NDVI product registration method and device and computer system

Abstract

The invention discloses an NDVI (normalized difference vegetation index) product registration method and device and a computer system, which solve the problems of splicing and registration of NDVI products at different time and in different spaces, and comprises the following steps of: checking the quality of a space-time tile image, and removing tiles of which the cloud amount exceeds a threshold value, is not full and has no near-infrared band; the NDVI is calculated by using the near-infrared band and the red band of the tile image after the quality inspection, and an NDVI product is obtained; layering the NDVI products according to a time sequence, and splicing the adjacent NDVI products in each layer; and carrying out registration on the spliced NDVI product to obtain a seamlessly aligned NDVI product.

Description

Technical Field

[0001] The present invention relates to the application field of vegetation index products, and in particular to an NDVI registration method, device and computer system. Background Art

[0002] Vegetation information affects the balance of the global ecosystem and plays an important role in climate, hydrology and ecological cycles. In view of the important role of vegetation information in the global ecosystem, all countries are paying close attention to the changes in the earth's vegetation. At present, vegetation information monitoring based on satellite remote sensing is the most commonly used method. Satellites can obtain remote sensing information in the shortest time and in the widest range through images taken in space, which includes vegetation information. Therefore, how to extract this vegetation information from remote sensing images has become a very worthy research task.

[0003] Based on the spectral characteristics of the vegetation index of satellite remote sensing images, the spectral values ​​of the visible light band and the near-infrared band observed by remote sensing images are combined and calculated to obtain the vegetation index. It is a simple and effective empirical measurement of the surface vegetation status. After continuous exploration and research by scholars at home and abroad, more than 40 vegetation indices have been developed so far, and they are widely used in the fields of land vegetation cover change, crop yield forecast, regional drought monitoring, surface biophysical parameter calculation, global ecosystem research, etc. Among these vegetation indices, the Normalized Difference Vegetation Index (NDVI) is the most widely used vegetation index at present. It is not only easy to calculate, but also can eliminate most of the effects related to sensor radiation calibration, terrain, atmospheric conditions and observation angles, and enhance the sensitivity to vegetation. After more than 20 years of research, it has accumulated rich research results, making it very effective in the research and application of ground vegetation cover. Summary of the invention

[0004] The present invention proposes an NDVI product registration method and system, which solves the problem of splicing and registration of NDVI products in different time and space.

[0005] First, a registration method for NDVI products is proposed, including: quality checking of spatiotemporal tile images, removing tiles with cloud cover exceeding a threshold, incomplete coverage, and no near-infrared band; calculating NDVI using the near-infrared band and red band of the tile image to obtain NDVI products; stratifying NDVI products in time sequence and splicing adjacent NDVI products of each layer; and registering the spliced ​​NDVI products to obtain seamlessly aligned NDVI products.

[0006] In the second aspect, a NDVI product registration device is proposed, including: a preprocessing module, which is configured to perform quality checks on spatiotemporal tile images, and remove tiles with cloud cover exceeding a threshold, incomplete width, and no near-infrared band; an NDVI calculation module, which is configured to calculate NDVI using the near-infrared band and red band of the tile image to obtain an NDVI product; a stitching module, which is configured to layer the NDVI products in time sequence and stitch adjacent NDVI products of each layer; and a registration module, which is configured to register the stitched NDVI products to obtain a seamlessly aligned NDVI product.

[0007] In the third aspect, a computer system is proposed, comprising: a processor; a memory, comprising one or more computer program modules; wherein the one or more computer program modules are stored in the memory and configured to be executed by the processor, and the one or more computer program modules include instructions for implementing the NDVI product registration method.

[0008] In a fourth aspect, a computer-readable storage medium is proposed for storing non-transitory computer-readable instructions, characterized in that when the non-transitory computer-readable instructions are executed by a computer, the NDVI product registration method can be implemented.

[0009] In some examples, the layered NDVI products are aligned according to whether there is a reference NDVI product. When there is no reference NDVI product, the information entropy of each layer of the NDVI products after the stitching is calculated, and the NDVI product with the largest information entropy is selected as the reference NDVI product to align other NDVI products. When there is a reference NDVI product, the reference NDVI product is used to align other NDVI products.

[0010] The present invention has the following advantages: (1) multiple NDVI products are spliced ​​into one NDVI product, which reduces the computational complexity and improves the registration accuracy; (2) in the absence of reference data, the present invention can still register the NDVI products of spatiotemporal tiles. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a flow chart of a NDVI product registration method / system according to an embodiment of the present invention.

[0012] Figure 2 This is an NDVI result diagram of an embodiment of the present invention; wherein, (a) the red light band and the near infrared band in the original tile, and (b) the NDVI product.

[0013] Figure 3It is a layered spliced ​​NDVI product of an embodiment of the present invention; wherein, (a) the out-of-control NDVI product, (b) the NDVI product divided by time series, and (c) the NDVI product after each layer is spliced.

[0014] Figure 4 This is the NDVI registration result when there is no reference data in the embodiment of the present invention.

[0015] Figure 5 This is the NDVI registration result when there is reference data in the embodiment of the present invention. DETAILED DESCRIPTION

[0016] Figure 1 This is a flow chart of the NDVI product registration method. Figure 1 As shown, the present invention calculates NDVI using the near-infrared band and red band of the time series tile, and registers the NDVI products according to whether there is reference data: when there is reference data, the reference NDVI is used to register the NDVI products; when there is no reference data, the information entropy of the NDVI is calculated, and the NDVI with the largest information entropy is selected to register other NDVI products. The method is described in detail below.

[0017] Step 1: Check the quality of the spatiotemporal tile images and remove tiles with large cloud cover, incomplete coverage, and no near-infrared band. For example, tiles with cloud cover exceeding 10% can be removed.

[0018] Step 2: Calculate the Normalized Difference Vegetation Index (NDVI) using the near-infrared and red bands of the tile. The calculation formula is as follows:

[0019]

[0020] Among them, NIR represents the reflectivity of the near-infrared band, and RED represents the reflectivity of the red band.

[0021] Figure 2 is a NDVI result map; Figure 2 (a) is the red light band and near infrared band in the original tile. Figure 2 (b) is the NDVI product.

[0022] Step 3: Layer the NDVI in time sequence and splice adjacent NDVI products of each layer to obtain seamless NDVI products of each layer.

[0023] Figure 3 It is a layered spliced ​​NDVI product, in which: Figure 3 (a) is the out-of-control NDVI product, Figure 3 (b) NDVI products after stratification by time series, Figure 3 (c) is the NDVI product after stitching each layer. Figure 3 (b) and 3(c) have 5 NDVI products: (1), (2), (3), (4), and (5).

[0024] Step 4: Register the spliced ​​NDVI to obtain a seamless, high-precision aligned NDVI product.

[0025] Step 4.1: Align the NDVI after layering and stitching according to whether there is reference data.

[0026] (1) No reference data

[0027] Calculate the information entropy of each layer of NDVI after splicing. Information entropy indicates the average amount of information contained in the image. The larger the entropy value, the more information it contains. The calculation formula of information entropy is as follows:

[0028]

[0029] Among them, p(x i ) represents the random event X is x i probability.

[0030] For example, Figure 3 The three images in (c) are exactly equal to the 3×3 spliced ​​NDVI information entropy calculation, and the corresponding entropy values ​​are as follows:

[0031] (2) (3) (5) Information Entropy 0.6409 1.6615 0.8903

[0032] According to the entropy value calculated in the previous step, the NDVI with the largest information entropy is selected as the reference NDVI data, and other NDVIs are aligned with it.

[0033] For example, Figure 3 In (c), the NDVI product (3) is used as a reference to align the other four NDVIs. The alignment results are shown in Figure 2. Figure 4 As shown, it can be found that the alignment effect of the same object is greatly improved after registration.

[0034] (2) Reference data

[0035] Use the reference NDVI to align other NDVI products. Figure 5 It is an NDVI registration result when there is reference data.

[0036] The process of NDVI product registration is as follows:

[0037] First, the SIFT method is used to extract and match the same-name points of the reference NDVI and the NDVI to be aligned;

[0038] Then, the same-name points are used to perform geometric transformation on the NDVI feature points to be registered, and the registration is achieved by geometric polynomial correction. The formula is as follows:

[0039]

[0040] Among them, a i and b i are polynomial coefficients, (x, y) are image row and column coordinates, i = 0, 1, 2, and (X, Y) represent the corrected coordinates.

[0041] The present invention also provides an embodiment of an NDVI product registration device, which comprises a preprocessing module, an NDVI calculation module, a splicing module and a registration module.

[0042] The preprocessing module is configured to perform a quality check on the spatiotemporal tile images and remove tiles with cloud cover exceeding a threshold, insufficient coverage, and no near-infrared band. For example, tiles with cloud cover exceeding 10% can be removed.

[0043] The NDVI calculation module is configured to calculate the NDVI using the near infrared band and the red band of the tile image to obtain the NDVI product. The calculation formula refers to formula (1) in step 2.

[0044] The stitching module is configured to layer the NDVI products in time sequence and stitch adjacent NDVI products in each layer.

[0045] The registration module is configured to register the spliced ​​NDVI products to obtain seamlessly aligned NDVI products. The specific registration method of the registration module is shown in step 4.

[0046] The present invention also provides an embodiment of a computer system. The computer system includes a processor and a memory. The memory is used to store non-transitory computer-readable instructions (e.g., one or more computer program modules). The processor is used to run the non-transitory computer-readable instructions, and when the non-transitory computer-readable instructions are run by the processor, one or more steps in the NDVI product registration method described above can be executed. The memory and the processor can be interconnected through a bus system and / or other forms of connection mechanisms.

[0047] For example, the processor may be a central processing unit (CPU), a graphics processing unit (GPU), or other forms of processing units with data processing capabilities and / or program execution capabilities. For example, the central processing unit (CPU) may be an X86 or ARM architecture, etc. The processor may be a general-purpose processor or a special-purpose processor, and may control other components in the computer to perform desired functions.

[0048] For example, the memory may include any combination of one or more computer program products, and the computer program product may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. Volatile memory may include, for example, random access memory (RAM) and / or cache memory (cache), etc. Non-volatile memory may include, for example, read-only memory (ROM), hard disk, erasable programmable read-only memory (EPROM), compact disc read-only memory (CD-ROM), USB memory, flash memory, etc. One or more computer program modules may be stored on the computer-readable storage medium, and the processor may run one or more computer program modules to implement various functions of the computer.

[0049] The present invention also provides a computer-readable storage medium for storing non-transitory computer-readable instructions. When the non-transitory computer-readable instructions are executed by a computer, one or more steps in the above-mentioned NDVI product registration method can be implemented. When the NDVI product registration method and device provided by the embodiment of the present invention are implemented in the form of software and sold or used as an independent product, they can be stored in a computer-readable storage medium. For the relevant description of the storage medium, please refer to the corresponding description of the memory in the computer system above, which will not be repeated here.

Claims

1. A NDVI product registration method, characterized in that: include: Perform quality checks on spatiotemporal tile images and remove tiles with cloud cover exceeding the threshold, incomplete coverage, and no near-infrared band; Calculate NDVI using the near infrared band and red band of the tile image after quality inspection to obtain the NDVI product; Layer the NDVI products in time sequence and splice the adjacent NDVI products of each layer; The spliced ​​NDVI products are registered to obtain seamlessly aligned NDVI products.

2. The NDVI product registration method according to claim 1, characterized in that: The layered and spliced ​​NDVI products are aligned according to whether there is a reference NDVI product.

3. The NDVI product registration method according to claim 2, characterized in that: When there is no reference NDVI product, the information entropy of each layer of the spliced ​​NDVI products is calculated, and the NDVI product with the largest information entropy is selected as the reference NDVI product to align other NDVI products.

4. The NDVI product registration method according to claim 2, characterized in that: When a reference NDVI product is available, use it to align other NDVI products.

5. The NDVI product registration method according to claim 2, characterized in that: The SIFT method is used to extract and match the same-name points of the reference NDVI product and the NDVI product to be registered. The same-name points are used to perform geometric transformation on the feature points of the NDVI product to be registered to achieve registration. The formula for geometric transformation is: Among them, a i and b i are polynomial coefficients, i=0,1,2, (x,y) are the row and column coordinates of the image, and (X,Y) represents the corrected coordinates.

6. A NDVI product registration device, characterized in that: include: A preprocessing module, which is configured to perform a quality check on the spatiotemporal tile images and remove tiles with cloud cover exceeding a threshold, insufficient coverage, and no near-infrared band; An NDVI calculation module is configured to calculate NDVI using the near infrared band and the red band of the tile image after quality inspection to obtain an NDVI product; A splicing module, which is configured to layer the NDVI products in time sequence and splice adjacent NDVI products of each layer; The registration module is configured to register the stitched NDVI products to obtain seamlessly aligned NDVI products.

7. The NDVI product registration device according to claim 6, characterized in that: The layered and spliced ​​NDVI products are aligned according to whether there is a reference NDVI product: When there is no reference NDVI product, calculate the information entropy of each layer of the spliced ​​NDVI products, select the NDVI product with the largest information entropy as the reference NDVI product, and align the other NDVI products; When a reference NDVI product is available, use it to align other NDVI products.

8. The NDVI product registration device according to claim 7, characterized in that: The SIFT method is used to extract and match the same-name points of the reference NDVI product and the NDVI product to be registered. The same-name points are used to perform geometric transformation on the feature points of the NDVI product to be registered to achieve registration. The formula for geometric transformation is: Among them, a i and b i are polynomial coefficients, i=0,1,2, (x,y) are the row and column coordinates of the image, and (X,Y) represents the corrected coordinates.

9. A computer system, characterized in that: include: processor; a memory including one or more computer program modules; Wherein, the one or more computer program modules are stored in the memory and configured to be executed by the processor, and the one or more computer program modules include instructions for implementing the NDVI product registration method described in any one of claims 1-5.

10. A computer-readable storage medium for storing non-transitory computer-readable instructions, characterized in that: When the non-transitory computer-readable instructions are executed by a computer, the NDVI product registration method according to any one of claims 1 to 5 can be implemented.

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