4d technology details and Application Research

Digital Elevation Model (DEM) is a plane coordinate (x, y) and elevation (z) of grid points on a certain projection plane (such as a Gaussian projection plane). The grid interval of DEM should adapt to its elevation precision and form a grid series with rules. Different types of elevation precision are available. To fully reflect the form of the earth surface, you can also add discrete time points.
Digital Line Graphic (DLG) is a vector dataset of the existing topographic map elements. It stores the spatial relationship between each element and relevant attribute information to fully describe the surface target.
Digital Raster Graphic is a raster data file generated after the existing paper topographic map is processed by a computer. After each topographic map is scanned and digitalized, It is corrected by ry, And the content is updated and the data is compressed. The Color Topographic Map should also be color corrected so that the colors of each image are basically the same. The content, geometric precision, and color of the digital raster map are consistent with those of the national basic scale topographic map.
Digital orthophoto map (DOM) is a digital aerial image that is scanned and processed using a digital elevation model (DEM). The digital projection difference is corrected and embedded by pixel, the Digital Direct image dataset generated based on the GIS range of the national basic scale topographic map. It is an image with both map geometric precision and image features, and has the advantages of high precision, rich information, intuitive and true.