KR101731234B1

KR101731234B1 - Correction for radiance artefacts in spectral imagery acquired from satellite or aircraft platforms

Info

Publication number: KR101731234B1
Application number: KR1020160014222A
Authority: KR
Inventors: 박영제; 김원국; 조성익
Original assignee: 한국해양과학기술원
Priority date: 2016-02-04
Filing date: 2016-02-04
Publication date: 2017-05-02

Abstract

In the present invention, a marine payload image of a Chollian satellite or its successive satellite produces a single image by combining partial images. In a spectral image taken by a satellite or an aircraft, an artificial error is included in the radiance due to a misalignment, a ghost image, or a calibration error Therefore, it is a relatively simple radiance correction method using the information of the image itself by correcting the image of one side assuming a model in which the difference between the two measurements at the boundary is calculated and reduced according to the distance from the interface. The present invention relates to a method for correcting an inter-slot deviation of an image captured by a satellite or an aircraft, which has an effect of improving an accuracy of a satellite output by reducing an artificial error of the satellite.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting a deviation between images of an image taken on a satellite or an aircraft,

The present invention relates to a method for correcting an inter-slot deviation of an image photographed by a satellite or an aircraft. More specifically, an image taken by a satellite or an aircraft is corrected for the amount of light The present invention relates to a method for correcting inter-slot variation of an image photographed on such a satellite or an aircraft using a deviation model.

Geostationary Ocean Color Imager (GOCI), one of the world's first geostationary orbital ocean observing satellites, is one of the three payloads of Chollian launched in June 2010. Since then, it has been around Korea, Japan, and eastern China. It collects the color data of the ocean and monitors the marine environment almost in real time with the non-existent cycle (8 times a day during the day) resolution and the high spatial resolution by the ocean color sensor, and the export light quantity, chlorophyll concentration, , Amount of dissolved organic matter, red tide index, and so on.

The pointing mirror included in the GOCI first specifies an area to be a target and then obtains eight spectral channels and images of two dark signals through the rotation of the filter wheel.

However, the size of the metal oxide semiconductor detector included in the GOCI (1432 * 1415 pixels with a spatial resolution of 500 m) is detected at the same time as the target area (2500 km * 2500 km around 130 ° E and 36 ° N) So that the regions to be targeted can be spatially arranged in 4x4 blocks by 16 serial arguments as shown in Fig.

The area included in each block is referred to as a slot, and images of 16 slots are registered as one level 1A. However, 16 slots are shot with 8 bands for 30 minutes and then joined to one full image, so discontinuity appears in the overlapping edges of several slots. The inter-slot boundary difference is called a ISRD (Inter-Slot Radiometric Discrepancy). The inter-slot boundary difference is caused by natural factors such as the amount of solar light per slot, This is caused by a combination of anthropogenic factors.

However, there is a problem that it is difficult to correct the deviation due to the stray light generated in the spatial range varying with time and position, depending on the reflectance near the bright portion such as the cloud or the ground in the boundary between the slots.

Korean Patent Registration No. 10-1484671 Korean Patent Application Publication No. 10-2014-0047980

An object of the present invention is to calculate a difference measured at an interface between a slot and a slot and to correct one partial image so that the image itself can be corrected when the influence of the cloud on the boundary is small and the spatial variation of the deviation is small.

As means for solving the above-mentioned problems, in the embodiment of the present invention, a method of registering images of 16 slots collected from a GOCI as one level 1B; A band collecting step of collecting frequency bands formed between two adjacent slots in the horizontal and vertical directions in the sixteen slots; A slot for determining an inter-slot boundary difference by using frequency bands collected in two adjacent slots in the horizontal or vertical direction and correcting an image by changing one band at two wavelengths generated in a boundary between two slots And an inter-boundary-difference correcting step.

The bands calculated between two neighboring slots in the horizontal direction include high variability depending on the region, the bands indicating high rate of change include 6 and 8, and the bands showing low rate of change include 1 and 2 .

The bands calculated between two neighboring slots in the vertical direction include a small variation depending on the region, the band 1 is less variable, and the band 6 is characterized in that the variability is increased.

As a preferred embodiment of the present invention, the inter-slot deviation correction method is performed by using RGB (red, green, blue) of upper atmosphere and RGB (red, green, blue) of lower atmosphere and all other wavelengths, So that only one of the wavelengths of one wavelength can be corrected.

According to the present invention, the following effects can be achieved by this configuration.

It is possible to correct an artificial radial luminance deviation caused by various reasons by using overlapping photographed portions of an image photographed by a satellite or an airplane, and it is possible to compensate for not only a duplicated photographed portion but also other regions I have.

FIG. 1 is a view schematically showing an area taken by a Cheonanian marine observation satellite,
FIG. 2 is a diagram schematically showing a picture (left) in which 16 slots images are registered as one level 1B and an area occupied by each slot according to an embodiment of the present invention,
FIG. 3 is a diagram schematically illustrating a difference in radiant amount of each band in an overlapped portion between adjacent slots in the horizontal direction according to an embodiment of the present invention, and FIG.
FIG. 4 is a diagram schematically illustrating a difference in radiant amount of each band in an overlapped portion between adjacent slots in a vertical direction according to an embodiment of the present invention,
5 is a diagram schematically illustrating that a difference in radiant luminance at a slot boundary increases according to a location of a bright radiant intensity RPT in a north region of a slot boundary according to an exemplary embodiment of the present invention,
6 to 7 are views showing images before and after the slot boundary difference correction according to an embodiment of the present invention.

Hereinafter, a method of correcting an inter-slot deviation of an image photographed by a satellite or an aircraft according to the present invention will be described in detail with reference to the accompanying drawings. It is to be noted that like elements in the drawings are represented by the same reference numerals as possible. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

FIG. 1 is a view schematically showing an area photographed by a Cheonanian marine observation satellite. FIG. 2 is a view illustrating an image of 16 slots registered as a level 1B according to an embodiment of the present invention. FIG. 3 is a view schematically showing the difference in radiant amount of each band in the overlapped portion between adjacent slots in the horizontal direction according to an embodiment of the present invention, and FIG. 3 FIG. 5 is a diagram illustrating a difference in radiant amount of each band in an overlapped portion between adjacent slots in a vertical direction according to an exemplary embodiment of the present invention. FIGS. 6 to 7 are views schematically showing that when a bright radiant luminance RPT occurs, a difference in radiant luminance at a slot boundary is increased according to a position thereof. FIGS. According to the example diagram showing an image before and after the slot boundary difference correction.

The present invention is characterized in that it comprises the steps of: registering images of 16 slots collected from the GOCI as one level 1B; calculating bands at the boundaries of slots adjacent horizontally in the 16 slots; Lt; RTI ID = 0.0 > inter-slot boundary difference < / RTI >

In the step of registering with the level 1B, the image of 16 slots taken by the GOCI is registered as one level 1B. The slot-based image is stored as a rectangular image with a size of 1413 * 1430 pixels. The slot image is not based on a specific spatial coordinate system because it contains the earth as it is photographed by the GOCI sensor. Therefore, in order to display 16 slot images in one unified spatial coordinate system, it is necessary to perform spatial coordinate conversion. In this case, a combined image of 16 slot images is referred to as a level 1B image. Level 1B images are based on an orthographic coordinate system. The spatial coordinate transformation between the slot image and the level 1B image is made up of the sum or product of the quadratic terms of the horizontal and vertical coordinates of the image, and has an individual polynomial coefficient for each slot. Using this polynomial, 16 slot images can be projected onto one level 1B image.

The band collecting step of the neighboring slots in the horizontal and vertical directions collects the frequency bands of neighboring slots. As shown in FIG. 3, neighboring slots, for example, slot 3 and slot 6, slot 4 And slot 5, slot 8 and slot 9, slot 7 and slot 10, and so on.

At this time, the spectral resolution is shown in Table 1.

channel Center wavelength (Band center (nm)) Bandwidth (nm) Signal to noise ratio (SNR) B1 412 nm 20 nm 1,000 B2 443 nm 20 nm 1,090 B3 490 nm 20 nm 1,170 B4 555 nm 20 nm 1,070 B5 660 nm 20 nm 1,010 B6 680 nm 10 nm 870 B7 745 nm 20 nm 860 B8 865 nm 40nm 750

Referring to Table 1, when the band exhibiting high variability is examined, bands 6 and 8 have the strongest variability, bands 1 and 2 have no variability, bands 3, 4, 5 and 7 are medium, Band 7 shows the least variability.

The band collecting step of the vertically neighboring slots collects frequency bands of neighboring slots, and displays regions and bands having low variability. As shown in FIG. 4, the neighboring slots calculate the bands of consecutive slots by using slots 3 and 4, slots 8 and 7, slots 7 and 6, and the like. At this time, the band with the lowest variability is 1, the band with high variability is 6, and the band with the lowest variability is less than 1%.

As described above, the cause of the difference between the slots is determined by confirming the variability extracted from the bands of the vertically and horizontally neighboring slots, and the slot-to-slot boundary difference can be generated due to the cloud, stray light, and signal calibration error of the sensor 5).

In the step of correcting the inter-slot boundary difference, when it is determined that the influence of the cloud on the boundary is small and the spatial variation of the variation is small according to the variability extracted from the band of the slot, the distance from the boundary by the color composite data of GOCI Assuming a reduced model, the image of one side is corrected.

6 to 7, images assigned to the red (R), green (G), and blue (B) wavelength bands are transmitted to a top-of-atmosphere (TOA) ), And corrects the image excluding RGB, so that the difference between the slots can be minimized.

Therefore, the present invention measures Inter-Slot Radiometric Discrepancy (ISRD) between adjacent slots in the horizontal and vertical directions using measured values overlapped in 16 overlapping slots of GOCI, In particular, assuming that the upper end of the lower slot has a deviation value, the radiated deviation due to the misfit can be quantified at the slot boundary, because the deviation due to the random light is greatest at the lower end of the upper slot among the slots adjacent to each other in the vertical direction. Assuming that the deviation due to the fluctuating light is linearly decreased toward the upper end of the slot and is reduced at a certain rate and that the influence of the random light disappears at a certain distance from the lower end, The effect can be achieved.

While the applicant has described various embodiments of the present invention, it is to be understood that such embodiments are merely exemplary embodiments of the technical idea of the present invention, and that any changes or modifications as far as implementing the technical idea of the present invention are within the scope of the present invention .

Claims

Registering images of 16 slots collected from the GOCI as one level 1B;
A band collecting step of collecting frequency bands formed between two adjacent slots in the horizontal and vertical directions in the sixteen slots;
A slot for determining an inter-slot boundary difference by using frequency bands collected in two adjacent slots in the horizontal or vertical direction and correcting an image by changing one band at two wavelengths generated in a boundary between two slots A boundary boundary difference correction step;
And correcting an inter-slot deviation of an image photographed on a satellite or an aircraft.

The method according to claim 1,
The bands calculated between two adjacent slots in the horizontal direction include high variability depending on the region,
The bands indicating a high rate of change include 6 and 8,
And a band having a small rate of change includes 1 and 2. 2. The method of claim 1,

The method according to claim 1,
The band calculated between two adjacent slots in the vertical direction includes a small variation depending on the region,
Wherein band 1 is less variable and band 6 is increased in variability.

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The method according to claim 1,
The inter-slot deviation correction method uses the wavelengths of RGB (red, green, blue) and upper and lower atmospheres of RGB (red, green, blue) in the upper atmosphere and corrects the wavelengths of both wavelengths in one And correcting only the slot of the at least one slot.