evaluation method of an image catalog creating apparatus, when the cloud amount is evaluated for one observation unit (one scene), a simple threshold comparison is performed on all input data. In this threshold comparison, all input data that exceeds the threshold is determined to be a cloud, and the ratio of the total number of data in one observation unit (one scene) to the number of data determined to be a cloud is calculated. The cloud amount value for one scene) is calculated.

[0006]

In the conventional cloud amount evaluation method described above, the cloud amount is calculated irrespective of the type of cloud, and, for example, a "streak cloud" spreads over one observation unit (one scene). In such a case, the cloud amount value is small, but the cloud amount may be judged to be small even for images in which land and sea data cannot be obtained in a aggregated form so that it can be effectively used.

In this case, the operator has to manually perform the cloud amount value changing process of the image catalog while looking at the image again, and there is a problem that the influence on the operation cannot be ignored, such as an increase in operation time.

Therefore, an object of the present invention is to solve the above problems, to provide an automatic cloud amount evaluation device capable of reducing the work of reviewing and correcting the cloud amount evaluation result of an image catalog and reducing the operational load. To do.

[0009]

An automatic cloud amount evaluation apparatus according to the present invention is an automatic cloud amount evaluation for evaluating cloud amount in a plurality of scan data obtained by a scanning operation of an optical sensor of an earth observation satellite and each consisting of a plurality of pixel data. In the apparatus, a discriminating means for discriminating whether or not the pixel data is a cloud by comparing the pixel data with a preset threshold value, and n obtained by dividing the scan data into n equal parts (n is a positive integer). Counting means for counting the number of data discriminated as the cloud by the discriminating means for each division unit, and determination for determining whether or not each division unit of the scan data is a cloud based on the counting result of the counting means And means for calculating the cloud amount within a preset observation range from the determination result of the determination means obtained for each division unit of the scan data.

[0010]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the figure, the comparison circuit 1 compares all the input data with a threshold value, and when the data exceeds the threshold value, it is determined to be a cloud. When the comparison circuit 1 determines that the data is a cloud, it outputs that fact to the counter 2.

The counter 2 is provided with n counters for counting the determination result of the comparison circuit 1 for each scan data from the optical sensor (not shown) of the earth observation satellite divided into n equal parts (n is a positive integer). Has been done.

Each of the n counters 2 (1) to 2 (n) has been cleared before the start of counting, and the latch / clear control circuit 3 outputs the data determined by the comparison circuit 1 to be a cloud in each area. It is controlled to count up when input.

The latch / clear control circuit 3 controls the counters 2 (1) to 2 (n) to take charge of respective scan data divided into n equal parts in advance according to the scan start timing from the earth observation satellite.

For example, if data of 1 pixel is obtained by one scan by the optical sensor, this 1 1 pixel is obtained.
It is considered that the pixel data forms one area with m lines (m scans).

The latch / clear control circuit 3 controls the counters 2 (1) to 2 (n) to take charge of each of n small sections (division units) obtained by equally dividing this area into n. That is, each of the counters 2 (1) to 2 (n) has (l1 / n) *
It will be in charge of m pixel data.

Each of the counters 2 (1) to 2 (n) outputs the counting result to the arithmetic circuit 4 when the counting of the data determined to be a cloud is completed in each of the small sections in charge thereof. The arithmetic circuit 4 calculates the cloud amount value of the corresponding small section based on the counting results of each of the counters 2 (1) to 2 (n). The calculation formula is the number of pixels exceeding the threshold value / the total number of pixels in the small section. Here, the total number of pixels in the small section =
(L1 / n) * m.

For example, when the result that the cloud amount value exceeds 40% is obtained, the arithmetic circuit 4 is provided with logic such that the small section is determined to be a cloud. The arithmetic circuit 4 determines whether or not to consider.

By the judgment in the arithmetic circuit 4, the cloud distribution in the area of 11 pixels × m lines can be judged. The arithmetic circuit 4 holds the determination result for each small section in the determination result storage unit 4a. At this time, counter 2 (1)
The count value of each of .about.2 (n) is cleared by the control of the latch / clear control circuit 3.

The calculation of the cloud amount value for each small section in the arithmetic circuit 4 is performed by the timing control by the cloud amount calculation start / stop timing generating circuit 5. The cloud amount calculation start / stop timing generation circuit 5 is previously provided with a time table for holding the start and end times of the scanning operation by the optical sensor, and the cloud amount calculation start / stop timing generation circuit 5 is input in real time with data. The above timing control is performed by referring to the time table at the scan time.

The arithmetic circuit 4 stops the above-mentioned processing at the cloud amount calculation stop timing from the cloud amount calculation start / stop timing generation circuit 5, and one observation unit based on the determination result stored in the determination result storage unit 4a until that time. (1 scene) Calculate the total cloud amount.

That is, the arithmetic circuit 4 carries out an arithmetic operation for obtaining the ratio between the total number of small sections in one observation unit (one scene) and the number of small sections regarded as clouds. The calculation formula is the number of small sections regarded as clouds / the total number of small sections within one observation unit. Here, the total number of small sections in one observation unit = (l2 /
m) × n.

FIG. 2 is a diagram showing the range of one observation unit and the control timing in one embodiment of the present invention. The operation of the embodiment of the present invention will be described with reference to FIGS.

The comparator circuit 1 compares all the input data with the threshold value, and when it judges that the cloud exceeds the threshold value, it outputs that fact to the counters 2 (1) to 2 (n). The counters 2 (1) to 2 (n) count up at the time of input of the data determined by the comparison circuit 1 to be the clouds of the respective areas.

In other words, the counter 2 (1) stores up to l1 / n data from the scan start timing and m
Up to the line (hatched portion in FIG. 2 = small section), the counter 2 (2) is in charge of data from 1 + l1 / n to 2 (l1 / n) and m lines. Similarly, the counter 2 (n) is 1+ (l1 / n) (n-1) to l
In charge of up to 1 piece of data and up to m lines.

Therefore, when the data from the scan start timing to the m lines is input, the counter 2
In (1) to 2 (n), the count value of the data determined to be a cloud in each small section in charge is held in the area of 11 pixels × m lines.

Each of the counters 2 (1) to 2 (n) outputs the counting result to the arithmetic circuit 4 when the counting of the data determined to be a cloud is completed in each of the small sections in charge thereof. The arithmetic circuit 4 calculates the cloud amount value of the corresponding small section based on the counting result of each of the counters 2 (1) to 2 (n), and determines whether or not each of the n small sections is regarded as a cloud. To do.

The arithmetic circuit 4 holds the judgment result for each small section in the judgment result storage section 4a. At this time, each of the counters 2 (1) to 2 (n) has its count value cleared by the control of the latch / clear control circuit 3.

Next, each of the counters 2 (1) to 2 (n) counts the data discriminated as a cloud in the respective small sections from the (m + 1) th line, and the arithmetic circuit 4 operates in the same manner as the above processing. It is determined whether or not each of the n small sections from the (m + 1) th line is regarded as a cloud.

The processing operation of each circuit described above is performed from the cloud amount calculation start timing to the cloud amount calculation stop timing, that is, for one observation unit (one scene),
The calculation of the simulated cloud area in each small section in one scene is repeated.

The arithmetic circuit 4 stops the above processing operation at the cloud amount calculation stop timing from the cloud amount calculation start / stop timing generation circuit 5, and based on the judgment result stored in the judgment result storage section 4a, one observation unit (1 Calculate the cloud amount of the whole scene.

In this way, the range of one observation unit is (l2 /
m) × n number of small sections, calculate the cloud amount for each small section, and judge whether or not to consider the small section itself as a cloud based on the cloud amount. You can judge the spread area.

As a result, even in a situation where the cloud amount value is small, such as "streak clouds", but cannot be ignored as the cloud spread, it is possible to regard the cloud spread as a set of small sections determined to be clouds. A more accurate approximation of the cloud amount visually judged is possible. Therefore, the work of reviewing and correcting the automatic cloud amount evaluation result can be reduced, and the operational load can be reduced.

In addition, the image catalog generally describes cloud amount values in four divided scene sizes such as upper left / upper right / lower left / lower right, instead of a division unit which is generally only one scene. In this case, the determination result stored in the determination result storage unit 4a by timing control from the cloud amount calculation start / stop timing generation circuit 5 is divided into four corresponding to the four-division scene size, and the cloud amount is calculated for each area. By calculating, the cloud amount can be evaluated in the four-division scene. This can be applied to divisions of four or more.

[0035]

As described above, according to the present invention, there is provided an automatic cloud amount evaluation device for evaluating cloud amounts in a plurality of scan data obtained by a scanning operation of an optical sensor of an earth observation satellite and each consisting of a plurality of pixel data. , Pixel data is compared with a preset threshold value to determine whether or not the pixel data is a cloud, and the number of data determined to be a cloud is counted for each of n division units obtained by dividing scan data into n equal parts. At the same time, based on the counting result, it is judged whether each division unit of the scan data is a cloud or not, and the cloud amount within the preset observation range is calculated to review or correct the cloud amount evaluation result of the image catalog. And the operational load can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a range of one observation unit and control timing in one embodiment of the present invention.

[Explanation of symbols]

 1 Comparison Circuit 2, 2 (1) to 2 (n) Counter 3 Latch / Clear Control Circuit 4 Arithmetic Circuit 4a Judgment Result Storage Section 5 Cloud Amount Calculation Start / Stop Timing Generation Circuit

Claims (2)

(57) [Claims] 1. An automatic cloud amount evaluation device for evaluating cloud amount in a plurality of scan data, each of which is obtained by a scanning operation of an optical sensor of an earth observation satellite and is composed of a plurality of pixel data, the pixel data being preset with the pixel data. A discriminating means for comparing the pixel data with a threshold to discriminate whether or not the pixel data is a cloud, and the discriminating means for every n division units obtained by dividing the scan data into n equal parts (n is a positive integer). Counting means for counting the determined number of data, determination means for determining whether or not each division unit of the scan data is a cloud based on the counting result of the counting means, and each division unit of the scan data are obtained. An automatic cloud amount evaluation device, comprising: a calculation unit that calculates a cloud amount within a preset observation range from the determination result of the determination unit. 2. The holding means for holding the judgment result of the judging means for each observation range unit.
The automatic cloud amount evaluation device described.