4d Product Introduction

The Digital Elevation Model (DEM) is a dataset that rules grid dot plane coordinates (x, y) and Its elevation (z) on the Gaussian projection plane. The horizontal interval of DEM varies with the landform type. Products of different levels can be classified based on different elevation precision.

Digital orthophoto map (DOM) is a digital aerial photos/remote sensing photos (monochrome/color) scanned and processed using the digital elevation model, which is corrected by pixel, then, the image data is customized based on the image range. A general plan with a kilometer grid, interior/exterior decoration and annotation.

Digital Line Graphic (DLG) is a vector dataset of basic geographical elements on an existing topographic map, and stores spatial relationships and related attribute information between elements.

Digital Raster Graphic is a digital product of paper topographic maps. After each image is scanned, corrected, processed, and compressed, a grid file with the same content, geometric precision, and color as a topographic map is formed.