4D Products in GIS (DLG, DRG, DEM, DOM)

DLG

Digital line Map (DLG, digital lines Graphic): is a vector dataset of map features that are basically consistent with existing line strokes, and preserves spatial relationships and related attribute information between features.

In the Living Word map, the most common product is the digital line map, the final result of the external industry mapping is the DLG. The product describes the surface phenomenon more comprehensively, the visual effect is consistent with the same scale but richer in color. This product satisfies a variety of spatial analysis requirements, can randomly choose and display data, and other information overlay, can carry out spatial analysis, decision-making. Some of the core elements of the terrain can be used as the line-zoned topographic elements in the digital Ortho image topographic map. Digital line drawing dlg.jpg.

Digital line Map (DLG) is a more convenient way to enlarge, roam, query, check, measure, overlay map. Its data volume is small, easy to layer, can quickly generate thematic maps, so also known as vector Thematic information DTI (Digital thematic information). This data can meet the various spatial analysis requirements of GIS and be considered as intelligent data. Data can be randomly selected and displayed, and several other products superimposed, easy to analyze, decision-making. The technical characteristics of the digital line map (DLG) are as follows: Map geographic content, distribution, projection, precision, coordinate system and the same scale map. The graphics output is in vector format, and any scaling is not deformed.

Production Technology raw materials are mainly used: data collection, aerial film, high-resolution satellite, topographic maps and so on. Production method:

1) Digital photogrammetry, three-dimensional tracking three-dimensional mapping. At present, the domestic digital photogrammetry software Vintuozo system and the jx-4c DPW system all have the corresponding vector graph system, and their precision index is higher. The Vintuozo system has two versions of workstation and NT, while the JX-4C DPW system has only one NT version.

2) analytic or computer-assisted digital mapping. This method is to obtain DLG data by stereo mapping of aerial and high resolution films on the analytic mapping instrument or simulator. This method also requires the use of GIS or CAD graphics processing software, the data obtained to edit, and ultimately produce results data.

3) on the existing topographic map scanning, human-computer interaction will be vectorization of its elements. At present, vectorization software or GIS and CAD software used at home and abroad use vectorization function to vectorize scanned image and transfer it into corresponding system.

4) on the newly produced digital ortho Image, the manual tracking of the frame elements is digitized. On-screen tracking: You can use CAD or GIS and Virtuozo software to insert the ortho image into the workspace at a certain scale, and then perform the corresponding feature acquisition on the diagram.

5) field test map.    (See the basic Process section of digital mapping) the application of digital line mapping in land use planning and control, the selection of shopping malls, factories, transportation hubs, urban construction management, agricultural climate zoning, environmental engineering, air pollution monitoring, road traffic construction and management. Natural disasters, war disasters, other disasters monitoring and estimating natural resources, human resources, geomorphology changes in the livelihood industry (medical, public utilities, services, etc.).

Dem

Digital Elevation Model, abbreviated DEM, is a data set of the plane coordinates (x, y) and its elevation (Z) of the regular grid in a certain range, and it mainly describes the spatial distribution of the topography of the region. are data acquisition (including sampling and measurement) by contour or similar stereoscopic models, which are then formed by interpolation. Dem is a virtual representation of the topography, can be derived from contour lines, slope maps and other information, but also with the DOM or other thematic data overlay, for the analysis of terrain-related applications, and it itself is to make the basic data of the DOM.

A dem is a set of ordered values Dem is a kind of solid ground model representing ground elevation by a set of ordered numerical array, which is a branch of digital terrain model, or DTM. It is generally believed that DTM is a spatial distribution of linear and nonlinear combinations that describe various geomorphic factors including elevation, such as slope, slope direction, slope change rate, and so on, in which DEM is a simple single digital landform model of 0 order, and other geomorphic characteristics such as slope, slope direction and slope change rate can be derived from Dem. The other two branches of DTM are the numerical models of various non-geomorphic properties expressed in matrix form, including the natural geographical elements and the socio-economic and human factors related to the ground, such as soil type, land use type, rock depth, land price, commercial dominance area and so on. In fact, DTM is one of the raster data models. The difference between it and the raster representation of an image is that the image is a single point representing the properties of the entire cell, whereas in the DTM, the grid points represent only the attributes of the point, and the attributes between the points and points can be obtained by interpolation.

There are many ways to set up Dem from data Sources and collection methods: (1) direct measurement from the ground, such as GPS, Total station, field measurement, etc. (2) according to aerial or space imagery, through photogrammetry, such as stereo coordinate instrument observation and air three encryption method, analytic mapping, Digital photogrammetry and so on, (3) from the existing topographic map collection, such as grid reading point method, digital instrument handheld tracking and scanner semi-automatic acquisition and then through interpolation to generate Dem and other methods. There are many methods of DEM interpolation, there are three kinds of interpolation, partial interpolation and single point shifting. At present, the algorithm is used to establish irregular triangular network (triangular irregular network, or tin) through contour and elevation points. The DEM is then built on a tin based on linear and bilinear interpolation.

As the DEM describes the ground elevation information, it is widely used in surveying, hydrology, meteorology, geomorphology, geology, soil, engineering construction, communication, meteorology, military and other national economy and national defense construction as well as humanities and natural science fields. such as in engineering construction, can be used for such as earthwork calculation, the analysis of the general view, in flood control and disaster reduction, DEM is the basis for hydrological analysis such as catchment area analysis, water network analysis, rainfall analysis, flood storage calculation, inundation analysis, etc. In the wireless communication, can be used for cell phone base station analysis and so on.

Drg

In terms of geography, DRG is the abbreviation for digital Raster graphic, which is called a numerical raster map: It is a raster dataset that is consistent with the topographic map in terms of content, geometrical accuracy and color, based on existing topographic maps such as paper, film, and geometric corrections and color correction.

Map by scanning, geometric correction, image processing and data compression processing, color map should be color correction, so that the color of the image is basically the same. The Digital raster map (DRG) is consistent with the same-scale topographic maps in content, geometric accuracy, and color. This product is a product of analog product transition to digital products, can be used as background reference image and other spatial information related reference and analysis. It can be used for data collection, evaluation and update of digital line map, and can be integrated with digital ortho image and digital elevation model, and derive new information and make new map. Digital Raster Diagram Drg.jpg

the technical characteristics of the digital raster map (DRG) are as follows: The geographical content of the map, the visual design and the same scale topographic map, the plane coordinate system is based on the 1980 XI ' an coordinates geodetic datum; The map projection adopts Gauss-gram gauss–krüger projection; The elevation system adopts 1985 national elevation datum. The image resolution is input greater than 400dpi, and the output is greater than 250dpi.

DRG can be used as a background for data reference or for fitting other geo-related information, to enable data collection, evaluation and update for digital line map (DLG), and to integrate with data information such as digital ortho image (DOM), digital elevation model (DEM). Derive new visual information to extract, update map data, and draw a paper map.

DOM

Digital Ortho Image (Dom,digitalorthophotomap): It is a digital ortho image set produced by digital differential correction and mosaic of aerial (or space) photograph, which is cropped according to a certain range of images. It is an image with both the geometric accuracy of the map and the image features.

Dom has the advantages of high precision, rich information, intuitive realism, quick access, can be used as a map to analyze background control information, and also can extract historical information or latest information from natural resources and socioeconomic development, and provide reliable basis for the prevention and treatment of disaster and public facilities construction planning. You can also extract and derive new information from the Implement the map revision update. Evaluating the accuracy, realism and completeness of other data is excellent. Hefei Digital Ortho image map dom.jpg.

the technical features of the graph are as follows: Digital orthographic image, map scale, projection, precision, coordinate system, consistent with the same scales, the image resolution is more than 400dpi, the output is greater than 250dpi. As the DOM is digital, can be locally developed amplification on the computer, with good interpretation performance and measurement performance and management performance, such as the use of rural land certification, the designation of the parcel boundary ratio and digital its point coordinates, land use survey and so on. Dom can be used as a separate background layer and place name, map of the kilometer grid, kilometer grid and other elements layer composite, production of various thematic maps.

production of the main technical methods: the use of aerial photographs or high-resolution satellite remote sensing image data. Using: 1) Vintuozo system digital photogrammetry workstation. The Vintuozo system can improve the accuracy of the DOM by using the detection and editing of DEM. It can also be used to perform gray-scale connection between pictures and pictures to ensure consistency of image tones. 2) Adopt JX-4DPW system. JX-4DPW is a set of digital photogrammetry systems based on WindowsNT. Because of its editing of DEM is a single point of editing, and the system also has the function of 0 stereo check of DOM, so its DOM precision is high. The single-chip digital differential correction Vintuozo system based on DEM has the module of single-chip digital differential correction.

Application of Digital ortho image map flood monitoring, river change, drought monitoring, agricultural yield estimation (precision agriculture), land cover and dynamic monitoring of land use land resources, desertification monitoring and forest monitoring (forest pest), shoreline protection, ecological change monitoring.

The advantages of DOM are mainly expressed in : ease of use, when using the DOM, all the XML document information will be stored in memory, and the traversal is simple, support XPath, enhanced ease of use. The main disadvantages of DOM are: low efficiency, slow parsing, high memory consumption, and almost impossible to use for large files. In addition, low efficiency also manifests itself in a significant amount of time spent, because when parsing using the DOM, an object is created for each element, attribute, processing-instruction, and comment of the document. Thus, the creation and destruction of a large number of objects used in the DOM mechanism will undoubtedly affect their efficiency.

(GO) 4D products in GIS (DLG, DRG, DEM, DOM)