Drones are transforming the way we see the world around us. Terrain modeling, for example, give an overview of landscapes, and the words often used when describing these landscapes are: “fascinating, breath-taking, overwhelmingly beautiful, spectacular,” etc. In fact, words often fail when trying to describe what sometimes seems indescribable.
What makes such beautiful landscapes so spectacular is a combination of the skills and talents of artists who invested all their knowledge, passion and time into drone technology.
Drones are transforming the way we see the world around us. They also impact how we think about the world, which affects how we interact with the world. One of the dramatic ways that has affected both terrain modeling and drones is how we see and think about the world, is the ability to create highly accurate 3D models of surfaces and objects using various sensor arrays.
This newer technology has not only enabled us to see and appreciate the beauty, but has also given us the ability to see the world as it is, that is, the incredible detailed photography that 3D models produce show us what the world really looks like, thus a more realistic look at the world. This enables us to not only appreciate the beauty, but also helps us to be able to address the parts of the world that need our attention.
Drone surveys refer to an unmanned aerial vehicle (UAV) capturing serial data with downward-facing sensors, such as RGB or multispectral cameras and LiDAR payloads.
During the drone survey with an RGB camera, the ground is photographed numerous times from different angles, and each image is tagged with coordinates. Photogrammetry combines images that contain the same point on the ground from multiple vantage points which results in detailed 2D and 3D maps.
Photogrammetry software can then create geo-referenced orthomosaics, elevation models or 3D models of the project area, from this data, and these maps can also be used to extract information, such as highly-accurate distances or volumetric measurements.
Unlike traditional aircraft or satellite imagery, drones can fly at much lower altitudes, which makes this generation of high-resolution and high-accuracy data, much faster, less costly, and independent of atmospheric conditions, such as cloud cover.
Digital elevation models can be extremely useful in that they can model surfaces for a wide range of applications, such as infrastructure issues, construction site planning, etc. Digital terrain models (DTM), digital surface models (DSM), or digital elevation models provide an extremely specific and accurate 3D representation of a surface.
The accuracy of any map will be determined by the hardware itself and by the operation of the drone. The hardware is made up of the GPS system being used and the LiDAR or resolution and shutter-speed of the camera. The operation of the drone entails the specifics of the operation such as the altitude or speed of the flight.
One of the major advantages of drones is that they are able to get much closer than conventional aircraft and therefore provide a significantly higher resolution, which results in a more accurate ground sampling distance (GSD). This is critical for constructing a photo realistic model in the absence of LiDAR.
During such operations, the UAV takes hundreds of photos at the correct intervals and overlap ratios in order to “stitch” them together into a single large photo (e.g. an orthomosaic). The same algorithms that create the orthomosaic can also create three- dimensional digital surfaces.
One drone flight produces thousands of measurements, which can be represented in different formats (orthomosaic, point cloud, DTM, DSM, contour lines, etc) and then each pixel of the produced map or point of the 3D model contains 3D geo-data.
Drone surveyors can capture many more topographic data points, and thus more accurate volume measurements, and they can do this in a much safer way than if they had to manually capture the data. Since drones are capturing the data from above, operations on site will not be interrupted, and the short acquisition time enables them to capture a snapshot of a site at a specific point in time.
The following are common places for terrain modeling:
- Volcano craters
- Glacial features
- River banks
- Morphology
- Cliff faces
- Beaches
Present & Future Benefits
Surveying with a drone offers enormous potential to GIS professionals. An aerial surveying or mapping drone can take off and fly almost anywhere. They are not limited by otherwise unreachable areas, unsafe slopes, or harsh terrain unsuitable for traditional measuring equipment. With a drone, it is possible to carry out topographic surveys of muchbetter quality than the measurements collected by traditional methods.
