Nowadays, digital elevation model (DEM) acts as an inevitable component in the field of remote sensing and GIS. DEM reflects the physical surface of the earth helps to understand the nature of terrain by means of interpreting the landscape using modern techniques and high-resolution satellite images. To understand and analyze the nature of the terrain, DEM is required in many fields in the improvement of developing the product and decision making, mapping purpose, preparing 3D simulations, estimating river channel and creating contour maps to extract the elevation and so on. DEM in various applications will be useful to replicate the overall importance of the availability of worldwide, consistent, high-quality digital elevation models. The present article represents the overall review of DEMs, its generation, development using various techniques derived from topographic maps and high-resolution satellite images over a decade to present. It is useful to understand the nature of topography, address the practical problems and fix them by applying innovative ideas, upcoming high-resolution satellite images and techniques.

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Digital Elevation Models (DEM) of a hilly-valley region are prepared using stereo images of Cartosat-1 and Shuttle Radar Topography Mission (SRTM) images. The procedure of ortho-image generation from Cartosat-1 stereo images and the estimation of ground features from ortho-image are elaborated in the paper. Comparison of DEMs prepared from both images is discussed in terms of the quality of ground features detection, hydrological applications and geometrical calculations. It is found that DEM prepared from Cartosat-1 images are more accurate in the valley region and hence it is better suited for hydrological applications. On the contrary, for hilly region, SRTM images produce better DEM. However, if ground control points and Rational Polynomial Coefficients can be obtained in the hilly region, more accurate DEM can be prepared using Cartosat-1 stereo images.

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