Unmanned Aircraft — James Jaques-Watson Can off the shelf, cosumer level RPAs be used for typical agricultural mapping and surveying?

EXECUTIVE SUMMARY

The aim of this report was to investigate whether or not simple, off-the-shelf, consumer level RPAs could be used for agricultural mapping and surveying. Research was conducted through reading news articles and aviation websites to look at how the consumer level RPAs market has boomed in recent years and how RPAs are becoming more affordable. Data was also collected by venturing out to a local pineapple farm in order to test if a consumer level RPAs could map the area. This data shows an obvious spike in the number of recreational RPAs being purchased every year and how they are becoming increasingly common. The results show how clear a section of farmland looks in photographs taken by an unmodified DJI Phantom 3 Professional and how they can be used to map and survey the area. The report concludes that off-the-shelf RPAs can be a viable option for mapping and surveying farmland and other inaccessible areas. It is recommended that basic consumer level RPAs can be used for mapping and surveying farmland and otherwise inaccessible locations.

INTRODUCTION

Can off the shelf, consumer level RPAs be used for typical agricultural mapping and surveying? The Australian Certified UAV Operators Inc. defines a Remotely Piloted Aircraft (RPA) as “an aircraft, or aircraft-system, that is flown from a remote location without a pilot located in the aircraft itself" (Australian Certified UAV Operators Inc., 2017). In recent times, more and more of these RPAs or 'drones' are being purchased by hobbyists for recreational activities. In fact, the Federal Aviation Administration (FAA) in the United States prophesied that up to 1 million unmanned aerial vehicles would be sold during the Christmas season of 2015 (Peters, 2015). Since almost all of them have cameras fitted, some with up to 4K resolution, it should then be possible for these consumer RPAs to be used for more than simply giving enjoyment to amateur pilots receiving them as presents at Christmas. Furthermore since the most common unmanned aerial vehicles are multi-rotors, it is important to look at the principles of multi-rotor flight to see why mapping and surveying could benefit greatly through the use of remotely piloted aircraft.

The Principles of Multi-Rotor Flight

Multi-rotor aircraft, sometimes referred to as quadcopters because of the four propellers, require motors to give power to the propellers in order for them to turn at a rapid rate to create lift. All motors on a quadcopter are identical however, adjacent propellers spin inversely so that torques are balanced if all propellers are spinning at the same rate (Gibiansky, 2015). Pitch and roll rotation is controlled by increasing the speed of two motors on one side while slowing down the speed of the motors on the opposite side (Learn Robotix, 2015). All of these functions are controlled by the pilot from a Ground Control Station (GCS), most likely with a typical 100 milliwatt Flight Controller. RPAs pilots require their aircraft to be able to detect a minimum of 6-7 satellites to be able to double and triple-check its exact GPS coordinates and be flown legally.

Legal compliance is important and complying to the Civil Aviation Safety Authority's (CASA) air laws is mandatory. The following air laws apply to recreational RPAs and should be adhered to:

  • You should only fly in visual line-of-sight, in day visual meteorological conditions (VMC)
  • You must not fly closer than 30 metres to vehicles, boats, buildings or people
  • You must not fly over populous areas such as beaches, heavily populated parks, or sports ovals while they are in use
  • In controlled airspace, which covers most Australian cities, you must not fly higher than 120 metres (400 feet) above the ground
  • You must not fly in a way that creates a hazard to other aircraft, so you should keep at least 5.5 km away from airfields, aerodromes and helicopter landing sites
  • (Civil Aviation Safety Authority, 2009).

These laws are for safety reasons and should be followed in order to fly legally. With these laws in place, research and data can now be collected.

METHODS

Research was gathered through an expedition to a pineapple farm in Beerburrum West state forest. The task was to see if it was possible for an unmodified DJI Phantom 3 Professional, shown in Picture-1, to map and survey a section of pineapple plants. Starting from a home point near the plants' location, the RPAs was launched up to a height of 50 metres (~164 feet) and was carefully piloted above the field in order for picture upon picture to be taken. Later, the pictures would be knitted together to form a whole picture which mapped the region of pineapple plants. Finally, the whole picture would be examined for its clarity and its viability as a mapping tool. Secondary research was also collected through reading news articles and aviation websites to look at how the consumer level RPAs market has boomed in recent years and how RPAs are becoming more affordable.

RESULTS

Research into the cost of consumer level RPAs shows how DJI and other manufacturers are making them more affordable and more accessible for inexperienced and amateur pilots to purchase. This means that having your own RPAs is now easier than ever before with companies such as DJI, Parrot and 3DR now selling them for less than $1,200. The exact figures for these companies are compared with the standard prices of professional level RPAs below in Table-1, Table-2 & Table-3:

Tables 1, 2 & 3

To determine whether the Phantom's ability to take clear and concise pictures was successful or not, it was important to know the amount of pixels in each image. The camera from a DJI Phantom 3 Professional captures 12 megapixel images which DJI themselves claim "look crisper and cleaner than ever" (DJI, 2017). A 12 megapixel image is 4000 pixels wide and 3000 pixels tall. Although that's bigger than an 8 megapixel image, it doesn't necessarily equate to a better quality image (Gamet, 2015). A 12 megapixel image may have a higher pixel density but if the lens on the 12 megapixel camera isn't up to scratch, the image gets restricted to a lower megapixel count. Therefore if there is a great lens on the 8 megapixel camera, the image can be better then one that is 12 megapixels. The final resulting image taken of the entire pineapple farm is shown below in Picture-2 and Picture-3:

Picture-2
Picture-3

DISCUSSION & INTERPRETATION

It can be seen from the images taken by the Phantom's camera how much clarity there is from its 12 megapixel camera and how clear the picture of the pineapple farm layout turned out. Maintaining high quality pictures would be key in giving farmers an accurate measurement of the number of plants to a section. According to Low Ground Sample Distance (GSD), each pixel in the resulting photograph equates to a real-life span. GSD is calculated by dividing the width of an object, in this case the width of a tractor tyre, by how many pixels can fit inside the tractor tyre. Therefore, the Low Ground Sample Distance is 52 cm / 46 pixels = 1.1 cm. This means that the photograph's accuracy is down to just 1.1 cm which is very impressive for an off the shelf RPAs. This shows how plausible it is that an unmodified RPAs of its calibre could be used for mapping and surveying.

It is also important to consider the Phantom's flight time and battery life. The DJI Phantom 3 Professional offers about 25 minutes of flight time, up from the 10 to 15 minutes of flight time with the Phantom 1 (Dronefly, 2017). Although it has improved significantly, DJI Phantom's used to have a mean time between failure of 8 hours–whether that be due to low battery, pilot error or mechanical failure—because DJI RPAs are not built to a minimum standard (Mason, 2017). Having no minimum standard means that RPAs constructed by DJI are not bulletproof and therefore, are prone to their fair share of failure. Although the chances of failure are high, the improvements made to flight time by DJI over the years help to prove the capabilities of its Phantom 3 Professional as a viable tool for mapping and surveying.

CONCLUSION

There are so many considerations to take into account when flying RPAs with so many air laws and there is more to it than simply launching an RPAs and hoping for the best. It can be seen how plausible it is for farmers and even construction workers to use a basic consumer level RPAs as a tool for mapping and surveying. The final resulting image taken from the DJI Phantom 3 Professional shows the capabilities of this unmodified aircraft and how it can legitimately be used to aid farmers. It is a great privilege for RPAs pilots to be able to share the same airspace as manned aircraft and that opportunity might as well be used to make life just that little bit easier.

RECOMMENDATIONS

This report recommends that RPAs manufacturers such as DJI, Parrot and 3DR should create and sell RPAs specifically tailored for mapping and surveying. Additionally, mapping and surveying companies such as Austech, MNG, EMC and RPS Group should start employing RPAs pilots to aid them in mapping and surveying.

BIBLIOGRAPHY

Australian Certified UAV Operators Inc. (2017, January 24). What do we call them: UAV, UAS or RPAS? Retrieved March 6, 2017, from http://www.acuo.org.au/industry-information/terminology/what-do-we-call-them/

Peters, J. (2015, September 30). FAA fears that 1 Million drones could be sold this holiday season. Retrieved March 6, 2017, from Slate, http://www.slate.com/blogs/future_tense/2015/09/30/faa_fears_that_1_million_drones_could_be_sold_this_holiday_season.html

Gibiansky, A. (2015). Quadcopter Dynamics. Retrieved March 22, 2017, from http://andrew.gibiansky.com/downloads/pdf/Quadcopter%20Dynamics,%20Simulation,%20and%20Control.pdf

Learn Robotix (2015). How do Quadcopters and Multicopters fly? Retrieved from http://learnrobotix.com/uavs/quadcopter-basics/how-do-quadcopters-fly.html

Civil Aviation Safety Authority. (2009, October 21). Flying drones or model aircraft recreationally. Retrieved March 22, 2017, from https://www.casa.gov.au/modelaircraft

DJI. (2017). Phantom 3 professional - camera. Retrieved March 6, 2017, from http://www.dji.com/phantom-3-pro/camera#sub-feature

Gamet, J. (2017, March 8). How big is a 12 Megapixel photo? Retrieved March 9, 2017, from The Mac Observer, https://www.macobserver.com/tmo/article/how-big-is-a-12-megapixel-photo

Dronefly. (2017). DJI phantom 3 battery life review. Retrieved March 6, 2017, from Dronefly, https://www.dronefly.com/blogs/news/71731269-dji-phantom-3-battery-life-review

Mason, B. (2017, February 28). Group interview.

Credits:

Created with images by Unsplash - "drone sky camera"

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