Mapping accuracy

Everyone knows about maps and their use Everyone is familiar with Google Maps Hence most of the people know about GIS and its application

Updated At : 06:11 AM Feb 22, 2017 IST

Preetinder Kaur

Everyone knows about maps and their use. Everyone is familiar with Google Maps. Hence most of the people know about GIS and its application. But very few people have known and understood what is the science behind photogrammetry and what exactly is done that makes it different from a normal map making/digitization.

Photogrammetry is the science of making measurements from photographs. The output of photogrammetry is typically a map, drawing, measurement, or a 3D model of some real-world object or scene. Many of the maps we use today are created with photogrammetry and photographs taken from aircraft.

Photogrammetrists examine pictures taken with remote viewing equipment (such as satellites or mounted cameras) in order to create specialised maps of different geographical regions. Professionals carefully analyse each picture to determine the measurements and locations of each identifiable object, and then they input that data into computerised map-making programmes.

If you wish to pursue a degree in photogrammetry, you will need to obtain a bachelor's or master's degree in Geomatics. A degree in Geomatics may be the best option, as it combines cartography (mapping technology) with geography (land surveying).

You may learn about GIS, GPS, and LIDAR systems, computer programming, engineering, mathematics, and map-making. Additionally, land planning, geodesy (astronomical and mathematical study of Earth-shaped spheres), remote sensing, photogrammetry, and mapping legal concerns may also be studied along with it.

Types

Photogrammetry can be classified a number of ways but one standard method is to split the field based on camera location during photography. On this basis we have Aerial Photogrammetry, and Close-Range Photogrammetry.

In Aerial Photogrammetry the camera is mounted in an aircraft and is usually pointed vertically towards the ground. Multiple overlapping photos of the ground are taken as the aircraft flies along a flight path. These photos are processed in a stereo-plotter (an instrument that lets an operator see two photos at once in a stereo view). These photos are also used in automated processing for Digital Elevation Model (DEM) creation.

In Close-range Photogrammetry the camera is close to the subject and is typically hand-held or on a tripod (but can be on a vehicle too). Usually this type of photogrammetry is non-topographic that is, the output is not topographic products like terrain models or topographic maps, but instead drawings, 3D models, measurements and point clouds. Everyday cameras are used to model and measure buildings, engineering structures, forensic and accident scenes, mines, earth-works, stock-piles, archaeological artifacts, film sets, etc. This type of photogrammetry (CRP for short) is also sometimes called Image-Based Modeling.

Getting in

A bachelor's degree in surveying is generally required. However, qualifications in geography, geographic information systems, remote sensing, land surveying, computer science, statistics or a related field are beneficial.

Branches include web mapping, cartography, geodesy, disaster management, global navigation satellite systems, remote sensing and geographic information systems.

Currently the main focus of studying Photogrammetry includes terrain height extraction using photogrammetric techniques and LiDAR, close range photogrammetry, advanced image classification and processing, automatic feature extraction, GPS, and hyperspectral and microwave image analysis.