Processing Micasense

PIX4Dmapper PIX4Dmapper Questions/Troubleshooting
1

 Hi all- 

 

I am new to pix4d and would like to know the workflow for processing micasense imagery. 

As you should know, with the micasense (last year’s model) you image reflectance tiles on the ground before and after each flight. Can these be incorporated into the pix4d processing for radiometric correction?

 

The dataset I now have had striping and shadowing from inconsistent cloud cover- the micasense server couldn’t eliminate this so I am wondering how pix4d would do.

Right now I generated a reflectance map and ortho but I still have inconsistent lighting so perhaps I am missing a step.

 

Thanks in advance-

 

Alex Graham 

2

Atlas does a better job of handling micasense imagery than Pix4d  (at this time). 

The solution for inconsistent cloud cover during the flight is not a different processing platform or method, it’s re-flying.  

Maybe (hopefully) that will change in the future. 

3

Hey Alex, Hey Derrick,

 

It is possible to process Micasense magery. You can use the radiometric calibration target. 

Here all the details: https://support.pix4d.com/hc/en-us/articles/206494883 

and here you can see how to calibrate and correct the image reflectance, taking the illumination and sensor influence into consideration:

https://support.pix4d.com/hc/en-us/articles/203891879

Since your dataset has striping and shadowing from inconsistent cloud cover, it is possible to see the effects in the outputs, but we encourage you to give it a try. 

 

Best Regards, 

4

Hi guys, 

 

I am aware of the reflectance target calibration settings, but my challenge is knowing what those albedo values are. 

 

For the flight I am referring to with the inconsistent cloudcover, we did not have the DLS (downwelling light sensor). We do not know the albedo values of the imaged tiles. The default values in pix4d are set at 0.5… not sure what I should enter for each band. 

Now, certainly albedo would change depending on the scene, time, cloud cover etc. But I just want to know standardized, generic albedo values considering a cloudy day, and a sunny day. Micasense doesn’t have this info for me… what values have you guys entered??

 

Thanks 

Alex 

5

Dear Alex,

The albedo value of your calibration target is a characteristic of your target. It does not depend on time/cloud cover. The total amount of light reflected does depend on this, but not the albedo value (you can think of it as percentage of light reflected). Since this value does not change, it can be provided by the manufacturer, and this is whom we suggest you contact to obtain the albedo value at the different wavelengths you are measuring. These values need to be inputted and the default values in Pix4Dmapper are more of a placeholder: they do not indicate typical values. You should input the values of your particular target.

We recommend flying under constant lighting conditions (not scattered clouds) as this introduces artefacts in the computation that are very difficult to handle.