Unmanned Systems Data Protocol and Format

Unmanned Systems provide the operator the opportunity to see the world from a completely new first person perspective. In order to achieve this, informational data must be able to be developed and sent to the operator but also stored for later use. This paper will be a detailed discussion of the data format, protocols, and storage methods used on the Mavic Pro, a small Unmanned Aerial System (sUAS) by DJI. It will describe each of the sensors onboard the system and the amount of power and storage they require to operate efficiently and work together into the overall data plan. Afterwards, an alternative data treatment strategy will be recommended to improve the overall operations of the system and enhance the experience of the operator.

The Mavic Pro is a foldable quad-copter sUAS and is the smallest system on the market from DJI. The Mavic Pro weighs 743 g and measures in at 83 mm tall, 83 mm wide, and 198 mm long when collapsed in its folded design (DJI, n.d.a). The Mavic Pro has a plethora of sensors onboard including: 5 cameras (4 for the dual forward and downward vision sensors and the main camera), dual satellite positioning sensors (global positioning system (GPS) and Global Navigation Satellite System (GLONASS)), two ultrasonic rangefinders, compass, and two inertial measurement units (IMUs) each containing the accelerometer and gyroscope (DJI, n.d.a). These sensors work onboard together to allow the Mavic Pro to be operated manually or autonomously while successfully avoiding obstacles using flight autonomy technology consisting of ultrasonic waves and Time of Flight (ToF) sensors to detect obstacles up to 49 ft away (DJI, n.d.a; DJI; 2016). An intelligent flight battery is the only power supply for the entire system, this battery is a LiPo 3S 11.4 V which can power the entire system for about 27 minutes of flight time (DJI, n.d.b).

The primary payload and visual system is a stabilized 28 mm camera equipped with a complementary metal-oxide semiconductor (CMOS) sensor to capture 4k video and still photos of 4000 x 3000 pixels in size (DJI, n.d.a). The camera is permanently fixed onto a 3-axis gimbal and comes with a removable cover that is used when the system is stored (DJI, n.d.b). When recording video or taking still photos, the files can be saved in two different formats depending on the needs of the operator. Photos taken with the system can be saved in either Joint Photographic Experts Group (JPEG) and Digital Negative (DNG) raw image form (DJI, n.d.b). The JPEG is a compressed image file that has discarded unnecessary data compared to the DNG which is unprocessed data but is in a format that many programs can read (Domeij, 2010). When recording videos with the Mavic Pro, the operator can choose to save the file container formats of either MP4 or MOV (DJI, n.d.b). There is not a significant difference between the two formats since they use the same lossy compression methods and can be easily converted to the other file type depending on the program the operator wants to view the video in (Joan, 2011). The data of the Mavic Pro saved onto micro Secure Digital (SD) card, the system comes with a 16 GB micro SD card, but the system can allow up a 64 GB card as long as it is a Class 10 or UHS-1 rating (DJI, 2017). The data can be viewed or downloaded onto a computer by using a Universal Serial Bus (USB) cable into a Micro USB port (DJI, 2017).

It is also possible for the operator to receive a live video feed as the Mavic Pro is flying. In order to this the operator will need to download the DJI GO 4 app onto a mobile device. This app allows the operator to control the Mavic Pro completely from the mobile device, but at the cost of range since it uses Wi-Fi versus radio frequencies to communicate with the aircraft (DJI, n.d.c). The Mavic Controller uses OcuSync transmission data to increase the range of the system up a distance of 4.3 mi (7 km) while using only Wi-Fi gives the operator a controllable range of 80 m (DJI, n.d.c). In order for the video data to be transmitted from the Mavic Pro to it is compressed through MPEG-4 AVC/H.264 which can offer DVD-quality video to the operator at under 1 Mbps (DJI, n.d.b; Rouse, 2005). This compression method allows the file to be broken down into a smaller size so that it can be sent at lower bit rates compared to previous methods, while providing the operator with a high quality video (Robertson, 2007).

One alternative data treatment strategy that could be considered for the Mavic Pro is to utilize cloud technologies. Cloud service technologies have expanded in recent years to include computing, networking and storage services (Hassan, 2016). If DJI created a cloud storage program to store video, still photos, and even flight data, the operator could conduct several flights without needing to go to a computer to download their data until they want to. The company would have the option to make cloud storage a subscription service to any registered owner and can change the rates by how much storage the operator would like to purchase. With the availability of stronger cellular and Wi-Fi networks, this option is becoming more feasible in the near future. An additional benefit of this option is that the operator would not have to select an option where more data could be removed and permanently lost such as truncation and other data treatment options.

References

DJI. (2016, December 13). Flight Controller. DJI. Retrieved from https://developer.dji.com/cn/mobile-sdk/documentation/introduction/component-guide-flightController.html

DJI. (2017, April). Mavic Pro User Manual V1.6. DJI. Retrieved from https://dl.djicdn.com/downloads/mavic/20170411/Mavic+Pro+User+Manual+V1.6.pdf

DJI. (n.d.a). Mavic. DJI. Retrieved from http://www.dji.com/mavic

DJI. (n.d.b). Mavis Specs. DJI. Retrieved from http://www.dji.com/mavic/info#specs

DJI. (n.d.c). Mavic FAQ. Retrieved from http://www.dji.com/mavic/info#faq

Domeij, U. (2010, August 10). Re: What is the difference of a DNG file Vs a JPEG file? [Web log post]. Retrieved from http://www.cambridgeincolour.com/forums/thread25500.htm

Hassan, Q. F. (2016). Innovative Research and Applications in Next – Generation High Performance Computing. United States of America: Information Science Reference. Retrieved from https://books.google.com/books?id=aZmqDAAAQBAJ&printsec=frontcover#v=onepage&q&f=false

Joan, B. (2011, July 11). Difference Between MOV and MP4. DifferenceBetween.net. Retrieved from http://www.differencebetween.net/technology/difference-between-mov-and-mp4/

Robertson, M. R. (2007, October 23). H.264 Versus MPEG-4 – Video Encoding Formats Compared. TubularInsights. Retrieved from http://tubularinsights.com/encoding-formats-mpeg4-vs-h264/#ixzz4eBNRTzOI

Rouse, M. (2005, September). H.264 (MPEG-4 AVC). TechTarget. Retrieved from http://whatis.techtarget.com/definition/H264-MPEG-4-AVC

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