Reflectance Panel Instructions - Push Button Method
Reflectance panel images should be captured immediately before and/or after drone survey data collection.
Assemble aircraft, 6X sensor, and light sensor.
Power on aircraft.
Wait for 6X and light sensor status LEDs to turn green.
Place the reflectance panel in an open and unobstructed area.
Pick up aircraft and hold at waist height over calibration panel.
Ensure aircraft is not shadowing the reflectance panel.
Ensure the light sensor is not shadowed by your body.
Press the button on the light sensor to start calibration image capture.
Continue to hold the aircraft over the reflectance panel until image capture completes.
Set down aircraft and pick up panel.
Setup the aircraft, attach the light sensor and gimbal, then connect the light sensor to the gimbal.
Power the aircraft on. This will also power the gimbal, sensor, and light sensor.
Wait for the lights on the 6X and the light sensor to turn green to verify a camera session has been started.
In a clear area, open the reflectance panel and place it on a flat surface.
Try not to touch the gray calibrated reflectance surface with your bare hands or fingers to keep it free from contamination.
Lift the drone waist-high and centered over the reflectance panel.
Listen for beeps from the 6X Sensor and watch the LED lights on the camera. They will begin blinking green, then white, then turn solid green, which indicates the images were captured.
When holding the drone/sensor over the panel, avoid shadowing the panel, and try to keep the sun at your side, as opposed to in front or behind you when capturing the reflectance panel images.
Avoid shadowing the light sensor with your body.
Connect the Sensor to a laptop and check the current session folder for calibration imagery.
Use the same data offload process linked below to access the calibration images:
Pack away the reflectance panel, being sure to only handle it by the edges.
Once the reflectance panel images have been recorded it is time to fly and the imagery can be converted to reflectance values after the flight.
6X Multispectral Calibration Imagery Post Processing
When using a reflectance panel with the 6X sensor, raw images should first be run through the Sentera 6X Calibration script.
Follow the detailed usage instructions found in the README file.
Choose the correct option for your computer.
This creates an imgcorrect-venv environment that all scripts should be run in and installs the analyticstest library for the scripts to reference. If no errors appear, the imgcorrect library should be installed correctly.
you may need to add --user at the end of the install command.
The imagery correction in this repository can be used via:
Importing the various library functions defined in the package.
Running the pre-defined scripts with a Python installation of version 3.6 or above.
Running the standalone executable on the command line.
Path to image files taken from supported sensors. Choose the session folder of your images. This will cause the script to correct the images in each subfolders for all 5 multispectral band and ignore the rgb folder.
Identifier in the name of the image that denotes it is from the calibration set. If not specified, defaults to "CAL".
Path to output folder at which the corrected images will be stored. If not supplied, corrected images will be placed into the input directory.
If selected, Incident Light Sensor correction will not be applied to the images.
If selected, reflectance correction will not be applied to the images.
Overwrite original 12-bit images with the corrected versions. If selected, corrected images are renamed to their original names. If not, an extension is added.
Path to ExifTool executable. ExifTool is required for the conversion; if not passed, the script will use a bundled ExifTool executable.
If selected, scale of output values will be adjusted to 0-65535 and dtype will be changed to uint16.
The correction is done in 3 steps:
Autoexposure correction.
Incident Light Sensor correction.
Reflectance correction.
Sensors simulate longer exposures and wider apertures for subjects with lower upwelling radiance. These scripts correct by dividing pixel values by EXIF ISOSpeedRatings * EXIF ExposureTime
Downwelling radiance may change over the course of a flight as clouds pass overhead. These scripts correct by dividing pixel values by a rolling average of Incident Light Sensor readings (Camera:SunSensor) on images taken within 3 seconds of the corrected image. Correcting for ILS will standardize the DN (digital number) of your images based on the differences in incident light.
Sensors measure upwelling radiance, not reflectance. Radiance is dependent on unpredictable environmental conditions, and without a reference point with known reflectance, it is impossible to calculate. By beginning a flight with a photo of a panel with known reflectance, that panel's upwelling radiance can be used to standardize measurements.
These scripts correct by multiplying pixel values by slope coefficient (calculated based on known calibration panel reflectance values).
Use local data folders when running the proceesing scripts.
Reflectance Panel Instructions - Manual Method
The manual start for calibration imagery capture is a legacy feature for light sensors without the push button. If you have a Sentera light sensor without the push button, please contact support@sentera.com for an upgrade.
Reflectance panel images should be captured immediately before and/or after drone survey data collection.
Assemble aircraft, 6X sensor, and light sensor.
Power on aircraft.
Wait for 6X and light sensor status LEDs to turn green.
Place the reflectance panel in an open and unobstructed area.
Connect a USB-C cable to the USB-C port on the 6X, then to a computer
Open the webpage user interface.
Press the capture calibration button.
Remove the USB-C cable from the 6X.
Pick up aircraft and hold at waist height over calibration panel.
Ensure aircraft is not shadowing the reflectance panel.
Ensure the light sensor is not shadowed by your body.
Continue to hold the aircraft over the reflectance panel until image capture completes.
Set down aircraft and pick up panel.
Setup the aircraft, attach the light sensor and gimbal, then connect the light sensor to the gimbal.
Power the aircraft on. This will also power the gimbal, sensor, and light sensor.
Wait for the lights on the 6X and the light sensor to turn green to verify a camera session has been started.
In a clear area, open the reflectance panel and place it on a flat surface.
Try not to touch the gray calibrated reflectance surface with your bare hands or fingers to keep it free from contamination.
Connect the 6X to a laptop via the USC-C port on the sensor as shown.
Navigate to the 6X webpage.
Quickly disconnect the 6X from the laptop.
Lift the drone waist-high and centered over the reflectance panel.
Listen for a series of beeps from the 6X and watch the LED lights on the camera. They will begin blinking green, then white, then turn solid green, which indicates the images were captured.
When holding the drone/sensor over the panel, avoid shadowing the panel, and try to keep the sun at your side, as opposed to in front or behind you when capturing the reflectance panel images.
Avoid shadowing the light sensor with your body.
Connect the Sensor to a laptop and check the current session folder for calibration imagery.
Use the same data offload process linked below to access the calibration images:
Pack away the reflectance panel, being sure to only handle it by the edges.
Once the reflectance panel images have been recorded it is time to fly and the imagery can be converted to reflectance values after the flight.
Press the button on the light sensor to start the calibration image capture sequence.
For Gimballed Sensors
Connect the light sensor/GPS to the USB-C port on the gimbal
For Non-Gimballed Sensors
Connect the light sensor/GPS to the USB-C port on the 6X
For Gimballed Sensors
Connect the light sensor/GPS to the USB-C port on the gimbal
For Non-Gimballed Sensors
Connect the light sensor/GPS to the USB-C port on the 6X
