MAPIR Reflectance Calibration Ground Target Package

PIX4Dmapper PIX4Dmapper Questions/Troubleshooting
1

Hi Support,

The MAPIR package has three ground targets (color cards) that report the values 87% R, 51% R and 23% R. To calibrate the bands in Pix4D Mapper should I report 0.87, 0.51 and 0.23 as albedo values?

Is it sufficient to perform the calibration of the images in the Pix4D Mapper or do I have to use the MCC software they provide?

Please help me solve this problem.

2

Hi, Walter,

If by colour card you mean the calibration target ( the one presented here) you could use it as a calibration target for radiometric corrections in the software or I see that you could use it for post-processing in MCC. If you use it in our software then you should pick the one that has the profile closer to the reflectance you expect in your field.

For more information or step by step instructions on calibration target see: Radiometric-Calibration-Target

Cheers,

Ina

3

Hi Ina,

I thank you very much for your guidance…

but I need to know if I can use the values provided by the MAPIR radiometric target (87% R, 51% R and 23% R) by entering these albedo values (0.87, 0.51 and 0.23) in the Index tab Calculator to calibrate the bands.

I sent an e-mail to MAPIR and received this information: “We do not recommend using Pix4D for calibration since they only support a single target for calibration. We recommend running the orthomosaics through our MCC calibration process. If you still want to try using the albedo values you can look at the peak value in the target datasheet. The albedo values should be the peak reflectance at the peak of the transmission transmission wavelengths. The% R means that is the average reflectance value for that target material. We don’t offer support outside of our MCC application, sorry”

I’m new to PIX4D and I’m asking for your help to solve this problem… Forgive me.

4

Hi Walter,

As previously mentioned you could use this target with our software, I am not familiar with Mapir’s workflows and also not sure what does exactly is referring to multiple targets.

Given this could you please let me know what exactly the pre-processing of MCC is consisting of?

Thank you,

Ina

 

5

Hi Walter,

Could I ask you?
Did you solve the issue with the reflectance values and pix4d?
I will really appreciate it!
Thank you.

6

The reflectance factors should work. It is true that we support only one set of capture for the radiometric target and not multiple targets. However, if you have one flight or even two flights (with the weather conditions simiar), one set of radiometric targets could be used. For two flights, use the one captured after the first flight and before the second flight. In case, the sunlight varies a lot between two flights, process the projects individually (all the steps) and then merge in QGIS.

7

Hello,
Of course, we can capture the target anytime and depends on weather.
But the question is How to process these targets in Pix4d software during the processing.
Now, I’m making tests of different settings and calibration for the Mapir camera in Pix4d.
But, I’m looking if someone here had the experience on this matter.
Thank you.

1 Like
8

I am sure someone will reply. We have users who process Mapir camera images in Pix4D.