but that seemed unnecessarily complex. I also have
experienced a fatigue failure of the camera mount I printed
a few months ago for the Fat Shark camera; I believe my
plastic was old and did not bond together very well. The
solution ended up being very simple. I placed the camera in
its protective case, attached it to a double-stick adapter that
came with the kit, and used zip ties to secure it to the
bottom of my ELEV- 8 quad (Figure 5).
The next step was to set up the camera to shoot
automatically. I’ll leave this to you because each camera
seems to have a slightly different menu system. After a
couple of minutes of searching through all of the menus, I
was able to find interval shooting and set it to two seconds.
There are a few other settings that you should look for
that I had to learn about the hard way. First, make sure the
date and time stamp is turned off. My camera had it turned
on by default and it resulted in some fascinating
reconstructions. Also, make sure that the camera resolution
is turned up as high as possible and that the memory card
is properly formatted so all of the storage space can be
utilized. Remember that a 10 minute flight (600 seconds)
will result in about 300 photos!
Finally, my camera had a beep that was supposed to
simulate the shutter sound. I turned this off as it became
excessively abrasive during bench testing.
After everything was set up, I did a “dry run” by starting
the camera and walking around the house with the drone. I
then went back and checked the photos to make sure they
were taking properly and didn’t have the time stamp, etc.
Now that the
mounted, it was
time to fly the
survey. I chose a
buildings and some
field. I wanted to
have a lot of open
space to fly without
being so worried
permission to fly
over the area, I
waited for a day
with low wind speeds and cloud cover so that there would
be minimal shadows. I made sure the camera was charged,
mounted it, and started the flight.
Since I didn’t program a flight path, I was trying to
make sure I had enough coverage by “eye.” I followed the
traditional pattern of “mowing the lawn”— much like is
done with side scanning sonar when mapping the ocean
floor (Figure 6). In the end, I could have flown a much
more aggressive pattern and mapped a larger area, but this
was fine with me for a first attempt. I systematically went
back and forth across the area at a roughly constant
altitude. In fact, I had to reduce my altitude at first because
I was actually reaching the cloud base and the camera’s
view was obscured!
After landing, I rushed back to the house (and
fireplace) to warm up and download the data. After
deleting the photos of me placing the drone and retrieving
it after flight, I had about 360 acceptable images. That’s
about 1.7 GB of data; nothing now, but a huge challenge
just a few years ago. I’ve made the images available for you
to use in a GitHub repository ( https://github.com/jr
leeman/ServoPhotogrammetry May17), as well as in a
ZIP file available at the article link.
Processing Images with ODM
Like last month, we will feed our images into ODM to
produce a mesh and orthophoto. Copy the images from the
“raw_images” folder of my data (or use your own) into the
“images” folder of our ODM installation. Next, we can open
a command terminal, navigate to that folder, and run our
Docker image. If you need help getting the installation
complete or spinning up Docker, be sure to check out last
month’s issue that goes into the process in detail.
14 SERVO 05.2017
Figure 5: Mounting the camera was as easy as zip
tying a mounting bracket to the base plate of the
quad. The swivel attachment let me start the interval
shooting sequence and quickly move the camera
back into place.
Figure 6: An idealized “mowing the lawn” pattern
might look something like this, starting and ending
at the green dot. In reality, my manual flight path
was a bit messier.
An orthophoto is an aerial photograph that has been
geometrically corrected or 'ortho-rectified' such that the
scale of the photograph is uniform and utilized in the same
manner as a map. An orthophotograph can be used to
measure true distances of features within the photograph.