You’re about to start a drone mission to create an aerial map of an area, or an inspection of an asset for a commercial use case. Time to fly, right? Well before you do, you’ll need to properly plan your drone flight and determine what level of detail and accuracy is required to suit the needs of the project. The processing type (aka digital photogrammetry) that will support those needs should be considered, along with the level of positioning accuracy required. Enter PPK, GPS and RTK geotagging.
One of the key challenges with drone aerial imagery is ensuring that the captured images are accurately georeferenced. This is where geotagging technologies come into play. By adding geographic location data to each image, geotagging technologies such as GPS, RTK, and PPK can significantly enhance the accuracy of drone aerial imagery. In this article we will explore these geotagging technologies.
There are three main technologies that are commonly used for positioning and georeferencing: RTK, GPS, and PPK. While these technologies share some similarities, they also have some key differences that ultimately affect their level of accuracy. Depending on the use case, you may require more or less accuracy;
GPS (Global Positioning System). GPS is a satellite-based positioning system that can provide location information to a drone. It works by using signals from a network of GPS satellites to determine the drone's location. GPS provides good accuracy, typically within a few metres, but this can be affected by factors such as atmospheric conditions and signal obstructions.
PPK (Post-Processed Kinematic). PPK is a technique that uses GPS data collected by the drone during a flight to improve the accuracy of the georeferencing after the flight is completed. PPK works by comparing GPS data to a known base station location to calculate corrections to the GPS data. These corrections can then be used to improve the accuracy of the georeferencing of the captured images. PPK can provide higher accuracy than GPS alone, but not as high as RTK.
RTK (Real-Time Kinematic): RTK geotagging is a technique that uses GPS in combination with a base station to achieve centimetre-level positioning accuracy. The base station transmits correction signals to the drone, which allows the drone to correct for errors in GPS measurements and achieve a more accurate position. RTK is particularly useful for applications that require high-precision positioning, such as surveying and mapping.
GPS, RTK, and PPK are all considered geotagging technologies. Geotagging refers to the process of adding geographic location data to a photo or other digital media. In the context of drone aerial imagery, geotagging involves adding GPS coordinates to each image to enable them to be accurately georeferenced.
GPS provides location information that can be used for geotagging drone imagery. RTK geotagging and PPK can both be used to improve the accuracy of geotagging by providing higher-precision location information. RTK achieves this by using a base station to provide real-time corrections to the GPS signal, while PPK achieves this by post-processing the GPS data after the flight is completed.
Real-Time Kinematic (RTK) is a satellite navigation technique that enables drones to achieve centimetre-level accuracy in their positioning. By using RTK, an RTK drone can determine its exact location with a high level of precision, which in turn improves the accuracy of the aerial imagery it captures.
RTK works by using a fixed base station on the ground, which is equipped with a GPS receiver and a known position. The drone, which is also equipped with a GPS receiver, receives signals from the base station and uses them to calculate its own position. Because the signals from the base station are more accurate and stable than the signals from GPS satellites alone, the drone can determine its position much more precisely.
This precise positioning enables the drone to capture aerial imagery with a high degree of accuracy. For example, when capturing images for mapping or surveying purposes, RTK can help ensure that the images are accurately aligned and georeferenced, allowing for more accurate measurements and analysis.
PPK (Post-Processed Kinematic) geotagging is a method for determining the precise location of an aerial mapping drone during flight. It uses GNSS (Global Navigation Satellite System) signals from multiple satellites and an on-board GNSS receiver to determine the drone's position in real-time. The data from the flight is then processed after the flight using base station data to achieve a high level of accuracy.
PPK geotagging increases the accuracy of the drone's aerial images and mapping data by combining GNSS signals with the data from the on-board GNSS receiver to accurately determine the location of each photo. This reduces the need for ground control points (GCPs) as the geotagging technique provides precise location information for each image. This results in faster, more efficient mapping and a higher level of accuracy compared to traditional geotagging methods. PPK geotagging is commonly used in applications such as surveying, mining, power/utilities, and construction where accuracy is critical.
GPS, or Global Positioning System, is a satellite-based navigation system that can provide accurate positioning information for drones. By using GPS, a drone can determine its location, altitude, and orientation, which can improve the accuracy of the aerial imagery it captures.
When a drone captures aerial imagery, it typically embeds the GPS coordinates of each image as metadata. This allows the images to be accurately georeferenced, which means that their geographic location can be precisely determined. Georeferenced images can then be used for a variety of purposes, such as mapping, surveying, and inspection, and it’s the GPS metadata within each image that enables platforms like Birdi to visualise the precise capture location in our Map View.
GPS can also help drones to maintain their position and altitude while capturing imagery. This is especially important in areas where there may be obstacles or difficult terrain that could cause the drone to drift or lose its position. By using GPS, the drone can maintain a stable position, allowing for more accurate and consistent imagery.
In addition, GPS can be used in combination with other sensors, such as accelerometers and gyroscopes, to improve the overall accuracy of the drone's positioning and orientation. This can help to ensure that the drone captures high-quality imagery that is aligned and properly georeferenced.
Now that you're all clued up on PPK, GPS and RTK geotagging in drone aerial imagery, you can go ahead and choose the best approach for your project. Happy flying!