UgCS Pro Controls UAV Most Reliable Over 180 Kilometers
Our task: To completely map the Chemiepark Gendorf (CPG) in southern Germany, an impressive chmical production site, using highly precise PPK drone mapping technology. The requirements have been quite demanding for the flights as well as for the expected results. The resolution (GSD) as well as the absolute accuracy shouldn’t exceed 20 millimetres in X, Y and Z. Based on our technology and know how, we were expecting to get this done, even without using any GCPs for georeferencing. However, in terms of warranties we could not go beyond our 30 mm (RMSE) accuracy promise. Additionally we have been asked to map all asphalt areas and roads in a second part of the project with significant higher resolution. The time frame, to conduct all flights in the month of March, resulted in a quite ambitious and demanding plan: The flights had to be operated in adequate weather conditions, reasonable light conditions, dry roads and roofs and most important due to safety and data protection requirements – only on weekends. The overall project timeline was additionally tight, since the first results like dense point cloud, DEM and orthomosaic were expected to be on the table just about three weeks after the earliest possible flight window. And at that time we could even get some snow, still… Unfortunately the first Sunday in March was quite rainy and even during the second weekend, only Sunday was “flightable”.
The mapping area, slightly over two square kilometres in size (net) has a lot to offer: A almost 200 m high stack, buildings and processing equipment higher than the flight altitude, or safety zones around and above buildings and equipment which are not allowed to be entered e.g. by a drone and last but not least a vertical terrain shift of about 30 meters in the soutrhern part of the park. Regarding take-off and landing areas, we had an additional requirement: Our KLAUPPK system needs a free sight towards GPS and Glonass satellites in order to get good and stable initialization. In a consequence, we only used take off points in the edge area of the site. The need to rely on a GNSS direct georeferencing system was simply due to not having to use hundreds of GCPs and having the experience and proof of accuracy from many past projects. Additionally we did suspect that many existing GCPs would be covered or invisible due to pipe racks, or equipment covering them up.
The schedule was quite ambitious with some uncertainties: Weather conditions, low solar altitude impacting the daily operation’s time, demanding requirements on resolution and accuracy. This all together did require a very thought through, detailed and possibly per-tested mission planning. Our ultimate goal was to be ready for uploading routes once we were entering the site.
The UAV used was a DJI Inspire 2 with a Klau Geomatics modified and calibrated Zenmuse X4s camera (20MP) and a ‘plug and play’ added KLAUPPK GNSS module. To enable a day-long continuous operation, a total of 5 sets of batteries (2 x DJI TB 50, each), three battery chargers and two radio controllers were available. The Samsung “Tab A” tablet, used as screen and HMI/GUI was continuously charged via its USB connection from the radio controller’s battery.
Mission Planning with UgCS Professional
The choice of the mission planning software to use was straight forward, since we already had used UgCS PRO for many missions, even with other UAVs, before, but also since the success of this mission was depending on a very robust terrain following flight altitude. If the terrain follow mode is active, the UAV maintains the height above the ground based on an available DEM, while many other apps available on the market only control the preset flight altitude of he UAV just based on the initial take off point.
We have divided the entire mission into six routes with three to seven flights each, depending on the resulting area size. This enabled us to utilize 6 individual take- off points, meeting regulatory obligations (e.g. VLOS) at any time and generate data chunk sizes, suitable for seamless downstream photogrammetric processing in Agisoft Metashape Pro. The individual routes have been designed with an overlap of one flight line. In order to assure that no critical area will be flown through and the drone will safely fly around the 200 meter high stack, so called custom no fly zones (cNFZ) have been implemented.
In the following we will share the most critical functions UgCS PRO had to offer for this project and how we have them applied:
Using the quite new „Continue Route“ function, the drone resumes the mapping flight at the exact position where the “return to home” function has been activated e.g. to return the drone home or a battery change in the previous turn. This eliminates the pain of taking pictures twice as enforced with many other mission planning tools which force the drone to resume the flight at the last way-point which frequently is the beginning of a long flight line. The efficiency gain is outstanding, accelerating not just the mission itself but also data processing in the office – no need to search for double images and eliminating them.
Area Scan Mode
Despite UgCS has a powerful photogrammetry module with lots of automatic calculations based on the desired resolution (GSD), we have chosen the Area Scan tool for our project. One of the most important reasons, driving this decision was the following: During testing and previous projects it has been observed that the drone flies way beyond the virtual border of the mapping area, defined by the initially created polygon. Even with more complex geometries the base polygon is “ignored” in favor of a most efficient mapping.
Contrary to that in Area Scan Mode the flight lines are mainly oriented to stay within the defined polygon area. This mode requires to define and input the flight altitude above ground (terrain) as well as image spacing (front overlap) and side distance (side overlap) have to be pre-calculated. We have built a simple but comfortable “GSD-calculator”.
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Custom No Fly Zones (cNFZ)
UgCS Pro offers a simple but effective option to define customized no fly zones (cNFZ) in order to exclude automated UAV traffic within an active mission. There are two options available to generate such a cNFZ.
Polygon: Almost like defining a Scan Area any polygon pattern can be defined. Additionally to the base pattern a height can be defined, too. If you skip defining a polygon height the cNFZ will be infinitely high.
Cylinder-Cone: A cNFZ can be defined by assigning a center and a radius and optional by height. If no height will be assigned, the cNFZ’s height is infinite. If a height is defined, it is possible to assign a second radius to this height resulting e.g in a cone or a funnel shaped cNFZ.
In any active mission (Area Scan or Photogrammetry mode) the UAV – as long as the maximum allowable flight altitude, as set in parameters exceeds the cNFZ height – will climb up to the virtual fence height of the cNFZ’s, fly over it and decent back to it’s mission height as soon as it leaves the cNFZ area. In case the cNFZ is higher than the max. flight altitude of the drone, a warning and error message will appear already during the planning process and the mission will not be calculated.
In case the cNFZ is set up in between two individual way-points, the drone’s behavior is identical to the above described. However, if the cNFZ exceeds the drone’s max. flight altitude, UGCS will calculate a route around the cNFZ, without changing the flight altitude.
Both, UgCS desktop software and „UGCS for DJI“ tablet app offer a simulation tool. While the desktop version uses a emulator to test missions and vehicle behaviors the tablet simulator is quite close to reality conditions. In order to use it, the tablet needs to be connected to the drone’s RC as well as it needs to be connected via WiFi with the desktop app. The drone (please remove the props for safety reasons before powering it on) now can fly the mission quite realistically and every movement can be watched on the tablet and computer. Even gimbal actions can be checked on your drone (images are not taken). In addition you can even use the RC’s flight sticks and manually fly your drone on the display.
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