4d is DEM, DTM, DSM, and Dom respectively. Next we will give a brief introduction to them.
Brief Introduction:
DEM
- Digital Elevation Model
- Digital Elevation Model
- A physical ground model that uses a set of ordered numeric arrays to represent the ground elevation. It is a branch of a digital terrain model.
DTM
- Digital Elevation Model
- Digital Terrain Model
- Represent the spatial distribution of actual terrain features in the form of digits
DSM
- Digital Surface Model
- Digital Surface Model
- A set of objects whose surface shapes are expressed in numbers. In addition to natural terrain, it also includes buildings, vegetation, roads, and other elements.
Dom
- Digital orthophoto map
- Digital normal image
After a brief introduction, let's take a look at the relationships between them.
Digital Elevation Model and digital terrain modelFrom the mathematical perspective, the elevation model is a continuous function of the elevation Z on the plane x and y independent variables. The Digital Elevation Model (DEM) is only a finite discrete representation of it. The most common expression of an elevation model is the altitude relative to the sea level or the relative height of a reference plane. Therefore, an elevation model is also called a terrain model. In fact, terrain models not only contain elevation attributes, but also other surface morphology attributes, such as slope and slope. A digital terrain model is a digital expression of information about the terrain surface. It is a digital combination of spatial location features and topographic attribute features. A digital elevation model is used when the terrain attribute is an elevation. An elevation is the third coordinate in a geographical space. Because the data structure of the traditional geographic information system is two-dimensional, the establishment of the digital elevation model is a necessary supplement. DEM is usually expressed by the elevation matrix of the grid element with the rule of the earth surface. The generalized DEM also includes contour lines, triangular networks, and other numerical representations of all the expressions of the elevation. In geographic information systems, dem is the basic data for DTM. Other terrain elements can be exported directly or indirectly by DEM, which is called "Derived Data", such as slope and slope. Reference: digital terrain model
Digital Elevation Model and digital Surface ModelCompared with DSM, dem only contains the elevation information of the terrain, and does not contain other land information. Based on DEM, DSM further covers the elevation of ground information other than ground.
Traditional Dom and real domConventional Dom acquisition is based on the digital elevation model DEM in digital differential correction. The real Dom is obtained based on the digital surface model DSM during digital differential correction.
Images and truth
