Unmanned Aerial System (UAS) Scenario Evaluations

This is one of the many forms of an unmanned aerial system. Multicopters (pictured) can be used in situations that require precision in tight spaces. Vertical takeoffs and landings make multicopters one of the most versatile UAS.

Introduction: With the fast paced development of geospatial technology, applications of the new information systems are growing exponentially. The perfection of remote sensors in functionality and size has expanded the range of what vehicles or systems can be fitted to carry and capture information. Tasks that were once only capable on foot or in person are now able to be done via satellite or unmanned aerial systems (UAS). Unmanned systems are both used by the military as well as by civilian contractors and are capable of unpiloted flight. Several types of UAS exist and each can provide different sets of benefits to evaluate tasks quicker and, in most cases, provide a less costly alternative.   

Fixed-wing unmanned aerial vehicles require a strip to takeoff and land. The ability to glide and carry large payloads offers the consultant a wide range of options for sensors and other hardware to complete a survey.  

Fixed-Wing Craft: Fixed wing vehicles are the most familiar or “search image” for what people think a UAV or UAS is. These crafts have two fixed wings as the name suggest that allow gliding and stable flight with greater payloads and longer flight times as compared to copters. The wings allow the craft to glide in an event of power failure which copters are not able to do providing a better peace of mind for the pilot; however, the fixed wings don’t allow the craft the ability to hover in a single spot or allow for a vertical takeoff. Like any standard gliders or airplane, a fixed wing craft requires a runway for takeoff and landing. Fixed wing crafts are available in gasoline or electric power. The gas powered flights can last about 10 hours and electric about 45 minutes to an hour depending on the payload.

Helicopters, with the ability to hover, provide the user to focus on a specific area of interest or reach areas quickly and precisely. Since they takeoff and land vertically, a helicopter can be launched in a confined space that a fixed wing craft would be unable to. 

Helicopter: Helicopters are operated by a single lifting motor with two or more blades. The lifting motor allows for a vertical takeoff and landing allowing the system to be launched in a limited area. The blades are able to be pitched to compensate for winds and directional change. For an operator, it is safer for the motor and radio equipment on board to have separate power sources. This not only helps to return the craft but also increases safety when working or performing maintenance on the system. Copters are fast and efficient but can create vibrations that can reduce quality of video or information. The location and mounting systems can limit the vibration allowing for accurate data. Helicopters are powered by either gasoline or electricity. Gas powered systems have a flight time of 4 to 5 hours while electric powered systems are limited to 20 to 90 minutes. Flight times are limited by payload as well as configuration of the system.

Multicopters provide yet an even more stable and controlled response in a UAS. With multiple arms, balance in winds and flight allow a multicopter to be the most versatile and reliable UAS. 

Multicopter: Multicopters utilize several rotating blades to achieve lift and control. Each blade set is controlled by a separate motor allowing the system to balance, provide lift, and have precise directional controls when hovering. The multiple arms allow for a higher degree of safety when performing maintenance tasks by operating at smaller radii than a helicopter. The multiple blades or arms of the system also require more powerful computer processors without which the craft can’t fly; however, the varying designs for multicopters offer a degree of flexibility unavailable to helicopters or fixed wing crafts in the location of sensors and other operating equipment. This variation also enables the multicopter to be more stable in high wind conditions compared to other aerial vehicles but with more arms on the multicopter, the shorter the flight time. The stability is great for beginner operators as well as those who need the stability to focus on an area in great detail.  

What do you need: There are several pieces of equipment that are required for every UAS, some more obvious than others. You will need to consider what you are trying to survey then determine the type of vehicle, autopilot, planning software, and payload the vehicle will be carrying. The vehicle, fixed wing, helicopter, or multicopter will determine which of the systems will be needed as well as determine the size of the payload. APM 2.6 autopilot hardware provides processors, gyroscopes, accelerometers, pressure sensors, and a GPS to any vehicle (ArduPlane for fixed wing ArduCopter for rotary wing) with a reasonable cost at $179.00. The ArduPlane or Copter software allows the user to pre-plan a flight pattern into the system allowing the pilot to monitor the system rather than solely focusing on flying the vehicle. The planning software also ensures that the necessary overlaps for images as well as insuring precise points of interest are located quickly and accurately. In the event of the vehicle flying out of the range of the manual controls or equipment failure, the software provides a failsafe by automatically returning the aircraft to the point of take off. The payload will vary with vehicle and duration of the flight. Longer durations of flight will require smaller payloads since more operating power will be needed. High definition cameras, thermal scanners, infrared scanners, or LiDAR are just a few possible sensors that are capable of being installed on a UAS. Again, which sensors are necessary will depend solely on what the subject of the survey will be.     

Scenarios: There are many real world applications of UAS. The following list provides several examples of those scenarios and provides possible solutions on which UAS and technology would be most helpful to meet the goals of the individual client.

The desert tortoise is a threatened species in the United States. Threatened species are not in danger of extinction but population sizes are small and if not monitored closely may become endangered. With this threatened title, the tortoise habitat is protected under the Endangered Species Act. 

Scenario 1: A military testing range is having problems engaging in conducting its training exercises due to the presence of desert tortoises. They currently spend millions of dollars doing ground based surveys to find their burrows. They want to know if you, as the geographer can find a better solution with UAS.

        Questions: What do we know about the tortoises? What can we use to locate burrows? How large is the testing range? How often are exercises conducted? What is the budget?

        Background: Desert tortoises are herbivores that feed on grasses, wildflowers, and cactus pads that are available in the deserts. Tortoises live in burrows to escape the extreme heat of the environment and lay dormant from November to February. 97% of tortoise burrows are associated with shrub vegetation allowing the tortoise to eat in the spring. The soil needed to create the burrows is also particular to the tortoise. Moisture and texture has to be perfect that it crumbles during digging but is firm not to collapse. Commonly burrows are found in sandy loam soils with gravel and clay not areas with a lot of sand.

        Solutions: With military operations possessing fixed wing aircraft, a possible solution to locate the burrows could be outfitting a UAV or manned aircraft with a few new sensors. The fixed wing UAS has a stable flight with the capability of long flight durations. With the burrows being typically located near dense vegetation, a near infrared scanner would be able to locate those vegetated areas. Next, the suitable soil could be located using variations in moisture content measurable by a short-wave infrared sensor. Areas with higher moisture content will display weaker in the sensor readings due to the absorbance by the water rather than reflectance by the dry sands. Once paired with the vegetation and suitable soil locations, a thermal imager may be capable of locating the entrances of the burrows. The cooler soil would stand out from the stark hot surface of the surrounding areas. An overlay analysis could be performed and those areas that are most suitable for burrows can be mapped providing a guide for later surveys. The use of these sensors can’t be 100% accurate so foot inspections may still be needed but much less intensive than without the UAS.

For years, utility companies have hired helicopters to fly along power lines to perform inspections. This is a very dangerous and therefore costly process that can be reduced with the help of a UAS. 

Scenario 2: A power line company spends lots of money on a helicopter company monitoring and fixing problems on their line. One of the biggest costs is the helicopter having to fly up to these things just to see if there is a problem with the tower. Another issue is the cost of just figuring how to get to the things from the closest airport.

        Questions: How often do problems occur along the power lines?  How much does it cost to get the helicopter out to inspect the line?  Are the lines accessible to ground crews to get close enough quickly enough?  What type of area are the power lines in, populated or rural?

        Solutions: A multicopter would be a good option to perform this task.  A ground crew with the multicopter would get close enough to the power lines that they wish to examine in order to use a multicopter. The UAV multicopter should be installed with a high quality camera and should be able to operate at a relatively low noise level to prevent disturbing wildlife or cattle that may be in the area.  It would also be advantageous to have some way for the copter to detect changes in the electrical field around it so it could detect anything that may be wrong with the power lines. This multicopter has high payload capacity (3kg) for high definition imagery, rotors covered for safety when flying near power lines, is equipped with excellent crash/accident avoidance technology such as its “coming home” function, very stable when holding position for excellent imagery, and comes with some of the best pre-mission programming.  It will cost around $30,000 per multicopter but this will pay off in the long run when considering the company cost paying a helicopter to go out to check the power lines repeatedly.  It’s not an inexpensive start up cost but will pay off in the end, as this is a very reliable model. It may also be a good idea to have a UAV helicopter along as well. If a power line needs to be looked at rapidly due to an emergency, the helicopter can be launched from further away due to its longer range.  The same considerations regarding weight, noise level, image quality, and maneuverability would need to be taken into consideration for the helicopter as for the multicopter.  

Pineapples are a short bush like plant that is commonly grown in tropical areas. As the fruit matures, it rises out of the center of the plant and gradually begins to turn a bright yellow. 

Scenario 3: A pineapple plantation has about 8000 acres, and they want you to give them an idea of where they have vegetation that is not healthy, as well as help them out with when might be a good time to harvest.

        Questions: What type of area is the pineapple plantation in? What is currently being done to assess these problems?

        Background: Pineapple plants are read to harvest when they are in the late stages of their development.  This means that they have over 1/3 of their peel as a yellow color but they haven’t lost all of their green yet. Near infrared reflection has been tested to see whether or not it can be used to detect ripeness of a plant, as the plant gets riper, the NIR tends to decrease.  This fact combined with the fact that when pineapples are ready to harvest they shouldn’t be ripe yet and shouldn’t be harvested until their skin is 1/3 yellow and 2/3 green can help determine the best time to harvest the pineapple.  Using a multi-spectral approach with both visible wavelengths to try and determine color and NIR wavelengths to determine health and whether the plant is ready to harvest.

        Solutions: A gas powered UAV helicopter equipped with a near infrared (NIR) camera sensor which will detect higher reflectance of healthy vegetation will help locate the ripened fruit.  This UAS would require pre-mission software that would allow it to track and cover the whole field recording data spatially.  Ideally this would be done during the day when there is the highest amount of NIR reflection. A gas helicopter would provide the focus and maneuverability needed to survey the pineapples. The size of the field would limit a multicopter to short flights where the helicopter could fly for longer durations. The NIR camera has a high range of reflectance allowing the distinction of healthy and unhealthy vegetation. Healthy vegetation reflects significantly more NIR waves allowing the healthy plants to be displayed more prominently than the unhealthy vegetation.

The Niger River delta is one of the largest in the world and is also one of the most polluted. Stretching thousands of miles across western Africa, the river passes through several oil rich lands increasing the pollution risk. 

Scenario 4: An oil pipeline running through the Niger River delta is showing some signs of leaking. This is impacting both agriculture and loss of revenue to the company.

        Questions: What is the range of possible leaking points in the pipe? Will there be any restricted areas to avoid? Are there fire risks? Will the UAS be flying over populated areas? What time of year will surveying occur?

        Solutions: The survey area is large requiring a UAS with a large antenna which will allow for a longer flight range from the computer base. The best type of craft for this mission would be a gas powered fixed-wing craft. This would allow the payload capacity needed and provide the stability required. The main sensor required on the plane would be a small thermal imaging camera to record the thermal readings of the ground along the pipeline, just after sunset, from which one can deduce the thermal heat capacity of the ground. If there is a leak, the oil will produce a thermal reading that differs from the heat capacity of the surrounding materials.

Surface mines are those at which layers of earth are scraped and dugout then processed to separate the precious metals or stones. The earth is removed until the ore is depleted and operation is no longer profitable by the company. This Russian diamond mine is over 600 feet deep. 

Scenario 5: A mining company wants to get a better idea of the volume they remove each week. They don’t have the money for LiDAR, but want to engage in 3D analysis (Hint: look up point cloud)

        Questions: What is the project budget? How expansive is the mining operation? Is this an open pit mine?

        Solutions: Aerial photos need to be taken of the mine area with a high percent of overlap (>60%). Use of a multicopter or helicopter would provide the control and stability to capture quality images, however if the budget is constrained, the use of a kite may also serve well to photograph the area. From online servers such as Photosynth, the photographs can be uploaded to create a point cloud of the area. A point cloud is a set or fabric of dense points that hold elevation as well as coordinate information. From the point cloud, a digital surface model can be created and be capable of calculating changes in volume along that surface. Like the servers that create the point clouds, there are open source products such as Meshlab that allow the surface calculations to be done. If the budget allows, ArcMap with the 3D analyst extension will also allow the creation of the surface model from the point cloud. With use of the SurfaceVolume tool, ArcMap can also calculate the difference in the surface from a set reference plane allowing the changes in volume to be tracked over time.   

Information complied by: Jake Burandt, Tim Condon, and Brielle Cummings