Digital Elevation Model (DEM) has become a widely used tool for scientists and engineers working with natural forces on Earth. DEM provides an impression of the landscape with elevation values; generally described as a spatially geo-referenced data set that allows computing, model and playing dynamic natural forces interacting with topography and analyzing the impacts. DEMs are mostly generated from remotely sensed data (such as digital aerial photograph, satellite imagery, laser data) and represents complex terrain with adequate resolution. Aerial photographs and satellite imagery have long been used manually by the operators for the extraction of contour lines and DEM data. Computer aided technology such as digital Image Processing has been developed to perform extraction processes automatically or semi-automatically (with operator’s interventions). Automatic Image Processing aims to speed up the batching, computation process exploiting processing speed and intelligence of computers available in the market to reduce the cost.
The DEM used for drawing contour lines or marking the geographical features with smoother and easier slope for computation. The replication of relief and other geographical features can be made after a meticulous and detailed study of the geography and the creation of DEM.
The DEMs can be pre-cast or customized. The DEM engineer should have a pre-estimated of various parameters of quality, lineage, completeness, etc; to predict the appropriate model that will suit the project. The quality of DEM generation depends on the software. Software plays an important role in creating the right characteristics and features. Geographical details should be accurate which are important for subsequent end studies and researches.
Many times, Digital Terrain Model (DTM) and Digital Elevation Model (DEM) are misunderstood by the user for similarity. In effect, both are two different processes. While digital elevation model emphasizes the slopes on a landscape, DTM details the characteristics of the terrains and heights of the landscape. In other words, DTM is the two-dimensional model of the DEM. Concisely; Digital Elevation Models are one of the modern geo-spatial datasets. They are useful for geological and geographical engineering, scientific studies and research. The quality of DEM depends on the software tools used for model generation.
Survey of Bangladesh (SOB) is the national mapping organization (NMO) of Bangladesh. It has the capacity of creating Seamless DEM for the country. As NMO it is responsible for providing topographic map. Now Survey Bangladesh is preparing digital Seamless DEM. At present SOB is preparing DEM data of 20 and 40 meter resolution for the flood plains and hilly areas respectively. Using high resolution Aerial photograph and Satellite imagery and extracting data by latest technology, Survey of Bangladesh is working to create the seamless data by 2020.
In Bangladesh aspect DEM has a great civil and military use for the simulation exercise for the pilots and also war game. Telecommunication sector will be greatly benefited from DEM for planning and positioning signal relay system. DEM data will be of great use for engineering and scientist for watershed modeling, weather modeling, analysis of salinity, modeling for inundation due to tidal surge and many.