In recent years, Drones (also known as UAS, and UAV) have been widely used in many disciplines, such as geology, geography, ecology, archaeology, and many others. The just passed year of 2016 has even be called the first year in the Drone Age. To assist interested Wash U researchers embracing the Drone Age, we have prepared this guideline of how to use drones to conduct photogrammetric surveys. Since the current version of the guideline is mainly based on our limited experience of using drones, it is far from being comprehensive or authoritative. What it means to is just showing you the basic workflow of a drone-based photogrammetric survey project. So please use this guideline as a starting point and gradually develop strategies that work the best for you.
Before we get into detailed descriptions of the methods, let's first familiarize with some key terms to make sure we are on the same page.
a. Drones
FAA: An unmanned aircraft system (UAS), sometimes called a drone, is an aircraft without a human pilot onboard – instead, the UAS is controlled from an operator on the ground.
b. Photogrammetry
Photogrammetry is a technique used in surveying to measure the three dimensional coordinates with the help of photography. The term “photogrammetry” is composed of the words “photo” and “meter” meaning measurements from photographs. The output of photogrammetry is typically a map, a drawing or a 3D model of some real-world object or land mass.
Fundamental Principle: Triangulation is the fundamental principle used by photogrammetry. In this technique, we take photographs from atleast two different locations. The purpose of taking pictures from more than 2 points is to create what engineers call “lines of sight.” Once these lines of sight are prepared, we join them to locate a point where they meet and thus calculate the coordinates of the desired point. ----civil engineering portal
c. Drone-based photogrammetric survey (UAV photogrammetry)
Drone-based photogrammetric survey is an aerial survey method that combines drones with aerial photogrammetry. It involves mounting a camera, usually pointed vertically towards the ground, on a drone platform. The final products include:
DEM / DTM / DSM (surface models)
Orthophoto’s (geospatially corrected aerial images)
3D Building Models
Contour Maps
Planemetric features (road edges, heights, signs, building footprints, etc)
Main advantages
The benefits of using UAVs for photogrammetric surveying are that their speed, position, and stabilisation can be controlled extremely accurately, so sequential, blur-free aerial photographs of a site can easily be taken, which can then be used to create 3D point clouds, digital terrain models, contour maps, or be merged into a 2D or 3D orthomosaic image.
Moreover, due to the low cost involved, multiple potential archaeological sites can be scouted, rather than focussing all of your efforts on a single location, and the ability to quickly take interchangeable low-altitude aerial shots from vertical, horizontal, and oblique angles allows for a high degree of precision and flexibility which simply cannot be achieved by traditional means alone, or by terrestrial surveying.
While technologies such as Lidar can reveal much about the topographical features of a site, they cannot penetrate the soil. Drones can be fitted with various cameras such as thermal infrared cameras, which can reveal the presence of subsurface stone structures due to the differing heat signatures of the soil and stone and as such, reduce the need for preliminary investigative excavations.
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Fields of application
Forestry Management and Planning
Flood Modelling
Pollution Modelling
Mapping and Cartography
Urban Planning
Coastline Management
Transport Planning
Oil and Gas Exploration
Quarries and Minerals (Volumetrics and Exploration)
Archaeology
Cellular Network Planning