3DR Solo as an Ag Survey Tool
If you’ve got a 3DR Solo, a gimbal, and a GoPro, then you’ve also got an agricultural survey drone. This post will describe how to use your GoPro and Solo to do agricultural mapping.
What you need:
1) Solo drone.
2) Solo gimbal.
3) GoPro camera with a non-distortion lens (no fisheye). We also recommend a camera with an NIR filter installed. This will enable you to generate advanced products like NDVI and Variable Application Report maps.
4) Ground control station (GCS). This can be either a Windows PC with Mission Planner or an Android device with Tower.
5) FarmLens Uploader installed on a Windows PC. Get this free from the FarmLens ‘Downloads’ menu, here.
6) A subscription to FarmLens. This is where the image processing happens.
How to survey:
First, you create a survey pattern over your target field using Tower or Mission Planner. With this pattern uploaded to your Solo, it can then fly over the field while the under-mounted GoPro takes picture of the ground the entire time. During the survey, you need to maintain an uninterrupted telemetry connection between your ground control app (Tower or Mission Planner) and the drone. This will be important for post-flight photo formatting. When your survey flight is done, use FarmLens Uploader to format your photos and upload them to FarmLens for processing. Once your upload to FarmLens is complete, your photos will be stitched into a single image of your field in a matter of hours. After you crop this image to your preferred dimensions, your final products will be generated within a few minutes. For a more detailed explanation of this process, see this page.
If you’re already well-versed in Solo operation, you’ll find this process quite simple. However, there are some key tricks to getting the best results from your survey flight…
Ensure GoPro and Solo firmwares are up to date. Also, make sure you are using the correct flight parameters to achieve your desired survey products. See this page for details on the various survey types.
The time must be perfectly synched between the GoPro camera and the GCS device prior to flight. This is absolutely necessary for accurate post-flight photo geotagging using the FarmLens Uploader (FLU) application. FLU geotags your photos by comparing their times to the corresponding times in the flight’s telemetry log. This telemetry log is recorded on the GCS during flight and it includes the latitude/longitude coordinates of the drone at any given time during the survey flight. If the camera and GCS clocks are not precisely synced, the photos will be tagged with inaccurate lat/long coordinates. This will degrade the quality of the survey’s final product.
See ‘Synching the GoPro and GCS Times’ below for details.
The camera must be powered on, installed in the gimbal, and connected via the mini-HDMI cable. But the function must not be started.
See ‘installing the GoPro’ below for details.
The gimbal must keep the camera pointed straight down (0º).
See ‘Orienting the Gimbal’ below for details.
The survey pattern uploaded to the drone must include camera trigger commands before and after the core survey pattern. This will start and stop the camera’s function at the appropriate time so that you don’t get any conflicting photos in your set.
See ‘Integrating Camera Trigger Function’ below for details.
A single survey must consist of a single contiguous photo set which falls within the time frame of a single telemetry log.
For details on matching photo sets and telemetry logs, see ‘Creating Survey Data Sets’ below.
Synching the GoPro and GCS times
This differs depending on whether you are using Tower or Mission Planner as your GCS software.
If you are using Tower, you’ll be using an Android device as your GCS. The best way to sync your GoPro and Android device clocks is as follows:
- Install the GoPro App on your Android device.
- Use the GoPro App to connect to your GoPro via WiFi. Follow the instructions in the App.
- The instant you connect to the GoPro through the app via WiFi, the Android and GoPro clocks will automatically synchronize. There will be no indication of this. It just happens
If you are using Mission Planner, you’ll be using a Windows OS device as your GCS. In this case, you’ll use the application, GoPro Studio, to sync your camera and GCS times.
Install GoPro Studio on your Windows device.
Open GoPro Studio.
Connect your GoPro to your Windows device via USB cable.
The instant your GoPro is connected, it’s clock will synchronize with your Windows GCS. There is no indication of this. It just happens.
Installing the GoPro
In order for reliable survey function, you must be careful to properly install your GoPro into the Solo’s gimbal.
a. Power the GoPro on, but DO NOTstart the camera’s function. In other words, don’t press the shutter button to start it taking pictures.
b. Ensure the GoPro is in it’s default state, the WiFi is off, and it is not engaged in any functions.
c. Install the GoPro into the gimbal.
d. Plug in the gimbal’s HDMI cable.
Orienting the Gimbal
a. Use the Solo’s RC controller to orient the gimbal straight down.
b. This will be indicated on the controller’s screen as ‘0º’.
c. The gimbal must maintain this orientation for the duration of the survey flight. Any deviation will result in poor results or absolute failure.
Integrating Camera Trigger Function
The camera trigger commands will be integrated into your survey pattern by default in both Mission Planner and Tower. If you generate a ‘Survey (Grid)’ pattern in Mission Planner or a ‘Survey’ in Tower, camera trigger commands will be automatically inserted in the waypoint/command series immediately before the first waypoint and immediately after the final waypoint. DO NOT change this. This causes the camera to start and stop at the ideal times so that you will get clean survey results. To ensure that you have these camera trigger commands, follow these steps for Mission Planner or Tower.
IN MISSION PLANNER…
a. Make a polygon around your target survey area.
b. Right click, go to Auto, then select ‘Survey (Grid)’
c. Create your survey pattern.
d. Bring up the waypoint matrix from the bottom of the screen.
e. Here, you will notice two commands near the beginning and end of the waypoint series called ‘Do_Set_Cam_Trig_Dist’. These essentially trigger the camera’s shutter button, starting or stopping it’s function.
a. In the Editor view, make a Survey.
b. Upload the survey to the Solo.
c. Once the survey has been completely uploaded, you should be able to view the individual waypoints and commands that constitute the survey. These will be displayed as green square icons along the bottom of the Editor display.
d. Within the waypoint/command series, you should see two items with camera icons near the beginning and end of the survey pattern. These are the camera trigger commands.
Creating Survey Data Sets
Once your survey is complete, the photos need to be geotagged before they can be uploaded to FarmLens for processing. This is one of the functions of FarmLens Uploader (FLU). It does this by comparing the timestamp on each photo to the corresponding time in the telemetry log from your survey. The telemetry log has a record of the drone’s latitude and longitude coordinates at any given time, so FLU copies these coordinates to each photo. This is why it is imperative that you sync the camera and GCS times before your survey.
You also need to have a single contiguous photo set to match up with a single telemetry log. This constitutes one data set. In order to reliably create a single data set from your survey, consider the following:
- FLU identities a single photo set as a series of photos with no more than 60 seconds between consecutive photos. So 60 seconds of latency will mark an end or beginning to a photo set. This will be done for you, since the Solo will trigger the camera to start and stop automatically immediately before and after the actual survey pattern.
- A new telemetry log will begin recording when you ‘Connect’ to the Solo through your ground control application. This log will end once you ‘Disconnect’. To ensure that you have a single telemetry log to match the single photo set from your survey, make sure you do not disconnect/reconnect during the survey.