Flight parameters and tips


Flight parameters and tips 

We recommend our Drone Partners to follow the flight parameters and tips below when performing any jobs for Aerobotics. These parameters are relevant for all orchard mapping standard flights and for most of the orchard mapping thermal flights. A separate section details the specific parameters to use when performing the orchard mapping thermal flights (i.e. Flying with the Altum).  


Parameters

Overlap 75%
Sidelap 75%
Weather Full sun or full cloud cover
Speed Between 9m/s and 12m/s depending on height
Height 
Small trees (0.5m - 1.5m): 80m
Medium trees (1.5m - 3m): 100m
Large trees (3m & above): 120m
Wind  Phantom 4 & similar sized drones: 20km/h

Matrice & similar sized drones: 25 km/h


Flying Tips

  • Always fly from the highest point.
  • Make sure you have a larger car that can handle the tough terrain of farms and be able to get from block to block easily.
  • Make sure that there is no more than 30m elevation difference per flight.
  • Fly between 9.30 am and 3:30 pm. Smaller trees or vines can be flown from 9:30 am. Bigger trees to be flown closer to solar noon. Start the day and end the day with smaller trees, which reduces the possibility of shadows. Bigger trees will have larger shadows for a longer portion of the day.
  • Don’t fly when there are rolling or scattered clouds. You can fly when there is full cloud cover.
  • Make sure the DJI drone camera is using default settings. 
  • Make sure your MicaSense camera is updated to the latest firmware. Check for the latest update here.
  • In between flights, load your data onto your computer and ensure that there are no defective or missing images. It is best to ensure everything is there before you leave the farm. You don’t want to get home and attempt to upload but have missing images or insufficient coverage. 
  • When selecting a boundary to fly, ensure you fly with a buffer so that there is enough coverage. Either pull the blue dots out or fly with a bigger flight path. Often the MicaSense camera misses a photo when it turns.
  • We have had cases of the power plug on the MicaSense camera losing connection. We recommend securing the cable with some putty or hot glue to ensure the vibrations during flight don’t cause the camera to switch off and miss images.
  • To make sure you have enough MicaSense MSP coverage from your flights, drop all the images into the Aeroview uploader in the field.
  • If the boundary is a triangle please redraw the boundary as shown below.

Ensuring the correct overlap

  • Getting the correct overlap of drone imagery is important to ensure successful data processing. Aerobotics requires 75% overlap and side lap (set through the Flight Planner App). However, this overlap is set relative to your takeoff point, thus where you take off from is important.
  • Please do NOT take off from the lower part of your mission. This will reduce overlap between images where the terrain is higher than the takeoff point.
  • Take off from near the highest part of your mission. This will increase overlap as the terrain gets lower than the takeoff point.
  • Make sure to fly one full boundary per flight and not capture half a boundary on one flight and the other half on another flight. This isn't always possible but please try to avoid this. 
  • A flight should never be carried out if there is more than a 30m elevation gain. The height above ground should never exceed 120m. Therefore, if there is a 30m elevation difference, you should fly from the highest point and set the height to 80/90m. If you are worried about lower resolution imagery when flying steep slopes, break the mission up into separate flights with different takeoff points.
  • When flying areas with steep slopes, it is best to fly along the contour of the slope.

Flying with the Altum

View or download the Aerobotics Flying with Altum PDF. 

The Altum sensor measurements are influenced by the internal state of the Altum sensor, including sensor temperature. To reduce that influence, we need all images over a single orchard to be captured with the Altum sensor under the same conditions. 

This section outlines a basic checklist of requirements for pilots to follow:

  • Flights are planned such that no block is captured in multiple flights. 
  • Flight boundaries are buffered enough to ensure all captures over the area of interest will be with the Altum facing downwards. I.e. not tilted for turning. 
  • Flights must take place within 3 hours of solar noon (±9:00am to 3:00pm). 
  • Flights are not taking place in patchy cloud cover.
  • Raw imagery is checked prior to upload to ensure there are no obvious shutter issues or blurry images.
  • If a single orchard is too large to fly in one flight, the battery change needs to be as swift as possible (pilot should plan to be near the battery change location).

All images for a block should be captured in a single flight

Conditions are most likely going to change between flights, so the most important step is to ensure that all the images captured over a single orchard come from one flight. That means no single orchard should be covered by more than one flight, but multiple orchards can be covered in one flight. 

If a single orchard is too large to fly in one flight, the battery change needs to be as swift as possible. The new flight should start within 5 minutes of the previous flight. This might mean that the pilot needs to get as close to where the end/start point of that flight is. 

All images captured over the block should be at nadir 

The thermal band is more sensitive to tilted fields of view, so it is important that no non-nadir (i.e. not facing directly downward) images are captured over the block. This means that the orchard boundaries should be buffered enough when flying that full coverage can be achieved without the “turning” images. 

The angle of the drone within the orchard boundary depends on the following: 

  • Speed of the drone 
    • The housing that holds the Altum is tilted at 7°, the speed should be set such that the drone tilts the equivalent amount during flight. 
  • The space the drone is given to turn 
    • Given the speed of the drone, it should be given enough space to turn such that no images are captured while the drone is (de)accelerating at angles off of 15°. 
  • Direction of the flight relative to the wind direction 
    • Under windy conditions, the drone should be flown perpendicular to the direction of the wind to maintain a consistent field of view when flying in both directions. 

Please see further details on how to ensure nadir imagery in the sections below. 

Flights must take place as close to solar noon as possible 

The closer the flight to solar noon, the better the quality of the data will be. Further to that, if flights take place early or late enough that there are objects (windbreaks or buildings) casting shadows over the crop, that data will not be usable for the farmer and may need to be reflown. The extent of the shadows should be assessed when flying further from solar noon. 

Altum shutter issue

Some MicaSense Altum sensors experience an issue where the shutter gets stuck closed after its calibration process, or gets stuck open when it should be closed to calibrate. 

When the shutter gets caught open, it produces the artefact seen in the images below, where there is a "ghost" of another image. 

When the shutter gets caught closed, all the pixels in an image will be the same with no image of the ground. Altum’s with shutter issues produce stitched maps that look like the following:

It was confirmed by MicaSense that the most common cause of the shutter getting stuck was due to dust/debris getting inside the camera. We would therefore highly recommend launching the drone from a dust-free area and use a 1m x 1m take-off pad to reduce the chances of excessive dust entering the Altum. This should be standard practice with all drone and camera hardware. Before each take-off it is vital to make sure that the entire lens is dust-free and clear of any fingerprints or smudges that may cause blurry images.

We also strongly recommend sending your MicaSense Altum unit back to MicaSense beforehand to get a gasket installed to prevent debris getting caught in the shutter. MicaSense have agreed to do this for free of charge for all Aerobotics pilots.

We would also like to encourage the general welfare and cleaning of all drone equipment. Taking time to make sure your hardware is regularly cleaned and maintained ensures consistent high-quality imagery and prolonged life spans of equipment.


Raw imagery should be checked before uploading 

An initial check should be done by the pilot to ensure that none of these artefacts exist in the raw imagery. The “closed shutter” should be easier to spot, since it will contain large numbers of blank imagery. 

Recommended flight settings to reduce non-nadir images 

Constraints with flying the MicaSense Altum: 

  • The camera is not mounted on a gimbal and is therefore affected by the pitch and roll angle of the drone. 
  • The camera is hard mounted to the drone at an angle of 7 degrees. 
  • The vertical field of view of the thermal camera as stated by MicaSense is 44 degrees 

Common causes of non-nadir images 

  • Images captured while the drone is braking or accelerating. During this time the drone’s pitch angle is at its most extreme. 
  • Flying parallel with the direction of the wind. In order to maintain a constant speed the drone’s pitch angle will either increase when flying into the wind or decrease when flying with wind. 

Boundary buffer 

In order to minimize extreme non-nadir images within the orchard boundary, a buffer is required. To calculate the boundary buffer, take the image overlap distance plus the drone’s braking distance. 

Braking distance = 1.3 x flight speed (tested on M210 v2, this may be different for other models) 

Image overlap distance = Flight altitude x 2 x tan(22) x (1-overlap%) 

Total buffer = image overlap distance + braking distance 

For example at 80% overlap and 12m/s flight speed


Flight height Boundary buffer
90m 30m
100m 32m
110m 33m
120m 35m
Example calc: buffer = (120 × 2 × tan(22) × (1 − 0. 8)) + (1. 3 × 12) = 35m. For example at 80% overlap and 120m flight altitude.

Flight speed Boundary buffer
9m/s 31m
10m/s 32m
11m/s 34m
12m/s 35m

Recommended flight speed 

Drone Flight speed
DJI Matrice M210 (v2)
7m/s to 12m/s

Note: real world conditions like wind speed and direction will have an affect on whether this results in the ideal pitch angle.

Instructions for reviewing raw imagery 

An initial check should be done by the pilot to ensure that none of these artefacts exist in the raw imagery. 

1. Download Metashape Professional here.

2. Open Metashape on laptop/pc. Select demo mode.


3. Drag & drop LWIR images from folder into Metashape. Eg. on Windows the easiest is to sort by file size then select the 45KB images. 

4. In Metashape in the photos tab, select "Details" list view and then sort by date and time.

5. Then select "Large" to see the image thumbnails. They will still look grey at this stage. 

6. Select Tools -> Set Raster Transform. Set Output Bands expression to "B1", and select "enable transform". Go to "Palette" tab on the same window. Select gray, click Update button, click "Auto" button, click Ok.

7. Thumbnails should now show more detail. Scroll through thumbnails to look for issues such as closed-shutter.