Hi,

I've started doing some initial tests with my mavic 3E to see how DJI Pilot 2 works and the quality given by different settings. I usually take pictures in RAW so I can then color grade the pictures before creating the 3D model. The models I have to take are usually quite big, like squares of 300m each side at an altitude of 12m. So I tried to start the mission with the default speed and I had a warning that I should reduce the speed upto a maximum of 1.3m/s or I could loose some pictures, which would double/triple all the times (4h project becomes > 8h). As soon as I selected JPG this issue disappeared, which I guess is related to the processing/write speed.

My question is how good the JPG would be compared to RAW in case I would use it without touching it (I don't need millimeter precision and I have RTK which would help), my question is more on compression and later color grading, I would also avoid motion blur (the 3E camera has a mechanical shutter speed).

What max speed do you guys set on your drones when you take pictures to then make 3D models? Do you use RAW (accepting the slow speed) or JPG?

Thank you

Alvise

Ciao Alvise-

You'll probably find few folks here flying at such low altitudes- most are flying much higher to cover more ground (with coarser GSD). Just curious- what is the minimum altitude Pilot 2 will let you fly?

https://forum.dji.com/forum.php? ... D699%26typeid%3D699


I too have found that for very low altitude flight (< 15 m AGL) slow is the name of the game, both in terms of write speed & avoiding missed images, as well as to reduce motion blur (even with a global/mechanical shutter). Given the limitations of the systems, it is a trade-off, just like coverage vs GSD with respect to altitude. I will often choose the minimum speed of 1 m/s with my P4R when flying below 10 m AGL.

I don't have a feel for the difference in end product between shooting jpeg and RAW, but will say that again, the vast majority of folks shoot jpeg for mapping. I think you may have to do a test yourself to determine whether the added cost (in time) of shooting RAW and going so slow is worth the improvement in quality (if any). But you may also find that you need to go a bit slower than the default speed even when shooting jpegs when you get that close to the ground. There are also lots of variables like surface type, lighting, etc. that play a role here. The only real way to know is test.

Just curious- what is the minimum altitude Pilot 2 will let you fly?

is 12m, don't know why honestly.... maybe focus? It sets the focus to infinity so maybe all the image is in focus only at above 12m... but it's just a guess.

Yeah, I'll try to make some tests with different speeds. The default one is really fast... it was going at 25km/h, today was a sunny day so maybe it was ok...

Next test will be JPG vs RAW, with same model and same speed.
Ah, thanks for the link, I've started reading the thread

Well 12 m is much better than 25 m w/ GS RTK! From what I've heard as well as experienced, the minimum altitude in both apps is likely due to both DJI's assessment of camera limitations as well as covering their butts safety-wise (although with RTK, low altitude flight is much safer). At least in GS RTK one can use the "Relative Altitude" setting to get as low as needed. Does Pilot 2 have that as well?

Looking forward to hear your findings after running some test flights. Thank you in advance for contributing to the knowledge base here!

patiam Posted at 1-11 07:57
Well 12 m is much better than 25 m w/ GS RTK! From what I've heard as well as experienced, the minimum altitude in both apps is likely due to both DJI's assessment of camera limitations as well as covering their butts safety-wise (although with RTK, low altitude flight is much safer). At least in GS RTK one can use the "Relative Altitude" setting to get as low as needed. Does Pilot 2 have that as well?

Looking forward to hear your findings after running some test flights. Thank you in advance for contributing to the knowledge base here!

Yes it has relative altitude I would have to set a much higher overlap than the one suggested, but yeah this would probably to the trick. I'm now also testing UgCS to plan the mission, but I honestly would like to have a more complete official DJI software considering this is an enterprise product. Somethink I'd also like to have is some sort of desktop/web app where I can plan the mission (like dronelink), without having to plan the mission on the remote controller which is a pain when trying to set precise points and paths

Hi,

"My question is how good the JPG would be compared to RAW"
I only use JPG now, I find that the extra time to process RAW images is wasted. And the results are very good.


"at an altitude of 12m"
"I don't need millimeter precision and I have RTK which would help"
At this moment I don't understand. Why fly so low?


The 3D model will not be better, on the contrary you increase the number of photos, therefore the processing time, therefore the necessary resource...
The oblique mode is good when you have obstacles with complex geometry. If you fly the drone at 12m AGL I conclude that there are not many obstacles.


Tried to provide Pilot 2 or UGCS with a DSM, even with low resolution, and use terrain following at 50m AGL. The resolution will drop to 1.3cm +/-, but the 3D model will be of very good quality.


Afterwards, if you need to see under vegetation, on the sides of buildings... You need a LiDAR. I can't imagine watching the drone at 2m/s for hours to do 9ha!
At 12m you can't even hope to reduce the overlap, below 70% I doubt that the alignment will be done in good conditions.


I strongly recommend that you try at 50m, oblique or not, you'll see.


What photogrammetry software do you use?

LV_Forestry Posted at 1-11 09:16
Hi,

"My question is how good the JPG would be compared to RAW"

Thank you @LV_Forestry!


I use Reality Capture.


The reason why I'd like so low is not to get details of the mesh, but to get really good quality texture. It's not for survey precision but instead because I want to scan a kart track and bring it to a simracing software. It's a private place and it will be closed for a full morning, the track is quite flat without any obstacle so I will be able to fly at 5m no problem.The problem for sure is the number of pictures...

Unfotunately, the textures when taking pictures at 5m or even 8m are far better than at 12m or higher... at 20m-15m the details of the ground seem... like a bit blurry. But maybe I'm doing something wrong?

With the latest update can you still shoot RAW in oblique mode?