主权项 |
1. A method of compensating for atmospheric events in satellite images, comprising:
receiving image data representing an image of at least a portion of the Earth based on the radiance received by a sensor on the satellite, wherein the image data is pixelated and each pixel represents light directed along a path from a target region on the Earth to the sensor, with other portions on the Earth being non-target regions; receiving Earth coordinate data related to the image data for the image; receiving temporal data related to the image data for the image; retrieving one or more atmospheric characteristics from a database, the retrieving being based on the earth coordinate data and the temporal data; processing the image data for the image to determine Aerosol Optical Depth for the image, without using image data from another image; and converting the image from radiance to surface reflectance by using the determined Aerosol Optical Depth, including correcting for light that has been scattered at least a first time by the atmosphere onto one of the non-target regions and then reflected by the one of the non-target regions and then scattered at least a second time by the atmosphere onto the path to the sensor (C2); wherein the processing operation includes: assuming an Aerosol Optical Depth for at least a portion of the image; deriving a surface reflectance of the portion of the image from the Aerosol Optical Depth, the retrieved atmospheric characteristics, and the radiance received; calculating an expected radiance for at least the portion of the image based on the derived surface reflectance, the assumed Aerosol Optical Depth, and the retrieved atmospheric characteristics; comparing the expected radiance to the actual radiance received for at least the portion of the received image; and adjusting the Aerosol Optical Depth in a direction to bring the expected radiance closer to the actual radiance received; wherein the calculating, comparing, and adjusting operations are performed iteratively until the comparison shows the expected radiance to be within a predetermined threshold of the actual radiance received; wherein the image is used to derive both a radiance received for a target region of the image and a radiance received for a background region of the image; wherein the radiance received for the background region is derived by using a convolution filter for the region of the image proximate to the target region, in order to account for adjacency effects including light scattered by a plurality of different types of scattering pathways. |