Drones are getting popular in engineering applications. Is their popularity worth a shot in aerial surveying and mapping?
In aerial surveying, traditional methods of obtaining actionable information require a huge number of surveying workforce. The process is time-consuming and often difficult to manage. Drones, on the other hand, offer huge content without risking the health and safety of the workforce.
UAVs are changing the face of professional surveying. They offer a huge help by obtaining accurate, up-to-date data and a number of solutions which are used differently as per the organization’s need. Some of the popular ones are:
Orthomosaic
Orthomosaic is made from two words Ortho (meaning perpendicular) and Mosaic (meaning small pieces joined together to make a big piece). An orthophoto, or orthomosaic is a large image of an area which can be used to measure actual distances between any two given points on the image. A normal photograph, as taken from above is not uniform in terms of scale (It means that the ratio of the distance between two points on a photo to the actual distance between the same two points on the ground is not equal). However, an orthomosaic is such that the scale of the image to the actual ground is uniform, thus, representing the Earth’s actual surface. To view orthomosaic online, one can refer to softwares such as Felix, Pix4D, etc.
In simple words, an orthomosaic is an accurate representation of the Earth’s surface from a top view in 2D.
Digital Elevation Model
Elevation means height. In simplest terms, it can be referred as Digital Height Model. Thus, a digital elevation model (DEM) is a representation of a terrain’s surface only in terms of its height. DEMs are the superset of digital surface models (DSM) and digital terrain models (DTM).
Digital Surface Model (DSM): As the name suggests, a digital surface model is a digital representation of the Earth’s surface (in terms of height). In other words, DSM provides the height of all the points on Earth as seen from above such as buildings, trees etc. It is obtained directly from any standard photogrammetric software.
Digital Terrain Model (DTM): It is similar to a digital surface model; except it represents only the bare surface of the earth, without including any height information about the structures above ground such as buildings, trees, etc. It is a bare earth model. A DTM is obtained from further processing of a DSM is used to generate a contour of the given area.
Point Cloud
Imagine the real-world in form of points! That’s what a point cloud is — a 3D representation of the real-world in form of points. In other words, it is a collection of a large number of points/pixels (>1 crore) where each point has X, Y and Z location in a given 3D coordinate system, and also a corresponding R, G, B colour value, such that all the points when combined according to their position in the coordinate system, it looks a digital copy of the real world.
Unlike Orthomosaic, where we can do only 2D measurement (distance/length), Point Cloud gives us the freedom of measuring in 3D and hence enabling us to find out height difference between two points, volume estimation of a specified region, elevation profile of a section etc. The compatible online software for point cloud are Felix, Pix4D etc.
3D Mesh
A 3D Mesh is the most accurate representation of the real-world in every form. Unlike point cloud, which is a discrete set of points, a 3D Mesh is continuous similar to the real world. It also gives us the freedom of measuring in 3-dimension (3D), and hence, enabling us to find out height difference between two points, volume estimation of a specified region, elevation profile of a section etc.
UAVs have inbuilt obstacle avoidance capabilities which enable them to closely monitor and collect comprehensive data. Several industries are already using aerial drones to inspect assets. While others are just starting.
