Aerial Triangulation (AT) is an integral part prior to producing any photogrammetric products from Stereo images. It is a mathematical process to determine the position and orientation parameters (Exterior orientation) of the photographs at the time of exposure that is eventually used for orthophoto generation, at mapping and height model generation.AT is a critical step related to the project's quality, and can be represented as the heart of all photogrammetric processes as the quality of the exterior orientation parameters and the scale of the photographs are the determining factors in the quality of the mapping products.
An orthophoto is a photograph that is geometrically corrected or orthorectified. It can be considered as an image representation of a map where the scale is uniform. Orthophoto can be used to measure true distances, unlike an uncorrected aerial photograph, that represent the earth's surface, as it has been adjusted for topographic relief, lens distortion, camera tilt etc.Orthophoto is often a mosaic of a series of orthophotos that covers a small or large area of land where all individual orthophotos are feathered / blended together following some seam lines. These seam lines can be generated either automatically or manually.Regardless of how they are created, the seam lines defines where in the overlapping zone between two images the actual division will take place. As a result, automatically generated seam lines need to be checked whether they are crossing a building, structure etc. to ensure a seamless mosaic.
The Vector Map (VMAP), also called Vector Smart Map, is a vector-based collection of Geographic information system (GIS) data about Earth at various levels of detail. Level 0 (low resolution) coverage is global and entirely in the public domain. Level 1 (global coverage at medium resolution) is only partly in the public domain.Vector maps are the representation of topographic mapping features consisting of point, line and area. It consists of preparing vector or topographic data from stereo aerial/RS images based on specification that usually used as an input for both public and private administrative tasks and construction projects right from the planning phase until the project terminates. Specification for mapping of topographic and thematic features depends on the clients requirements that vary with individual countries and projects.Rester to victor convertion from streoploting using ArcGIS and DAT/EM System .
There is an increasing need for the 3D models of urban areas for applications like town planning, microclimate analysis or transmitter placement in telecommunication. 3D city model plays a very prominent role now a day's that is well suited for presenting even very complex problems in an easily accessible manner. This realistic visualization provides an easy and comprehensive overview of major construction projects, urban design, development and other high level urban investments.3D-visualisation concept for city environment is a professional basis for planning, simulation, renovation and development. It gives a provision to the decision makers to make a realistic assessment of all consequences of a decision.Google Earth and Google’s recent acquisition of SketchUp has sparked tremendous interest in 3D city modeling. Microsoft’s recent acquisition of the 3D visualization company GeoTango suggests that Microsoft's Virtual Earth, too, will soon be providing 3D capabilities. 3D in other Web mapping services is likely to follow.DAT/EM Systems International is an Alaska-based company that has been developing photogrammetric software since 1987. As a leading developer of photogrammetric hardware and software products and services, DAT/EM specializes in 3D feature collection software with its digital stereoplotter, SUMMIT EVOLUTION, and its point cloud viewing and editing product, LANDSCAPE
Light Detection and Ranging or LiDAR is a mapping method in which the distance to the ground is measured from an airborne platform by means of a laser scanner. This scanning process generates a considerable amount of so-called point cloud consisting of points with position (x, y and z) and altitude information. Typically two models are composed from the points, DTM (Digital Terrain Model) and DSM (Digital Surface Model). These point clouds can be filtered and classified to generate very accurate DTM (Digital Terrain Model), DSM (Digital Surface Model) and for a variety of GIS-applications like flood plane modeling, analyzing forests, determining the height of power lines, hydrological modeling and for 3D city models.In order for the laser scanning data to be useful, for example to generate terrain models, every single point in the point cloud must be classified to categorise the points that hit the terrain. There is a number of softwares that classify the points automatically. But to obtain an acceptable quality manual checking is almost unavoidable.LiDAR data editing from DAT/EM system
Height models often refer to digital terrain models (DTM), digital surface models (DSM) and digital elevation models (DEM). It is a representation of the topographic surface and is usually presented as a raster or as a triangular irregular network.Height models are largely used in many geographic and spatial analyses for the purpose of modeling the land, water, wind, noise and pollution. It is also used for the production of orthophotos, making 3D city models and for the telecom industries to model signal propagation.height models produces from the following data sources: