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P4 Multispectral controller
493 10 2022-11-23
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dusanbuk
lvl.1

Serbia
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Hello to all,
I am new in the forum, I want to buy P4 Multispectral. What tablet/phone is recomended for P4 Multispectral I didnt find any details on DJI pages.
Thank you in advance
2022-11-23
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LV_Forestry
First Officer
Flight distance : 4726654 ft
Latvia
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Hi,Please see below the offical list of compatibility.Another option is to use UGCS with android device.
Ground Station Software | UgCS PC Mission Planning

Before you buy multispectral DJI product you must know that :
-The P4M is at end of his commercial life, replaced by the Mavic 3 Multispectral
-The RedEdge band of the P4M is unsuable as 730nm

So if your intention is to make NDVI then there are no problem, it is a good camera for this purpose. For more complexe job, think about something else.

Feel free to ask if you need more details
P4Mipad.png
source : DJI GS Pro - Download Center - DJI


2022-11-23
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dusanbuk
lvl.1

Serbia
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Thank you!
2022-11-24
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patiam
Captain
Flight distance : 1037995 ft
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United States
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LV_Forestry Posted at 11-23 13:35
Hi,Please see below the offical list of compatibility.Another option is to use UGCS with android device.
Ground Station Software | UgCS PC Mission Planning

Interested in more information/documentation of issues w/ the P4M RedEdge band...
2022-11-30
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LV_Forestry
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Flight distance : 4726654 ft
Latvia
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patiam Posted at 11-30 09:30
Interested in more information/documentation of issues w/ the P4M RedEdge band...

We realized this by comparing rasters made by ourselves with a P4M and rasters also made by ourselves with the Pika-L hyperspectral camera. I'll give you an example, on the same group of tree, on the same day, same resolution, a few minutes apart, we find an average NDRE=0.68 with the Pika-L, and NDRE=0.31 with the P4M.


You suspect it but I specify it for those who are not yet aware : DJI has never answered. On the other hand, the Pika-L is returned to the US for calibration, and on return the problem persists. So it's definitely a problem coming from the P4M images.

I have prepared something more visual for you below. Both rasters are normalized 0-1. I cut one raster to highlight the inconsistency of the data. Pika-L is on the Left / P4M on the right. Both are (NIR-RE)/(NIR+RE) rasters 840nm and 730nm.
NDRE.JPG

With NDVI the data tends to be identical so that the two rasters merge, the difference is not obvious at all.
NDVI.JPG

The NIR band is the same, so I conclude that the RedEdge is not on 730nm.

One day I may be motivated to extract all 600 bands from the Pika-L and find which one matches DJI's pseudo-RedEdge.

The first who will have the courage to buy the Mavic 3 Multispectral, wins a free analysis of his images to find out how many nm he was scammed. Feel free to contact me
2022-11-30
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patiam
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LOL.

Thanks so much for sharing this. I was not aware of it and have not tried NDRE (or really any indices or analysis using RE) w/ our P4M.

Presumably you shouldn't have to look at all 600 Pika-L bands... I mean it should be close at least, eh?

I do know someone considering purchase of a M3M... I'll let you know if they get one
2022-11-30
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LV_Forestry
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Flight distance : 4726654 ft
Latvia
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patiam Posted at 11-30 11:22
LOL.

Thanks so much for sharing this. I was not aware of it and have not tried NDRE (or really any indices or analysis using RE) w/ our P4M.

I try with closest band without success. What i can say is that by multiplicate by 2 the NDRE value from P4M its +/- good.
I mean, by walking fast, nobody can see the difference.

Of course by comparing with Pika-L data, you immediatly noticed that something is wrong.

Yes it would be very nice to get a M3M dataset to assess the quality. For the moment I give a "No GO" recommandation to people who are asking me about M3M.  This is only a precaution in relation to my P4M' experience, because I have never tried the M3M, I have never had a dataset.

@DJI: I challenge you to lend me one M3M to do a full data quality review. It's free enjoy it!
2022-12-1
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LV_Forestry
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Flight distance : 4726654 ft
Latvia
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I contacted PIX4D via their Youtube channel to discuss the problem of the P4M RedEdge band.


First they replied that PIX4D Field solves the problem by using a reflectance target.

Then I asked for an example raster. They went further by providing a raster from the P4M and a satellite raster, probably Sentinel-2.

Guess what ?

The result is the same ! On the right the NDRE raster from satellite images, on the left that of the P4M.
P4M NDRE Pix4Dfield.JPG

For the happy owners of the P4M: you have understood it, the RedEdge band obviously has a defect, for the moment I have not found any software which allows to obtain a quality result. I have already had the opportunity to mention it on the forum but I write it again here, a reflectance target is useless with the P4M. Note that all professional multispectral cameras are sold with a calibration file that allows you to use a reflectance target that has a very specific value. Where is the P4M calibration file paired with a reflectance target? I do have an idea...

For future potential buyers of M3M: Be careful, ask for datasets before buying to ensure that the performance of the product meets your expectations. Do not hesitate to come and ask questions on the forum. The vast majority of drone and software resellers are unfortunately not trusted people. They don't know anything about our business.

Update: obviously they are not happy.
Pix4DYT.JPG
P4M histo.png

For those who use multispectral imagery in the context of scientific research: Run away. Look for a camera that is calibrated correctly.

Thanks anyway to PIX4D for responding. Their software is in no way incriminated, I have the same problem with Agisoft Metashape. The problem is purely the RedEgde band of the P4M.
2022-12-8
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paul420
lvl.1

Algeria
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thanks for the infos !

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2022-12-16
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patiam
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LV_Forestry Posted at 12-8 08:13
I contacted PIX4D via their Youtube channel to discuss the problem of the P4M RedEdge band.
https://youtu.be/fGs_k8WG0PQ

Thanks once again LV_Forestry for looking into and sharing info on this important issue.

To make a strained analogy, without somebody validating the sensors in this way we (users) are all sort of like illicit drug users in that we are at the mercy of our supplier, trusting them that they are selling us what we need, but sometimes having unintended and undesirable results when they don't.
2022-12-30
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LV_Forestry
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Latvia
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patiam Posted at 2022-12-30 17:35
Thanks once again LV_Forestry for looking into and sharing info on this important issue.

To make a strained analogy, without somebody validating the sensors in this way we (users) are all sort of like illicit drug users in that we are at the mercy of our supplier, trusting them that they are selling us what we need, but sometimes having unintended and undesirable results when they don't.

You're absolutely right, if you don't have another sensor to validate the results, you have to trust what the manufacturer tells you. Pix4D's answer leaves me speechless. At the beginning the guy sells you the use of his software with a target of reflectance to obtain optimal results. In the end, yes you're fine, you multiply by two, compare the apples with the apples.

I've seen sellers of dreams but then he surpasses all the rest. I don't even want to know how their prescription maps are made. I imagine that for them a few tons/hectar is nothing, compare apple with apple. As long as the farmers pay for the recommendations. Just look at the studies done with control plots...

I still haven't had the opportunity to receive a dataset to see if the M3M holds up. No response from DJI, but that's no surprise.

If they were sure of their products it would be known. At the moment there is an upsurge of idiots who buy products because they are stamped "Pro" or "Enterprise" and who come here to cry because it does not correspond to their expectations.

Little message to reassure them: DJI doesn't care! You have paid, after-sales service is not included. This RedEdge band story is the perfect example.
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