Geographic remote sensing problem

1, the spatial resolution refers to the minimum limit of the spatial geometric length of the identifiable critical object in the image, that is, the resolution of the fine structure. 2. Spatial resolution refers to the minimum distance between two adjacent features that can be identified in remote sensing images. For photographic images, it is usually expressed by the number of distinguishable black and white "line pairs" per unit length (line pairs/mm); For scanned images, instantaneous field of view (IFOV) is usually used to represent (milliradian mrad), that is, pixels are the smallest distinguishable areas in scanned images. The actual size of spatial resolution value on the ground is called ground resolution. For the photographic image, it is represented by the coverage width (m) of the line pair on the ground; For the scanned image, it corresponds to the actual ground size (m) of the pixel. For example, the spatial resolution or ground resolution of the multi-band scanned image of Landsat is 79 meters (pixel size is 56×79 m2). But the ground resolution with the same line pair width and pixel size is different. For an optically scanned image, it takes about 2.8 pixels to represent the same information in a line pair on a photographic image. Spatial resolution is one of the important indexes to evaluate sensor performance and remote sensing information, and it is also an important basis to identify the shape of ground objects. 3. The intuitive understanding of spatial resolution means that the critical geometric size of an object can be identified by instruments.

Spatial resolution

Spatial resolution is sometimes called geometric resolution or high contrast resolution in CT equipment, which refers to the ability to distinguish fine structures under high contrast, that is, the ability to display the smallest volume lesions or structures. When evaluating the quality of CT images, spatial resolution is often considered first. Because the detector of CT image has a certain size and the sampling distance is also certain, the spatial resolution of CT image is determined by the geometric size of the focus of X-ray tube, and basically has nothing to do with X-ray dose. In the case of a certain X-ray dose, there is a certain restriction between spatial resolution and density resolution, so it is impossible to improve spatial resolution and contrast resolution at the same time. There are many factors that affect the spatial resolution, including the aperture of the detector unit, the spatial sampling interval (every 360 samples), the form of convolution function, the pixel size of the reconstructed image, the focus size of the X-ray tube, the absorption coefficient m of the measured object and the system noise. To achieve high spatial resolution, it is necessary to control the above factors reasonably [1]? .