To begin mapping with Sequoia, you are first going to need power (5v, 2.4 amp). MicaSense has an adapter cable that will power Sequoia out from the Solo gimbal bay (as well as Phantom 3). It can be found here. It has been working well for me.
Micasense also sells a downward facing mount, which I recommend picking up. I have found that the fixed GoPro mount that comes with Solo adds some vibration to the RGB imagery and you have to stick the camera halfway out in order to plug in the Sequoia cables. It’s not as clean as the downward facing MicaSense mount and I found jello in my RGB imagery.
From there, I have just been mounting the external GPS to the center of Solo using velcro for easy swapping of batteries. I use a cheap velcro cinch strap that wraps around the vehicle for cable management. Next, I use Tower to plan the mission on my Android tablet mounted on the standard Solo controller mount. I design a standard Survey in Tower in the Editor. As they have not updated Tower with the Sequoia settings yet (still in the works), I select the Canon S110 at 80% front and side lap. It’s probably overkill but the stitches have been great, so I stopped experimenting with other cameras.
Sequoia works best at higher altitude flights. So I tend to fly between 40 and 100 m in my surveys, depending on the resolution I am looking for. What still remains to be seen is how fast you need to set the waypoints navigation (you edit these when logged into a powered-up Solo under Parameters and scroll down to W in the alphabetical listing) speed in Tower.
I fly at 500cm per sec at 130 meters and it seems to work well. At 30 m, I fly fairly slow at 100 -150 cm per sec. The primary concern with speed is the RGB, as it is on a rolling shutter, whereas the 4 bands are on a global shutter.
Next, you need to set Sequoia parameters. You need to power up Solo so Sequoia is also powered on. Instead of switching back and forth on the between Tower and Sequoia on the Android tablet wi-fi, I use my phone to log into the wifi on the Sequoia camera, to start and stop triggering, and set the distance I want the photos trigger at for 80% overlap at a given altitude.
I mainly use the GPS to trigger the Sequoia camera by distance. This distance is set in the camera app (there is an easy calculator), but you can also use intervalometer and single capture. Triggering by GPS though optimizes the number of photos taken (and there are a LOT with Sequoia).
When you have your mission designed and your camera parameters are set, then hit “Start Capture” on your phone for Sequoia, launch your mission on Tower using the Android tablet, and you are in the multispectral mapping business.
When the copter lands, log back into Sequoia wi-fi with your phone and hit ‘Stop Capture’. I tend to check the thumbnails in the Sequoia Gallery at that point to make sure my photos are there. If it is a really important dataset, I will download the photos to my laptop before I fly again just to be sure I have a backup in my data (e.g. if there is some malfunction in the drone at a later point).
In terms of post processing, Pix4D is necessary for stitching at the moment. Parrot worked closely with Pix4D on the Sequoia project. Pix4D can automatically handle the photos from the four bands, as well as a calibration panel and Ground Control Points if you want to use those. I have not used Photoscan or Agisoft, but I suspect the stitching won’t be great.
Pix4D will only stitch the RGB or the 4 bands within a single process, so you have to pick either/or for a given job. As I stated, for the 16 megapixel RGB camera, there is a rolling shutter. Pix4D is set up to deal with correcting the impacts of the rolling shutter.
I was impressed with how easy it was though to map with Solo and have that distance based triggering in Sequoia. Here is an example dataset from a forestry area in northern Montana (clearcut next to intact second-growth).