The grid consists of rows, columns and grid cells, where the rows and columns start from the upper left corner of the grid, the row direction is taken as the Y coordinate, and the column direction is taken as the X coordinate grid cell, which is defined by its column position. Raster data represents a point with a single grid cell, a line with a series of adjacent grid cells, and a surface with multiple sets of adjacent grids. Each grid cell has a value, which is an integer (representing category data, such as land use type) or a floating point (representing continuous data, such as precipitation). Each pixel value in the grid represents the characteristics of the spatial phenomenon in this position determined by the row and the column. The raster data model does not clearly separate spatial data from attribute data, so database management is of little use. The size of grid cells determines the resolution of grid data model; A large proportion of grid cells can't represent the exact location of spatial elements, while a smaller grid cell will increase the amount of data and data processing time.