Today, mapping is not just handwork of artists; time has revolutionized the technology, bringing about innovation that repeats to an unforeseen future. People no longer take pain drawing irregular curves and corners in maps using their pencils and sketches, rather they convert the digital images of geography into information tools and maps. In this scenario, discussing on reliable mapping technology like Photogrammetry is promising and incisive.
Photogrammetry, in general, is the latest available technology, which helps to shape, orient, size and position objects from numerous pictures taken at different angles. It is widely used in Geospatial arena to produce topographic maps, which includes both orthophoto maps and line maps. These maps help to determine the accurate position, height, width, orientation, and shape of geographical features. Pictures generated after photogrammetry are photochemical images or photoelectric images depending upon the photographic methods followed in the process. The output of photogrammetric analysis can be numbers, drawings, geometric models and images. Photogrammetry is used for different purposes, such as topographic mapping, architecture, engineering, manufacturing, quality control, investigation, and geology. This technique is employed to combine live action with computer generated imagery in movie post-production.
Photogrammetry process includes two key processes- Orthorectification and Remote Sensing. Orthorectification is the technology employed to transform the central projection of the photograph into an orthogonal view of the ground, thereby removing the distorting effects of tilt and terrain relief. Remote Sensing is used to acquire geospatial information about earth's surface using the reflective and refractive properties of electromagnetic radiations (EMR). In a way, both are distinctive parts of photogrammetry offering the technology for substantiating map information.
The by-product of orthorectification process is orthoimage or orthophotos. Digital satellite images and aerial photographs play a vital role in general mapping, as well as GIS data acquisition and visualization. The orthorectification process provides you a solid visual effect and a basis for gathering spatial information. The output generated would then enable you to do functions like making direct and accurate measurements of distances, angles, positions, and areas. Through remote sensing spectral, spatial, and temporal information about material objects, area, or phenomenon is acquired. In other words, remote sensing enables space information transfer without direct physical contact with the objects, or area, or phenomenon under investigation.
While these two technologies are nodal in photogrammetric services, there has been continuous improvement in the technologies used for mapping. The arrival of high speed desktop computers has made remarkable changes in the photogrammetric processes over the years. However, the basic principles have remained the same until this day. Today, a graphics program allows the operator to digitize the features and save the vectors and points to a digital file. The latest technologies used for photogrammetry services include Aerial triangulation, Digital Elevation Model (DEM)/ Digital Terrain Model (DTM) generation, Stereo compilation, Topographic and planimetric feature extraction, Orthophoto production, Color balancing, Mosaicing and tile generation, Pan Sharpening, Contour Generation, and LiDAR data processing.
Concisely, Photogrammetry helps to collate accurate information to topographic maps and thereby provide reliable resources for geographical studies. With the introduction of new-age fast processing systems and technological advancements, we can expect simplification of photogrammetric services and enhancement of Geospatial information System (GIS).