Aerial survey – Automatic data processing
Photogrammetry
Photogrammetry is the art and science of extracting 3D information from photographs. Even they look similar, aerial photographs show the ground plan of the Earth and contain information about the position in which they were photographed. RTK or PPK method ensures high accuracy of photo position, so the error is counted up to 1 centimeter.
With photos recorded from air we create Digital orthophoto (DOF), surface and terrain model (DSM / DTM), 3D object display (3D mesh) and point cloud (Pointcloud). The obtained products are used for various measurements, but they are useful to everyone who cares about the accuracy and credible presentation of an area.
For photogrammetric purposes, we use drones Geoscan 201 Geodesy, Sensefly eBee Plus, DJI Matrice 300 RTK, DJI Matrice 600, Albatros UAV (soon in use). Depending on the project task, we choose the unmanned aircraft with which the task will be completed.
3D
LIDAR
LIDAR or Light Detection and Ranging is a method of collecting data about earth surface, by using ray of lights, that are calculating distance to the earth surface
How does LIDAR work?
How does lidar work? A typical lidar sensor emits pulsed light waves from a laser into the environment. These pulses bounce off surrounding objects and return to the sensor. The sensor uses the time it took for each pulse to return to the sensor to calculate the distance it traveled… In combination with the data obtained from the GPS and IMU systems (position and orientation of the sensor), a cloud of points of different heights (Pointcloud) is obtained. Each point in the point cloud is written in three dimensions and corresponds to a specific position on the Earth’s surface.
To collect lidar images, we use unmanned aerial vehicles DJI Matrice 300 RTK and DJI Matrice 600. Depending on the project task, we choose the unmanned aircraft with which the task will be completed.
Multispectral imaging
Multispectral imaging captures image data within specific wavelength ranges across the electromagnetic spectrum. The wavelengths may be separated by filters or detected with the use of instruments that are sensitive to particular wavelengths, including light from frequencies beyond the visible light range, i.e. infrared and ultra-violet. It can allow extraction of additional information the human eye fails to capture with its visible receptors for red, green and blue. It was originally developed for military target identification and reconnaissance. Early space-based imaging platforms incorporated multispectral imaging technology to map details of the Earth related to coastal boundaries, vegetation, and landforms. Multispectral imaging has also found use in document and painting analysis
Multispectral images are used to study changes in some population, geological changes and transformations, the study of archaeological sites, and are increasingly used to monitor ecological changes. The data collected can be on deforestation, ecosystem degradation, carbon recycling and monitoring of increasingly unstable weather patterns
Also, the use of multispectral images in agriculture has proven to be extremely useful and cost-effective. On multispectral images, farmers can see the condition of their crops. The result of multispectral recording for agriculture is the NDVI (Normalized Difference Vegetation Index), The NDVI is a dimensionless index that describes the difference between visible and near-infrared reflectance of vegetation cover and can be used to estimate the density of green on an area of land which shows the state of the crop based on the light it reflects, ie the wavelengths of the reflected light. Based on the above index, it is possible to conclude which crops are healthy, which have been insufficiently treated with funds, whether they have grown enough…
In general, the result of multispectral imaging is displayed in the form of an index, and in addition to the already mentioned NDVI, there are two other most used indices – NDWI (Normalized Difference Weather Index) and NDSI (Normalized Difference Snow Index). NDWI is used to monitor weather changes, which in everyday life can be seen on meteorological maps, while NDSI is used to determine the presence of snow / ice on the Earth’s surface.
To collect multispectral images we use Sensefly eBee drones with Parrot Sequoia + multispectral sensor.
Thermal imaging
In everyday life, we are surrounded by electromagnetic radiation, although we are often not even aware of it. One part of electromagnetic radiation is recognized by the sense of sight, so it is the visible spectrum of electromagnetic radiation (400-700 nm). Invisible to the human eye, infrared radiation extends above 700 nm up to 1 mm wavelengths of electromagnetic radiation. Although invisible, infrared radiation can be simplified as the heat radiated by any body. Therefore, thermal cameras record infrared radiation, converting it into electrical impulses that correspond to certain temperatures. That is why the result of thermal images is a thermal map that shows an area divided by temperature. The most commonly used display shows warmer bodies with lighter ones, while cooler bodies are shown with darker shades of colors of the visible spectrum
To collect thermal images, we use unmanned aircraft DJI Matrice 300 RTK and DJI Matrice 600. Depending on the project task, we choose the unmanned aircraft with which the task will be performed.
