Drones to data

I’ve posted a lot of really pretty drone pictures and video these last six months and I’m realizing that this drone is actually pretty exciting tool for science communication. A reporter the other day said that she’d watched my Redonda video as part of her background research and it really helped her get a feel for the island. The original intent for the drone though was to capture high-resolution aerial photos of study sites to try to capture data on important but hard to measure ecological characteristics like vegetation cover, habitat availability, and maybe even habitat structure.

It’s a rainy Saturday in Boston so I decided to go back and look at some pictures from sunny Greece and see if I could start working with the drone footage to get some data.

The first step is actually capturing the video, of course, and that happened in Greece. I flew at a constant height (40m) in a straight line along the long axis of the island with the drone camera pointing 90 degrees straight down.

Here’s what that video looks like (don’t forget to click HD):

Now, that’s really pretty but for analyses I want a single, static image of the whole island. One option would be to just fly really high so the entire island is in the field of view. Unfortunately, since this island is so long, that’d have put me way higher than I wanted (or was allowed) to fly. This would also cause the resolution to suffer – I want to be able to see individual plants pretty clearly. The other option is to decompose that video, frame by frame, into a series of still images that I can then stitch together into a panorama.

This is actually pretty straight forward in in photoshop:

File > Import > Video Frames to Layers…

In this dialog box you select the video you want to make into still images and how many frames you want to skip per layer (the default is one layer every 2 frames). I chose one layer per 30 frames or approximately 1 image per second of video. That’ll give me good overlap to stitch the panorama together but not so many images that my poor computer will have to jigsaw hundreds of pictures together. You can then save those layers as independent images.

The final step then is just stitching together the panorama! Again in photoshop:

File > Automate > Photomerge…

Default settings worked great for me and voila, a beautiful high-resolution aerial photograph of an island in Greece.

Agios Artemios

Click on the image for a high-res look at Agios Artemios

So what about the data? I used my Oru Kayak seat as a launching pad on each of these islands. You can see it as the bright orange oval in the bottom third of the island. That orange launch pad is 80 cm across. With that I can set a scale that’s consistent for the whole island. I also know that the kayak is 360 cm long, which means I can check my calibration to make sure I’m getting good estimates. After that, it’s time to measure. I’m running out of time today so I haven’t made measurements but I’ll be calculating the  area of the island, the area of the green space, maybe even some metrics of patchiness, stay tuned!

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