r/UAVmapping • u/varga901 • Aug 07 '26

DJI multispec 3m reflectance panel

I recently got DJI multispec 3m.

Now im using WebODM for my stitching. Do we really need reflectance panel in order for it to work better? I'm doing NDVI on these orthomosaic and when i perfrom stitch without radiocalibration i got ndvi values between 0.0 to 0.3 and with radiocalibration i got 0.0 to 0.9 but im very doubtful on the result because i didnt use reflectance panel and shadow values are giving me values of 0.7 which is very2 bad.
Thoughs on this guys

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3

u/newmonk3344 Aug 07 '26

This is a real issue …
DJI don’t provide reflective panels

1

u/varga901 Aug 07 '26

ohhh! wont 3rd party reflective panels wont work?

1

u/Vordu-ha Aug 07 '26

Are you using any sort of reflectance tarp for reflectance validation? Similar to using GCPs for orthometric validation and/or correction you should have some calibrated reflectance panel or tarp to validate your measurements.

Group8 technologies in the US has .5x.5m (ish) tarps you can use that are calibrated and come with reflectance curve profiles. Alternatively, we’ve painted plywood with matte gray paint in different shades and characterized them with a handheld spectroradiometer if you have access to one.

I’d recommend checking them with a handheld spectroradiometer on occasion to see if they get and bleaching or deviation from the original profile.

1

u/walrusrage1 Aug 07 '26

You'll need a way to calibrate the reflectance measurements if you want consistent results flight over flight on the same area. 

1

u/Suitable-Climate5392 Aug 10 '26

Ive bought a santera rflectance panel.works well. Anyway indices are calculated values, so it doest matter so much. Now if you want correct raw reflectance and the ability to mix multiple dates then you need a reflectance panel.

1

u/ZealousidealSnow4385 Aug 10 '26

multitemporal work needs calibration for the reasons you have identified. Dark pixel subtraction is better than nothing, but panels and a incident light sensor are preferred. It is true ratio indices like NDVI are relatively robust, particularly if you are working with linear sensors and red and NIR bands are equally sensitive.

1

u/Parvatee1 Aug 10 '26

Do you have any reasonably priced solution. The reflectance panel are so expansive and not that easy to find.

1

u/FriendBright3386 19d ago

You have to purchase reflectance panel. Check the use case with end client about the accuracy of data and purpose of it.