A reply to to Abhash regarding query of UAV technology

We, Geospatial Lab was queried about the various aspects of UAV. We have tried our best to clarify. The query by Abhash Maskey was :

Really neat website you guys have!

Some questions regarding the UAV
1. Was it the KUCopter that you used for terrain mapping? If not was it an open hardware, OTS component assembly you did or did you have a commercial UAV. Custom assembled UAVs, as far as I know, can be a real pain in the ass because you have to keep maintaining that stuff over and over again. At least, that’s what I have seen.

2. Did you have any telemetry on board to send data real time (you mentioned GPS, IMU or even the payload imagery) or did you just store it on board and then later retrieved it .
3. Did you guys have an autopilot or did you actually manually drive that thing up to 100m, because you know they might just fall off the sky.

Couple of questions regarding logistics/random stuff
1. Charging the LiPo batteries? in rural areas? how did you manage to do so
2. Repairs? did you guys have any issues with repairing, component loss or even crashes?
3. How heavy is it btw?

I have some further questions regarding some of the terrain challenges you faced:
1. Was the quad optimized for such terrain? what features do you think would better to have on such a multirotor.
2. Have you explored other sensors for terrain mapping?
3. Would low resolution 3D mapping be better than just a 2D on such terrains? Because 2D seems to be doing just fine as well.

feel free to take your time and answer them. I have a few friends here who might be interested in the work you are doing and might link you up with them. The issue is that staying here and trying to come up with a system design for Nepali terrain won’t do any good, so we need feedback from people who have actually gone to the ground and worked their ass off to get the data like the one above.

Please do include your email as well, I will be in touch
Regards,
Abhas

Reply to comment

Dear Abbhas,
We are sorry for replying you so late. We were very busy with UAV field work. Many thanks for your feedback.

As you many so many questions, we decided to answer them by email rather than through the post blog.

  1. We designed and procured individual parts and assembled them. We used commercial products. Flight controller board is from DJI NAZA (Wokoong-M). We designed it so that it can maneuverer with a sensor (camera or other depending on project requirement) weight Approx. 2kg. The details are as follows:

Table 1: Hardware Specification

Type : Multi-rotor
No. of rotors : 6
Flight Control Board : WooKong-M (50 waypoints)
Motor : Foxtech KV288 BLDC
Flight Data Recorder : IOSD MARK II
Electronic Speed Controller (ESC) : Platinum pro ESC 40A
Propeller Size & Pitch : 18 inch/6.1
Body Material : Carbon Fiber
Dimension (motor to motor distance) : 960mm
Radio Transmitter Signal Channel & Frequency : 8 channel 2.4GHz Radio System
Battery : 6-Cell LIPO Battery (22,000 MAH)
Self-Weight (including Camera Gimbal) : 6 Kg
Suggested Payload (Camera/Sensor) : 1.5 – 2.0 Kg
Camera System : xniteSonyA6000NDVI

Table 2: Operational specification

Max. Thrust : 20 Kg
Spatial Coverage : Approx. 2 sq. Km. (depends on flying height, camera configuration & battery)
Flight time : Approx. 20 minutes (depending on weight & wind conditions)
Flight Mode : Manual, Attitude & Autonomous (Waypoint Navigation)
Flying Height : Height limit can be set before flight
GPS/IMU Unit : DJI NAZA
Automatic  flight planning : Yes
Maximum Horizontal Speed : 25 m/s
Maximum Vertical Speed : 5 m/s
  1. Since we did not require to have real-time data for our current application, we decided not to include that feature with the current UAV. Images and other flight data are stored which are download and processed after the flight mission is completed. We have devices at sky end for telemetry but did not include such devices and display device at the ground end for the purpose.
  2. The hexa-copter can fly autonomously and we do fly with predefined flight which is prepared using Ground Station software. We need to provide camera details, overlaps, flying height and the coverage area to the software for route planning

Logistic/random stuff

  1. Yes, charging LiPo has always been a problem. We always take an extra LiPo battery. If we require more energy, we take small generator. However, this is very difficult option. Having extra battery is expensive but a better alternative as it saves your time as well.
  2. We have minor crashes a couple of times in the beginning. We were lucky because the damages were only on structural parts and nothing happens to expensive electronic parts and the flight control board. We repaired the copter in few hours with the spare parts we had.
  3. Weight: mentioned in above table

Question regarding Terrain issues:

  1. Multirotor is suitable for difficult terrain and for smaller spatial extent. The flight planning software takes 3D data from Google earth so that 3D flight plan is achieved; meaning flying height varies during the flight according to the terrain.
  2. We are using xniteSonyA6000NDVI sensor for forest monitoring. Sony A6000 camera is modified to capture information in Red, Green and NIR bands.
  3. 2D is not a replacement for low resolution 3D. In some application, visual interpretation for example, would suffix. However, for others you need to have 3D wich is not that difficult to obtain with overlapping images that you acquire with the UAV. We have not yet explored LiDAR for 3D data acquisition.

We believe that we have answered your questions. If any answer is not clear to you or do you have any further question, please write us back. We will try to answer them. Finally, we will be glad to work with people using unmanned platform.

Best Regards,
Geospatial Lab
Department of Civil and Geomatics Engineering
Kathmandu University

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