What is Photogrammetry?
Remote sensing is the procedure of figuring out information about an object or situation from afar that is, without becoming in direct physical contact with it. A single of the earliest types of remote sensing is the science of photogrammetry, which combines three Greek word roots that mean “light” (photo), “drawing” (gram) and “measurement” (metry). In plain terms, photogrammetry is the potential to figure out measurements via the use of photography.
Two Varieties of Photogrammetry
The two standard classifications of photogrammetry are “aerial” and “close-variety.” As its name clearly states, aerial photogrammetry is accomplished by placing a camera in an airplane and taking photos of the ground, generally in a straight-down manner. The camera’s shutter activates every handful of seconds as the aircraft proceeds in a straight line. In the early days of this approach, film cameras had been utilized. Today, the digital camera is considerably preferred, mostly because tiny additional processing is necessary to manipulate the collected images into anything valuable. Regardless of whether film or digital, every single frame captured by the camera overlaps the next frame. These adjacent pictures are then “stitched collectively,” matching them edge-to-edge in order to come up with a complete picture of the target location.
Close-range photogrammetry involves either a hand-held camera or one mounted on a tripod. As with its aerial cousin, individual pictures overlap and are stitched collectively to create a 3-dimensional image of the object in query. Even though aerial photogrammetry is employed primarily for terrain mapping, close-variety photogrammetry is used to capture images of building facades, autos, or any other physical representation that can be seen from ground level.
A single valuable application for photogrammetry is in the creation of three-dimensional models. This procedure, sometimes known as stereo-photogrammetry, requires the combining of two photographs taken of the exact same object or land function from slightly distinct angles. The old stereopticon, a well-known device back in the late 1800s, utilized a comparable approach to give individuals the feeling they have been seeing anything in 3D. If taken from the air, data captured and processed by means of photogrammetric signifies can aid generate a Digital Elevation Model (DEM), which supplies the viewer with 3D photographic proof of the ground and the objects on it-trees, buildings, organic formations, and so on. Photogrammetry can be combined with other remote sensing techniques, such as LiDAR (Light Detection and Ranging) to create amazingly lifelike photos from the air. These digitized data prove useful to engineers, archaeologists, geologists, mining professionals, city planners, and anyone else needing a highly precise visual map of an area.
The Surveyor and Photogrammetry
Photogrammetry is useful to a surveyor for many reasons. Very first, it allows the collection of visual data more than a significantly bigger region than 1 can effortlessly survey in a affordable quantity of time. Second, the photographs offer a 3D representation of things and landmarks that may possibly have changed more than time, and possibly no longer exist as they after did. Surveyors are oftentimes called upon to show that a distinct object was in a distinct place in respect to yet another object. Whilst a easy photograph may suffice, the capacity to offer this sort of proof in 3D imagery is incredibly strong. Also, photogrammetry and its representation in digital space enables for quite precise measurement. Far far more than a basic photograph, a photogrammetric image is an x-y-z model that has the added benefit of getting fixed to a certain time and location. The digital processing of such imagery adds in GPS measurements to make certain the highest possible accuracy.