If the focus of your survey is primarily the fidelity of the DSM (topography), then you want to use the nadir mission type.
If the the aesthetic of the 3D model is the primary goal, then the oblique mission is correct.
M4T RTK accurate or not ..
- Thread starter Mflyer
- Start date
If the the aesthetic of the 3D model is the primary goal, then the oblique mission is correct.
Thanks. In this case the focus of the survey was to test the accuracy of M4T with RTK (I've used Base+Rover approach - DJI RTK3 + M4T). Because I've seen here different results from what I've obtained I was wondering where I was wrong.
At this point in the state of the processing technology, nadir image sets provide more accurate z values.
@jaja6009 error results for z on the M4T / Oblique without GCPs was over 1 foot. So worse than your 20cm. With GCPs, it dropped to .7 feet (21.34cm)
Attachments
I refer to this test
Test 1 Nadir Images with Altitude Optimization, 5 Check Points, No GCPs.
X: 3.14 cm, Y: 1.95 cm, Z: 8.14 cm Total: 8.93 cm
Test 2 Smart Oblique, 5 Check Points, No GCPs and we have a winner!
X: 1.98 cm, Y: 1.98 cm Z: 3.26 cm Total: 4.29 cm
Test 1 Nadir Images with Altitude Optimization, 5 Check Points, No GCPs.
X: 3.14 cm, Y: 1.95 cm, Z: 8.14 cm Total: 8.93 cm
Test 2 Smart Oblique, 5 Check Points, No GCPs and we have a winner!
X: 1.98 cm, Y: 1.98 cm Z: 3.26 cm Total: 4.29 cm
I would consider that result, i.e that the smart oblique was better, as an anomaly comparing it to all of the other tests. Not the standard. Your own text confirmed that the nadir set produced better results. You need not take my word for it. Do a dozen more tests on your own and confirm it for yourself.
Thank you. This is because oblique images (from Smart oblique) "confuse" more the photogrammetric process than just a few obliques in the "elevation optimizatione" mode ? Would it be better using the M4E ?
I'm not sure as to the "why". It may be that there are more variables for the processor to deal with using obliques compared to nadir images. Less similarity between potential tie points for example. But I don't really know.
Over all, the M4E would be a better platform if topography is the goal. If all else is the same, position accuracy, and image time stamping, etc., the M4E has a global shutter. But no thermal, obviously.
Over all, the M4E would be a better platform if topography is the goal. If all else is the same, position accuracy, and image time stamping, etc., the M4E has a global shutter. But no thermal, obviously.
I used the Smart Oblique where the drone takes several images for each position, a nadir and several obliques.
You used the 5 Flight Lines Oblique.
What software are you using for processing?
And I don't really have any insights yet as I am still testing by trying to map different areas.
When I run the data in Agisoft Pro, Pix4Dmapper and Drone Deploy, the results are very similar.
The 4E is going to be the better mapping drone period. The camera is much better in every aspect. Its just providing the photogrammetry software with more and better information in each image.
I still have to map 2 more areas, at school and my beach project. I will try to have the 4T map both to see how it fares.
I really would like to know from DJI engineers why the 4T fares worse in mapping. It seems like it is something more than just the mechanical shutter. The Autel Evo 2 with RTK module obtained survey grade results and lacked a mechanical shutter.
Also the wording from DJI on mapping with both leaves me scratching my head, "DJI Matrice 4E supports precise mapping after enabling RTK function. Equipping DJI Matrice 4T with the RTK module can’t guarantee the final precision."
It says equipping the 4T with an RTK module even though it is permanently affixed.
I just checked, the M4T's camera is not calibrated as Agisoft does not prepopulate the camera calibration, while the M4E does. But when I ran my tests, I did not use this information. I am rerunning the M4E at 15mph nadir with Altitude Opt using the precalibration for the camera to see what it does.
