UAS Phenotyping and Aerial Image Acquisition Procedures
From Poland Lab Wiki
- 1 Field-setup Guide
- 2 Flight Checklists
- 3 How-to Guide
- 4 Ground Truth and Agronomic Notes (Optional)
Ground Control Points
- ❏ Early in the crop growing season, distribute at least 12-15 ground control points (GCP) uniformly throughout the field.
- ❏ Six to eight GCPs should be installed in the outside periphery and the rest can be distributed uniformly inside the field, preferably, in the alleyways, at the row-column intersections for better visibility (Figure 1.2a)
- ❏ Survey the GCPs with either RTK or a DGPS GNSS systems (whichever available) multiple times during the season to reduce the day/time bias. For best results, we strongly recommend recording multiple readings per GCP to get the precise positioning values.
- ❏ Some GPS units allow recording of raw NMEA GNSS strings at high frequency (1-10Hz). Therefore, these units should be preferred, depending upon the availability. The averaged Latitude, Longitude, and Altitude readings can then be used in the photogrammetry softwares to generate highly accurate orthomosaics and Digital Elevation Models or DEMs.
- ❏ It is highly important not to move the surveyed GCPs from their fixed positions throughout the crop season.
- ❏ Generally, the white color GCPs are easy to spot, hence, should be preferred. Some photogrammetry softwares support automatic GCP detection. When available, these software customized GCPs can be used. Here are a few examples of GCPs that have worked well for us:
- ❏ Metal sheets screwed on top of the iron rods (Figure 1.2b)
- ❏ White color tile (12" x 12") placed on top of the brick/paver base: White tiles and bricks can be purchased from any hardware store. A base with 2-2.5" thickness should be preferred so as to avoid any dust deposition on the white surface. (Figure 1.2c)
- ❏ Place the reference calibration panel on a flat surface close to the first mission waypoint, at least 2-meter away from the plot (Figure 1.2d).
- ❏ It is very important to put the reference panels in the exact same orientation and position for each flight. This is to facilitate automatic processing of the panels based on coordinate positions. Small-size stakes/flags can be used to mark the corners of panels.
- ❏ These panels can also be utilized as a launchpad.
- ❏ In order to minimize the variations due to changing sun illumination and overcast, maximum aerial shots of calibration panel at regular intervals are recommended. This can be achieved either by using multiple calibration targets or by capturing images of a target at every landing and takeoff event during the mission (for bigger fields where multiple flights are necessary).
- ❏ A 15-20% gradient grayscale reference panel can be used as a reference panel. The details to build a reference panel are described below.
- Materials required:
- 1. 7mm thick lightweight plywood. 20 x 20inch (6 pieces).
- 2. Flat black and white water based color (1 liter each).
- 3. Wood primer (1/2 liter)
- 4. Paint mixing trays (6 units).
- 5. Brush rollers (6 units)
- 6. 100 ml liquid syringes with 10ml markings (2 units)
- 7. 5-7mm metal hinges with 2-3 holes (10 units)
- 8. Painters tape
- Materials required:
- UAS Accessory List
- ❏ Transmitter (Figure 1.1a)
- ❏ Radio with USB cable
- ❏ UAV batteries and battery chargers
- ❏ Extra set of propellers/wings
- ❏ Camera(s) with fully charged batteries
- ❏ Multimeter (optional)
- ❏ Toolkit (wrench set, propeller hex-key, camera mount screws and screwdriver etc.) (Figure 1.1b)
- ❏ Camera gimbal
- ❏ SD cards with CHDK installed
- ❏ Color calibration panel
- ❏ Ground Control Points installed in field
- Things to check before leaving lab
- ❏ An updated version of Mission Planner Software is installed on the field laptop.
- ❏ Has the field map been cached in the Mission Planner program? Details on map caching procedure are discussed below in section 2.4 (Note: This step is required only once per phenotyping field.)
- ❏ Does RC Transmitter have enough voltage? FrSky transmitter should have ≥ 9.4V charge.
- ❏ Are UAV batteries charged? 3-cell batteries should charge up to 12.6V.
- ❏ Is the laptop charged? Do you need/have a laptop charger?
- ❏ Ensure that you are familiar with the laws and regulations related to flying UAVs in your country/area. General laws in the United States require 400 feet maximum height and within line-of-sight flying.
- ❏ Make sure you have watched all the UAV manufacturer recommended tutorials before your first flight.
- ❏ When first flying your IRIS+, make sure to fly it away from populated areas and only in an open spaces.
- ❏ Before the first flight, make sure to perform a compass calibration otherwise this could lead to a bad behavior in GPS enabled modes. You can perform the compass calibration through APM or Mission Planner programs following this youtube video.
- Camera settings