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I recently bought a used Sequoia camera and when I bought it, I was under the impression that the sun irradiance sensor and calibration plate would calibrate all my images in real time and I wouldn't have to do a radiometric calibration. However, its not real time as the camera just records all the information to do the correction afterwards. I am familiar with GIS programs and raster calculators, and want to know if there are any open source plugins or documentation that already do this in QGIS, GRASS, SAGA, or even python and R. I'm not looking to buy pix4d or agisoft as I already own software to make a mosaic.

If not then what would be my best approach for accomplishing this?

I am familiar with what needs to be done from research but seek a good explanation. I am looking to produce an NDVI out of the imagery.

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The topic at the parrot website under reflectance estimation answers how to go about processing Radiometric Calibration of Sequoia Imagery. https://forum.developer.parrot.com/t/reflectance-estimation/5597/14

Also the applications link below also suggests the corrections that must be done if you require additional corrections and are the standards for the sequoia camera. https://forum.developer.parrot.com/t/parrot-announcement-release-of-application-notes/5455

Steps (Please comment if I am wrong)

Collect Metadata for Images

Images Normal Exif data

  • Exposure
  • ISO
  • FNumber
  • Yaw
  • Pitch
  • Roll
  • Sensor model A
  • Sensor model B
  • Sensor model C

Sunshine sensor Base64 Metadata

  • CH0 (Gain index)
  • CH1 (Gain index)
  • Yaw (Sensor)
  • Pitch (Sensor)
  • Roll (Sensor)

Radiometric Calibration per specific band (example: NIR) (Isq is Irradiance sequoia, Iss is Irradiance sunshine sensor)

  1. Apply Vignetting Correction to all NIR images
  2. Calculate average pixel value for target on calibration panel for NIR image
  3. Calculate average Irradiance value for target on calibration panel (Isq panel) for NIR panel image
  4. Calculate Sunshine sensor Irradiance (Isspanel) from the metadata in the NIR panel image
  5. Calculate K (K= Actual_reflectance_Panel * ( Isqpanel / Isspanel) (Produces coefficient for K for NIR)
  6. Calculate Irradiance of all NIR images (Isq images)
  7. Calculate Sunshine sensor Irradiance for all NIR image (Iss images)
  8. Calculate Reflectance for images using (R=K(Ips images/Iss images)cos(θ))
  9. Create ortomosaic for NIR band
  10. Perform all steps again on remaining bands
  11. Calculate vegetative indexs
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The radiometric calibration can be done with Agisoft Photoscan Version > 1.4. However there is no How to available. Here is a Forum Link with some useful information: Agisoft User Forum

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