Field Activity 3: UAV Systems Research and Advising

Introduction:

This week's activity is less of a "field activity" and more of a research project.  The class was given five scenarios (which will be laid out later in this report) and required to find a solution to each scenario using and involving UAV systems.  These problems are inherently ambiguous as the class was required to ask questions and use critical thinking to find solutions.  This activity requires knowledge that goes above and beyond that which is typically required for classwork so coming up with solutions required intricate research into each situation and into the various UAV systems themselves.

UAV Overview:

An Unmanned Aerial Vehicle (UAV) or Unmanned Aerial System (UAS) is an aircraft that has the capability of autonomous flight, without a pilot in control. Amateur UAVs are non-military and non-commercial. They typically fly under “recreational” exceptions to FAA regulations on UAVs, so long as the pilots/programmers keep them within tight limits on altitude and distance. Usually the UAV is controlled manually by Radio Control (RC) at take-off and landing, and switched into GPS-guided autonomous mode only at a safe altitude. UAVs can typically be piloted using an autopilot. This software can either come with the UAV when purchased or can be purchased seperatedly. An example of this software is APM 2.6 autopilot which retails for around $200. Mission planning software is also an essential function of successful use of a UAS. This is a software that allows a ground station to keep constant surveillance of a UAS while it is in flight. Depending on the software, full flight missions can be pre-programmed into the UAS using the mission planner. Data can be analyzed in real time using a graphical interface, and the UAS may be piloted using the ground station in place of the typical remote control. Two examples of this software that are popular in today's market are APM:Plane for fixed-wing aircraft and APM:Copter for rotary-wing aircraft. This software may come with the UAV when purchased.  

Three common types of UAVs include fixed-wing aircraft, helicopters, and multi-arm copters (multicopters).

Fixed-Wing Aircraft:
When it comes to UASs, fixed wing aircraft are essentially small, unmanned planes. They are capable of long flight times depending whether they are gas powered (typically 10 hours) or electric powered (typically up to an hour). Fixed-wing UAVs are more forgiving than rotary craft in the event of mechanical failure and/or pilot error due to their natural ability to glide without power and can carry larger payloads than a typical rotary craft for longer distances on less power. However, a fixed-wing UAV cannot hover in one spot as rotary craft can, and due to this they cannot provide the same level of precision imagery as rotary craft. Fixed-wing craft also require a runway to take off from as they are not equipped to perform vertical takeoff. This type of UAS can vary greatly in price depending on flight time and payload capacity.

This is an example of a typical fixed-wing UAV.  This particular model has a payload capacity of 8kg and a flight time of 3 hours.  This image is courtesy of  the Center of Advanced Aerospace Technologies.  (Figure 1)

Helicopters:
     Helicopter UAVs are single rotary aircraft which means they contain a single lifting motor with two or more blades.  They come in both gas and electric and are capable of medium manage flight, though their range in heavily dependent on payload.  A typical electric helicopter can fly anywhere between 20-90 minutes, while a typical gas powered helicopter UAV may be able to fly between 4-5 hours for more expensive models.  Unlike a fixed-wing aircraft, helicopters are capable of vertical takeoff and the ability to hover to take detailed imagery.  The ability to hover also helps with the users ability to analyze real-time feedback.  Helicopters are extremely versatile due to being able to carry heavy payloads, fast, and have long flight times.

This is an example of a helicopter UAV.  This model has a payload capacity of between 5-7 kg, has 30 minutes of flight time for the electrical version and 1.5 hours for the gas powered version.  It comes installed with HD and infrared cameras.  This image is courtesy of the Center of Advanced Aerospace Technologies.  (Figure 2)

Multicopters:
     Multicopter UAVs are similar to helicopter UAVs, however they utilize over three separate lifting motors.  There is a large variety of multicopters ranging from systems with three lifting motors to systems with eight lifting motors or above.  This wide variety of model types allows for a large degree of flexibility in mounting a payload on the craft.  The large amount of lift sources provides more safety than the large blades of helicopter UAVs These systems can be extremely stable in strong wind conditions, however they require on-board computer systems to be flying.  Like helicopters, multicopters are excellent for hovering and taking detailed imagery of an area.  Multicopters have considerably shorter battery life than their fixed-wing or single-wing counterparts as they can only typically fly 20-30 minutes maximum.  Also, more arms typically means shorter flight time as the separate motors suck up more power.  The most popular model is the quadcopter; it has four arms and is seen as the least complicated, most user-friendly of multicopter models.

This is an example of a multicopter.  This particular model is a quadcopter and is one of the simpler multicopter designs.  This image is courtesy of AeroQuad.  (Figure 3)

Methods:

In this section of the report, the scenarios the class was given and the designed solutions and suggestions will be laid out and explained one by one.

Scenario One:
     A pineapple plantation has about 8,000 acres and they want to have an idea of where they have vegetation that is not healthy, as well as have an idea about when it might be a good time to harvest.

Pineapple plantations typically are placed in tropical climates where the pineapple plant thrives.  They are vast, flat expanses of land with low lying vegetation.  This particular image is of a pineapple plantation in Ghana.  (Figure 4)

The first step in solving this problem is determining how to tell if the vegetation is healthy or not. This can be done by looking at the reflectance of energy off of the various areas of the pineapple plantation. A typical way of looking at vegetation is using near-infrared energy (NIR). NIR has longer wavelengths than visible light and has some properties that allow it to be used for remote sensing applications.

Vegetation is a strong reflector of NIR, that is saying that when NIR hits the plant, it is mostly not absorbed. Half of it is transmitted through the vegetion, while the other half is reflected back off of the plant. This is caused by NIR hitting the plant and interacting with mesophyll cells. Plants with healthy mesophyll cell walls will reflect more NIR, while plants with unhealthy mesophyll cell walls will allow NIR to be transmitted through them (Figure 5).

This image shows the reflectance/absorption/transmittance of energy of a typical healthy leaf.  The visible red and blue light are absorbed by the leaf while the green visible light is reflected.  This gives vegetation its typical green appearance.  The IR is being mostly reflected in this image as this is a representation of a healthy leaf with healthy mesophyll cell walls.  (Figure 5)

The transmittance of NIR in unhealthy vegetation causes healthy vegetation to appear bright on an NIR camera, while unhealthy vegetation will appear dimmer. By monitoring the amount of NIR and visible energy reflected from vegetation is is possible to determine whether or not the vegetation is healthy (Figure 6).

The reflectance of NIR in healthy vegetation is much greater in healthy vegetation than in unhealthy vegetation.  This causes healthy vegetation to appear much brighter through an NIR camera than unhealthy vegetation.  (Figure 6)

The same concept of monitoring reflectance can be applied to determining whether or not the pineapples are ready to be harvested.  Pineapples that are ready to harvest need to be at least 1/3 yellow (Figure 8).  If the pineapple is still green throughout, it is not ready to be harvested (Figure 7).

This pineapple is ready to be harvested. (Figure 8)

This pineapple is not ready to be harvested yet. (Figure 7)

When analyzing a graph of visible light reflectance, which a camera would be able to capture, one would just have to look for areas of higher yellow light reflection in order to determine whether a particular area is ready to harvest or not.

In order to accomplish these tasks and obtain this imagery, a UAS can be used. When considering which type of UAS to use, it is important to consider the scenario. The pineapple plantation is made up of 8,000 acres which would be too large for a multicopter's short range to cover. Precision imagery is also needed of the various areas of the plantation, also there is likely no area for a fixed-wing aircraft to take off that would be nearby the plantation. This rules out fixed-wing UAVs. A helicopter with an infrared camera mounted on it would be a good option to capture the needed imagery. The gas engine would provide enough flight time to cover the entire plantation, while the maneuverability of the helicopter would do well in analyzing specific areas in real time.

A good option for this job is the Sniper Heli, it can be fitted with a wide variety of payloads up to 4kg including IR sensors, and if fully autonomous, which cuts down on needing to train a pilot. With the right mission planner installed in the craft it can go out and take images of the field without anyone even having to pick up a controller.


Scenario Two:
A power line company spends lots of money on a helicopter company monitoring and fixing problems on their line (Figure 9). One of the biggest costs is the helicopter having to fly up to the towers to see if there is a problem. Another issue is the cost of figuring how to get to the lines from the nearest airport.

Monitoring power lines using large helicopters and worker hanging out of them is an expensive and dangerous option which can be made unnecessary through the use of UAV systems.  (Figure 9)

A solution to this problem involves getting a UAV close to the power lines in order to take very high quality imagery. This immediately rules out using a fixed-wing UAS as it would not be capable of staying in one area to take the imagery. A multicopter would be a good option to perform the monitoring. Things to take into account in this situation are the location of the power lines. If the power lines are near a residential or area with a lot of wildlife or cattle, the multicopter should be required to operate at a low noise level so as to not disturb any animals or people.

The Aibot X6 was specifically designed with the idea of inspecting high voltage power lines. It has a 3kg payload capacity, is able to take high resolution digital images, thermal imagery to detect hot spots, and has excellent flight stability to insure safety around the power lines (Figure 10). This particular model also comes loaded with some of the most sophisticated mission planning software in order to insure a smooth flight each and every time.

The cage around the Aibot X6 helps prevent collisions with power lines.  It is one of the industry standards in power line inspection and would be invaluable when replacing the standard large helicopter inspection methods.  (Figure 10)

The cost of the Aibot X6 is rather steep at about $30,000 per multicopter, but the copter will pay off in the long run when considering how much the company is likely paying for a helicopter rental every time it has to go out and inspect the line. It's a pricey start up, but the reliability and safety of this model will go a long way to making the investment worth it.

One downside of using this multicopter is that the range is limited to 20 minutes of flight time. This can be problematic when considering that not all of the power lines will be easily accessible to a ground crew to get close enough with the Aibot. Due to this, it may be a good idea for the company to purchase a UAV helicopter as well. The Black Eagle (Figure 11) designed by Steady Copter is a solid option to supplement the Aibot X6 or replace it all together if the company decides. It may be less safe than the Aibot but it provides many of the same benefits while still being able to hover within 5 meters of a power line and having a much longer flight time of 3 hours. It is also cheaper,starting at only $10,000. The location of the particular power line or how the power lines are laid out would really determine which option the company would choose to go with or if they'd want to use both the Aibox X6 and Black Eagle to supplement each other based on their strengths.

The Black Eagle is a solid supplement or replacement to the Aibot X6 depending on the situation which may arise.  The Black Eagle would thrive when longer distances need to be covered to get to a power line more rapidly but is a slight downgrade in safety and software it is equipped with.  (Figure 11)

Scenario Three:
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 there is a better possible solution using UAS.

The desert tortoise is listed as "threatened" under the Endangered Species Act.  They are able to live as long as 60 to 80 years and can survive up to a year without access to water.  (Figure 12)

The desert tortoise (Figure 12) is a medium-sized tortoise which inhabits the deserts of the western USA. Desert tortoises live in some of the most extreme habitats in North America. The tortoises have been showed to be spread about in the Mojave and Sonoran deserts in a density of anywhere between 5 and 60 adults per square mile. Desert tortoises spend 95% of their lives in their burrows. This makes solving this problem not a matter of finding tortoises, but, mainly, of finding burrows. Desert tortoise burrow construction requires soil that can crumble while the tortoise is digging but will hold enough to resist collapse. Typically the proper soil is a sandy loam with varying amounts of gravel and clay. Tortoises really try to avoid sand as it will collapse too easily. Also, 97% of burrow locations have been found to be associated with shrub vegetation. The depth to a limiting layer is also very important in determining where desert tortoises may avoid placing burrows.

The area occupied by desert tortoises is vast and would require a fixed wing aircraft to go out and analyze quickly. The UAV would likely have to be gas powered in order to help it analyze as much areas as possible. The particular analysis it would be performing is using a multi-spectral scanner to search for shrub type vegetation using UAV and to determine soil type and depth using using visible-near infrared scanners. Tortoises have also been shown to live in areas where there are higher amounts of nutrients in the soil due to the fact that they have been shown to eat small rocks to gain minerals. Analysis of the soil using near infrared would make it possible to determine nutrient concentration in the soils. One other way to determine the location of burrows would be to use the thermal band of the wavelength spectrum (Figure 13) to find changes in ground temperature which may correspond to tortoise burrows. This type of analysis should be performed at dusk when the ground is starting to cool.  

This is the wavelength spectrum.  In order to determine locations of tortoise burrows a multispectral approach should be used.  This approach would involve using NIR reflection to determine shrub location and soil nutrient content and using thermal reflection to find ground temperature differences which may correspond to burrow locations.  (Figure 13)

By analyzing the data collected by the UAV, it will be possible to determine areas favorable to desert tortoise burrows and areas where there are actually burrows. The training could then be set to take place in areas which avoid the burrow habitat or are in areas which have been deemed uninhabitable for the tortoises (sandy areas, areas with no vegetation, or areas where there aren't a proper amount of soil nutrients). Areas where it's likely that there could be tortoises or where tortoise burrows were found would need to be further analyzed using more sweeps with the UAV or by the ground team.


Scenario Four:
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.

The Niger River Delta (Figure 14) is typically seen as one of the most polluted areas in the world. Between 1976 and 2001 there were almost 7,000 incidents involving oil spills. On average, around 240,000 barrels of oil a year are spilled into the Niger.

The Niger River delta is one of the most polluted places in the world.  This is in major part due to the large oil reserves in the area and the lack of care taken to extract and transport them.  The pipelines frequently leak causing environmental damage and causing the agriculture in the area to suffer.  (Figure 14)

This area is also one of the more dangerous locations in the world. This could make getting near to the pipeline to use low range UAVs difficult. The length of the pipeline may also warrant using a long range UAV. These facts point to a fixed-wing craft being the best option.

Thermal imagery is one way that can be used to try to find areas where there are leaks in the pipeline. A fixed-wing UAV would be released with a thermal imagery and visible spectrum camera on it. This should take place just after sunset when the temperature drops, this allows for better interpretation of thermal imagery. There should be a change in heat capacity of the ground in areas with oil on them and areas without oil (Figure 15). It is important to have both thermal and visual imaging to provide for better analysis. Another aspect to take into consideration is using a UAV with a motor that won't give off too much heat as this could skew the quality of the thermal image.

As can be seen in this thermal image of an oil pipeline, depending on the size of the oil leak, thermal imagery can do a good job in detecting oil leaks efficiently.  (Figure 15)

These scans would need to be done over time to get a good idea of where the oil leaks are and see the various changes in the locations of new leaks. Also, in order to determine whether there is subsurface leaking a 3D computer based thermal model of the buried pipeline and its surrounding soil could be created. This would take into account the various materials in the vicinity of the pipeline.

The Talon 240 is an electrical powered UAV with a battery life of up to 6 hours and a range of up to 20 miles. It can handle large payloads and the electric engine will cut down on the heat that would be generated if it were a gas engine. The Talon 240 is also quiet and can fly at a high altitude. This will help avoid the Talon getting in trouble from ground sources who might want to take shots at something flying above, seeing as this area in the Niger River Delta is very dangerous.


Scenario Five:
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.

The solution to this problem depends on several factors. How expansive is the mining operation and is it an open pit mine? Judging by the fact that the company doesn't have the money for LiDAR, this report will go forward assuming this is a medium to small scale open pit mine (Figure 16).

This is an aerial image of an open pit mine.  This is the type of imagery that would be initially needed in order to perform 3D analysis without LiDAR.  (Figure 16)

The first step would be to gather the proper aerial imagery. This imagery needs to be shot in sequence with a large amount of overlap between the images in order to create a good 3D image. The gathering of this data can be done using a multicopter or helicopter UAV. The multicopter or helicopter doesn't need to be of the highest quality it just needs to be able to capture the images every week to check the progress of volume removed. The relatively inexpensive 3DR Arducopter would be able to easily take images such as Figure 12. If price ends up being a huge issue, it is also possible to gather this type of imagery using balloons.

The next step in the process is to upload the image files to Photosynth.  This website will create a 3D image with point cloud data.  This data can then be extracted using a program such as SynthExport.  The data will now be in x,y,z form and can be brought into ArcGIS or a free product like MeshLab to create a 3D surface or mesh.  If in ArcMap use the "Surface Volume" tool which will give the area and volume of a raster or TIN surface above or below a given reference plane.  By setting the reference plane at a control depth, the change in volume can be analyzed each week to determine the amount mined by the company.

Discussion:

UAV systems have large variation and can provide many different solution to many different problems.  In the first scenario, a large pineapple plantation wanted to know how to tell if its crops were healthy.  This project required the use of a helicopter UAV using NIR imagery to display vegetation health.  The second scenario simply required a cheaper, safer option in order to monitor power line issues, this can be solved rather easily using a rotary-arm UAV with a high-definition camera.  Scenario three warranted use of a fixed-wing craft to determine soil type and nutrient concentration in order to find tortoise burrows.  The fourth scenario required a long range UAV fixed-wing craft using thermal imagery to find locations of oil leaks on a pipeline.  Scenario five then was a problem which concerned 3D analysis without LiDAR.  This scenario involved taking a large amount of simple imagery either from a rotary-wing UAV or a balloon and converting it to a usable 3D form using various internet programs.

All of these scenarios required more than just a level of understanding of each individual scenario, the UAV systems, and remote sensing imagery and analysis.  These scenarios required the ability to take every aspect of the situation into account and to put them all together.  They required the use of geographical knowledge of many different fields.  This is what is great about geography, it is so interdisciplinary and encompasses so much.  Geographic thinking and skills can be used to find leaks in pipelines in Niger or protect turtles in the Southwest United States and everything in between.

Conclusion:

This research activity encompassed many different fields and required a large amount of research to complete.  Advising the various companies in the wide variety of tasks wasn't easy.  Each scenario required a different approach, using different UAV systems, and different technologies in general.  This activity was an excellent way to get the class thinking about how they can best apply their learnt knowledge to real world activities and problems.