How to perform Radiometric Calibration with Reflectance Plate without using Camera and Sun Irradiance information?

PIX4Dmapper
1

Dear all,

I have DJIP4 Multispectral datasets in the agriculture area.
I have 3 reflectance plates (10%, 20%, 90%) on the ground while the drone was captured.
The Camera and Sun Sensor were also on during the flight.

I would like to process the images with Pix4D, Ag Multispectral.
However, I want to process without Camera information (ISOSpeed, ApertureValue, ExposureTime) and Sun Irradiation (Irradiance, SunSensor).

Question 1: : Would it be possible to select Radiometric Processing → Correction Type: No Correction, while I still want to provide the Reflectance Factor of my Reflectance plates.

Question 2: : If the above answer is not possible. How to delete the Camera and Sun Sensor information from Exif and XMP? I have tried with ExifTool on Window and here are the results:

Camera:

  1. ISOSpeed: Can delete
  2. Aperture: Can delete on (fnumber, ApertureValue, MaxApertureValue) but not on (Aperture)
    I am not sure which Aperture value does Pix4D uses for the process.
  3. ExposureTime: Can not delete, only possible to set to 0.

Sun Sensor:
Irradiance, SensorGain, SensorGainAdjustment, SensorIndex, SunSensor, SunSensorExposureTime, IrradianceExposureTime: Can read, but can not delete:

exiftool -xmp:Irradiance DJI_0011_2020.TIF
exiftool -xmp:Irradiance= DJI_0011_2020.TIF

Warning: Tag 'xmp:Irradiance' is not defined
Nothing to do.

Question 3: : Which Reflectance Plate (10%, 20%, 90%) is the best (make the best sense) on Agriculture area for Vegetation Indices.

Very thanks in advance for your comments.
Konlavach

2

Hi,
Thanks for your patience. Regarding your questions:

Question 1: It is not possible. If you select the No correction option, then the option to import reflectance panel images is disabled.

Question 2: You can try using exiv2: https://exiv2.org/
You can create a .bat file using the following info:

@echo off
for %%v in (*.TIF) do (
	echo %%v
	exiv2 "-Mreg Camera http://pix4d.com/camera/1.0" "-Mdel Xmp.Camera.IrradianceGain" "%%v

)

Question 3: I am not sure about the reflectance plates you have. Can you send some images? Or give me more details about them?