Introduction and differentiation of 4D products (DLG, DEM, DOM, DRG)

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What are 4D products (DLG, DEM, DOM, DRG)?

4D products refer to DRG (digital raster map), DLG (digital wireframe), DEM (digital elevation model), DOM (Digital ortho image). 4D Composite product is a combination of any two or several product models in 4D products, generated by the fusion method of the superimposed products.

1. DRG (Digital raster map)
  
Digital raster maps are digital products in grid form of paper topographic maps. It can be used as a background to relate to other spatial information, for data collection, evaluation and update, and to derive new visual information from DOM and DEM integration.

2. DLG (digital line map)
  
vector datasets for tiered storage of basic geographic features on existing topographic maps. The digital line drawing includes both spatial information and attribute information, which can be used in all aspects of construction planning, resource management, investment environment analysis, as well as the spatial positioning basis of various professional information systems, such as population, resources, environment, traffic, security and so on.

3. DEM (digital elevation model)
  
A digital elevation model is a set of numbers that represent the undulating patterns of the ground in elevation. Can make the perspective, the sectional view, carries on the engineering earthwork calculation, the surface coverage area statistic, uses for with the elevation related landform morphological analysis, the pass-Sight condition analysis, the flood inundation area analysis.

4. DOM (Digital ortho image)
  
Using aerial photographs and remote sensing images, the image data generated by the image is trimmed according to the range of images. Its information is rich and intuitive, with good interpretation and measurable, which can directly extract the natural geography and socio-economic information.

the difference between the DOM DEM DLG DRG Digital ortho Image (digitally orthophoto map abbreviation DOM)Digital Elevation Model (DEM) is used to scan the digitized aerial photograph, the projection error is corrected by pixel-by-cell, mosaic, and the image data set generated by the national basic scale topographic map is clipped. It is an image with the geometric precision and image features of the map, which has the advantages of high precision, rich information and real-time visualization.
Digital Elevation model abbreviation DEMIs the data set of the planar coordinates (x, y) and elevation (Z) of the regular grid on a projection plane, such as a Gaussian projection plane. The grid spacing of a dem should be adapted to its elevation accuracy and form a regular grid series. According to the different elevation accuracy, can be divided into different types. To fully reflect the surface morphology, the data of discrete elevation points can also be added.
Digital Line Map (Graphic abbreviation DLG)is the vector data set of the existing topographic map elements, preserving the spatial relation and related attribute information among the features, and comprehensively describing the surface targets.
Digital Raster Map (digitally Raster Graphic abbreviation DRG)is a raster data file obtained by computer processing of existing paper topographic maps. After scanning digitization, each topographic map is corrected by geometry, and the content is updated and data compression is processed, and the color topographic map should be corrected by color, so that the color of each image is basically consistent. Digital raster maps are consistent with national basic scale topographic maps on content, geometric accuracy, and color.

Introduction and differentiation of 4D products (DLG, DEM, DOM, DRG)

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