Quest Datahawk Drone

The only ones I'm hearing about much are DJI Phantoms. In a number of flavors. As best I can tell, the hobby market is ahead of the mapping (of course, contrary may be shown).

I think it's a practical starting point.

Also, handling, processing, and converting the data is a big deal.

Just what it looks like to me.

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We operate a Quest 200, which is the original larger version. The Datahawk was introduced as a smaller (easier to transport) version. Both are very robust machines, capable of sustaining quite a lot of operator misuse (don't ask me how I know!).

Both will easily map around a km square at 300 ft. height to give 3cm ground resolution in about 30 minutes (that's around 50-70% battery use depending on the temperature. We have flown ours in 40mph wind, although that isn't to be recommended for those with a weak heart.

You can get the Datahawk with a PPK card - theoretically you don't then need any form of ground control, but being a surveyor you will know that no control is not a good idea. If nothing else it provides an absolute check on what the PPK says.

The great advantage of the fixed wing over a rotary is that it has much better duration of flight and can handle wind in greater safety. We have flown over 3sq.km in a day, including putting down all the ground control. The downside is that you need more space to take off and land, but some of that comes with experience - once you are well used to it you can put it down pretty much on the chosen spot, but you do need a clear line in to the landing point.

Our experience is that manual landing is much better than using the auto-landing, once you have had a bit of practice. Auto take-off is great. Being quite large it is easy to keep in view during the survey, safety is good with several ways of getting it to come back quickly if a problem occurs.

Unlike some other fixed wings it is a modular construction, so if anything gets broken or bent then it just needs a replacement bit rather than a new airframe. Most minor damage you can repair yourself if you have a basic understanding and a few skills.

Data handling is straightforward - use Pix4D or Photoscan. Either will stitch together the couple of thousand images you get from 3sq. km. You will need good processing and graphics power on the machine you run the software on. The field laptop which controls the flight doesn't need the same power as it is simply handling telemetry.

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How do you handle the FAA line of sight requirement with the fixed wings on large sites?

Several ways. With a fixed wing it is easier to see so you aren't going to have problems loosing it at the edge of the permitted range.

Break the site up into smaller grids. Unlike a rotary a fixed wing will bank as it turns from run to run, so you get quite an additional area photographed beyond the grid itself. Thus adjacent grids don't need to overlap but can have a space between them which will be covered by the banking turns in the adjacent grids. Angled images aren't a problem for Pix4D or Photoscan.

If the site is open or with little obstruction, you can set several grids to follow each other and either walk up from centre to centre or drive up. If you walk a fixed wing needs to be put on an orbit hold for, say 5 minutes, while you walk up to the next grid. Or if the grids sit side by side you can walk across each as the aircraft progresses on each line.

Unofficially, and I don't know how the FAA view fixed wing turns, we set our safety circle to be 7/800 ft. to allow for any wind drift as it starts to turn, which means you can set the grid to almost 1km. lines on the assumption that you will walk up as the aircraft progresses (thus keeping 500m each way from the line centre).

Quest themselves have an extended line of sight permission and both the Q200 and the DataHawk are clearly visible at 1km. range. We have seen them fly up to 1.4km. - it needs close concentration but it is clearly visible.

In cluttered areas the limitation is likely to be ground obstructions which obscure the view - but the pilot and ground control operator don't have to be in the same place, as long as they can communicate. 100 metres apart makes a lot of difference to visibility and I guess the FAA don't say which of the two operators has to be within 500m. of the aircraft. With the Quest, the ground station can take over from the pilot in emergency, but is limited to redirecting to waypoints or instigating an auto landing.