The full from of DEM is Digital Elevation Model. Through Digital Elevation Model we represent ground surface topography data or terrain data. Digital Elevation Model is also known as Digital Terrain Model (DTM). LiDAR is a Remote Sensing technology or method. LiDAR collect highly accurate and dense points thoroughly from the surface or terrain. Collected sample points are representing height of a terrain. The points collected from LiDAR is highly accurate and dense which helps us to construct Digital Elevation Model (DEM). LiDAR can able to collect thousands of points in a seconds.
DEMs are generally built using Remote Sensing techniques or from land surveying. DEMs are generally used in Geographical Information System (GIS) for producing digital relief maps. Digital elevation model (DEM) along with Geographical Information System (GIS) techniques is to utilize design in urban areas.
LiDAR technologies is used to collect data from surface or terrain. LiDAR is mainly used to as existing topological feature vector data. From this vector data LiDAR is used in the form of Digital Elevation Model data.
With the help of LiDAR technologies we can extract terrain features from the LiDAR dataset by using GIS softwares. Mainly earth surface features are represented as vector lines or polylines. All types of vector lines, polygons, and polylines can be converted into a file format for further processing. Sometimes collected data from LiDAR is represented in raster file format or in raster data. For constructing DEM or digital elevation model it is required to convert raster data into digital data. Raster data to vector data conversion includes various Geographical Information System (GIS) processes. The Geographical Information System processes or methods includes filtering, smoothing, edge detection, vectorization, and feature enhancing techniques. We construct or superimposed DEM onto a 2D image.
The demand of Digital Elevation Model is increasing. DEM is used to monitoring coastal erosions, simulation of floods in river basins, and simulation of antennae sites or line of sights calculations for mobile communication network. Some advantages are offers by the LiDAR technologies: elevation and image data is taken at exactly the same time and another facility is that LiDAR DEM may be taken as surface data set to rectify image data.
Sometimes Digital Elevation Model data or DEM is collect using airborne active sensors systems which includes LiDAR or Light Detection And Ranging. LiDAR is an active sensor which emitting a pulse of energy and recording its return at the sensor. LiDAR sensor systems are capable to collect thousands of spatial points on the earth surface in a second and collected points are very much accurate and densely collected points. Points are represents important elevation data. LiDAR systems are working in the clear weather. Most of the LiDAR systems use a near-infrared laser that does not penetrate fog or rain. But longer wavelengths penetrate fog or rain.
The collected elevation data by using LiDAR systems or technologies and ground survey data are cross tabulated with each surface model and the land cover dataset. LiDAR dataset produce accurate information about elevation. With the help of accurate information we are able to construct surface model, elevation model for better representation and analysis of the surface.
Airborne LiDAR