Autonomous Mapping with Quadcopter: HiveMapper

This entry is part 6 of 6 in the series Quadcopter
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I have played around with Autodesk’s photogrammetry tool, Recap Photo, in the past (here, here & here). These have been object scans with me walking around with my DSLR camera snapping away.

But there’s also an ‘aerial’ option in Recap which I have been clicking past, but I have a drone I can actually control. The sky’s the limit.

Subject 1: My house.

Mapping with HiveMapper

Rather than just manually fly around I wanted a way to set the Mavic Pro to follow a set of pre-planned waypoints autonomously and snap photos at set positions.

You can set waypoints in the official DJI4 Android/iOS app but its not really that practical for doing a survey since you need to fine-tune thing prior to pressing the Take-Off button.

Litchi, an alternative DJI controller, is a better option because you can import, edit and export flightplans on your big-screen PC using the MissionHub web-app.

This HiveMapper blog post explains the process in-depth and provides a base ‘lawnmower strips’ flight plan. Turns out HiveMapper does exactly what I am trying to do – it builds 3D map autonomously with aerial footage. Notably, it processes video rather than stills (Recap uses stills).

So I just followed the blog instructions and took a look at what HiveMapper can do. I’ll look into using Recap another day.

Lawnmower Flight Path

HiveMapper’s base lawnmower flight plan is in a csv file. In the Litchi MissionHub you can position it, scale it and edit it to suit. At each waypoint you can set an action (e.g. take a photo, tilt camera etc). For HiveMapper it starts the video, does the flight (~40 waypoints) and then stops filming, maintaining an altitude of 80m and camera tilt of 65° throughout.

I was a little nervous when I set the Mavic flying but it was all done in 2 minutes and back on my lawn (you can set it to home and land automatically).

HiveMapper processes the video with the flight plan data (cf. Recap with uses geo-tagged stills), so you upload the video (mp4) and your edited Litchi flight plan to the HiveMapper dashboard. NOTE see below: also upload SRT file

Once the files are uploaded it processes things at their end for a bit (actually quite a long time). Vid below is me panning around the result.

The result is a little meh, but let’s put things into context: I pressed a couple of buttons to get this result. My drone automatically did its thing for 2 minutes. The internet did its thing for a bit and BANG…its 3D model. That is kind-of magic.

A next attempt might include (if my dog permits…she HATES the Mavic):

  • THE MAIN ONE: Turn on subtitles/captions on Mavic. This creates an SRT (subtitles) file alongside the video file with flight metadata, which HiveMapper uses. It says you ought to do this in the instructions – which I skimmed & ignored.
  • A larger scan area: Just because bigger is better. Though bigger here would involve (possibly) breaking the law (more). So maybe not.
  • Less sun: I sent the drone up in the afternoon on a New Zealand full-sun day. The whole video was overexposed because of reflection off the roofs. Could probably fiddle with the settings on the camera too.
  • (Another dimension: A 3d lawnmower path, but not just at 80m) In brackets since not 100% sure.
Subsequent video with Mavic captions turned on. Adds a sub-titles (SRT file) with all the metadata from the flight – displayed as subtitles if you turn it on your video player.

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