Let this sketch run for a few minutes and then remove
the SD card, verifying that there is a data file there with
Flying the Survey
With completed hardware and firmware, all
that’s left is to attach the sensor package to our
drone and go collect some data! I used double-stick
tape and Velcro™straps to attach the Wildfire and
breadboard to the H-Quad’s flight deck (Figure 8).
The sensors were taped to the side of the frame,
facing down (Figure 9).
For power, I tied a 2. 5 mm power plug into the
power distribution board of the quad and fed the
battery voltage straight to the Wildfire, which
accepts 7-12 VDC (Figure 10). A small USB battery
would also be an easy way to power-up your setup.
With everything set up and running, I was ready
to fly the survey. First, make sure the SD card is
inserted — there is nothing worse than flying a
survey and (upon landing) realizing there is no data. Similar
to the photogrammetry surveys we flew back in April/May,
we want to do a “mowing the lawn” pattern. The height
and line spacing directly affects the resolution and flight
If your quad can be programmed to fly to waypoints,
program a grid over your survey area. Otherwise, try to fly
a good coverage pattern manually. As always, be sure that
you are not breaking any of the FAA rules about altitude,
proximity to airports, etc. I found a park with some
sidewalks that was a great place to collect some data
(Figure 11). I was able to walk around the circular sidewalk
and performed a hub-and-spoke like survey pattern.
The survey itself took about 10 minutes of weaving
back and forth, hoping that nothing was vibrating loose
and that data was being written onto the card. After
landing, I anxiously pulled the SD card and found a file with
all of the data. Happy, I packed up the flight gear and
headed back to the house.
Plotting the Flight Path
Once you have your hands on the data file (or use
mine from the repository), we need to do a little QC on the
data. Open the file in your favorite text editor and inspect
the header. If it is poorly formed or partially written, replace
it with the correct header: “DATETIME,LAT,LONG,ALT,SPD,
COURSE, NSATS,TA,TO,CR,CG,CB.” Also look at the data
SERVO 08.2017 35
Figure 10: Extra tie-in points on the power distribution PCB made it
easy to add a 2. 5 mm DC power jack to power this and any future
Figure 11: This city park with a circular sidewalk should
provide a nice thermal contrast in the late afternoon. We
would expect the sidewalk to be warmer than the grass
in the center.
Figure 12: Add a header to the CSV output file and remove and pre-takeoff/post-landing rows. The cleaned data file is ready for analysis.