Radiometric correction for Micasense Altum

Agriculture
1

Good day

Please could someone assist me with the following.

I have performed image pre-processing on imagery captured from a Micasense Altum sensor using Pix4d fields. The pre-processing of the imagery runs to completion and an orthomosaic and DSM are generated which look reasonable upon visual inspection.

However, after exporting the orthomosaic for further analysis in GIS software for e.g., ArcGIS it appears that the radiometric correction has not been performed correctly as the reflectance values are extremely high and more representative of digital numbers rather than reflectances. During the image import into Pix4d fields, images of the calibration panel were included so I am not exactly sure what could have contributed to the radiometric correction not being performed as expected.

Any assistance in this regard will be greatly appreciated.

Kind Regards

2

Hello @kiara.brewer.kb, Can you send us the quality report of the project so that we will have an idea about the issue? Send some screenshots showing the reflectance panel and reflectance factor you are using and the name of the reflectance panel that you are using. This usually has to do with the quality of the image or the calibration process nothing to do with the software or processing. Usually, the probable cause of getting the higher values is due to

  1. Not using the calibration panel or the panel images is not good.
  2. The reflectance factor is not used correctly.
  3. Make sure to use the reflectance map while comparing the values not the orthomosaic.

I would also recommend you to go through the below support article,

3

Dear Kapil

Thanks for your informative response and willingness to assist. Please see attached the log files, PDF report, and screenshots.

Kind Regards
48c8e810-5c08-4a9f-af74-09476d8e67b3_logfile.log (242.0 KB)
applicationLog.log (12.7 KB)
PDF_Report.pdf (747.2 KB)
CalibrationPanel.pdf (79.1 KB)

4

Hi Kiara,

I believe the issue here is you are pre-processing the imagery. Pix4Dfields does all the radiometric corrections so if you pre-process then process in fields you may be compounding errors in the data causing lots of issues. It also may strip the raw data of some of it’s necessary tags/information.

We high recommend not pre-processing any imagery because in many cases we are doing all the calibrations. Only a few exceptions exist for other manufacturers.

1 Like