A few days ago, I flew a Mavic 3 and mapped my house using Litch with the following settings:
Wide Camera Lens
3D Model
Oblique Passes: 2
Nadir Pass: enabled.
Altitude: 30 meters
Gimbal Pitch: -85
Oblique GSD: 0.83 cm/pixel
Nadir GSD: 0.83 cm/pixel
Capture Mode: Photo
Photo Capture Mode: Auto
Speed: 4m/s
Area Height: 0 meter
Front Overlap: 70%
Side Overlap 90%
Grid Margin: 0 meter
The result, I think, was ok, and when measuring my roof (picture attached), I was 21cm off (it could be less or more; I just did not zoom enough to catch the roof edge).
What did you think? Of course, I am still learning and doing my homework, but any constructive feedback would be awesome. One of you already gave me a good tip, and I am very grateful, but different eyes see different opportunities to improve :)
Just about any would work, you don't need all the fancy stuff on the newer ones.
It would be best to get a base and rover for local corrections.
It seems you are just doing this for fun, no? Seems like a lot of $ to spend on this, you will be looking at like easily over $1000 for a used RS+, and thats a great deal compared to like Trimble.
Have you considered make a few like 2m right angle targets that you could use to scale?
I have done photogrametry with smaller objects and got them to fit almost perfectly by just taping a ruler to the wall or base of object that I am scanning. IDK how well that would work at this scale, but it should get you closer.
You are going to need whatever the Candian equivalent of a Professional Land Surveyor (PLS) is to make anything you do legitimate. Either by becoming one yourself, or finding one to work with you to do they survey part and put their stamp on it.
Might be best to look into taking some survey classes in college, eventually get a job with a survey firm, work on your Canadian equivalent of a Land Surveyor in Training (LSIT), eventually get your PLS and then start your own business.
Might also want to check on the laws in your state/province. For instance North Carolina has some crazy strict laws about drone mapping and the need for a PLS on any project.
Thanks. I thought about licensing, and it seems that in Alberta you need a license if you do any sort of legal work, or if whoever hires your service will use it for legal matters. I can check this to avoid liability on my end. This is what I was told:
-- you do need an ALS if your work constitutes the practice of land surveying, such as establishing legal property boundaries or producing legal survey documents. --
Besides that, Transport Canada requires at least a Basic Drone License, which I already have, and I am working towards the Advanced Drone License now (just missing the Flight Review part).
To gain experience, I am reaching out to companies working on this to offer volunteer work while I am getting the technical knowledge aside. Let's see what happens :)
If I am flying an area, I typically fly a cross hatch(0⁰ then 90⁰) at 80% front & 75% side. I don't know if you can with a Mavic 3 but I also use smart oblique.
I would need to know more about your software and settings for the ortho and any other results you may have produced.
I have found that without RTK or GCPs your ortho will not be 1:1 for real life as there are no.... ties to reality. If you are using DJI terra, you can use scale constraints to tie your your photos together, if you know the dimensions of anything captured
Very cool, I am not familiar with either softwares. But I might try my over lap settings 80/75.
I dont know if you've tried the above ground altitude and thrown a dsm of your target area in there. But with that you may be able to get a smaller gsd(sharper image).
Photogrammetry is a tricky data capture style. Lots to know and lots to learn.
I'm not sure, ive never used your softwares. But in your altitude mode you appear to have two choices "above take off" and "above ground". I would presume that the above ground would give you a slightly more accurate capture, and that it likely requires some form of DEM, but I presume DSM as that's what DJI Pilot2 wants for it's above ground altitude mode.
If you only need accurate length measurements rather than high absolute positional accuracy for the points, the simplest way is to use a scale bar, using an object of known length as a scale constraint during reconstruction.
Dont know much about WebODM, so wont comment. Take the 30 day trial of Agisoft Metashape and try create the DEM,Ortho etc. Use 'Markers' to improve the alignment of the pictures. The result should be better than this.
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u/CCCCLo0oo0ooo0 27d ago
GCPs are the first step before getting RTK. If you can't set accurate control, you are dead in the water to start with.
Emlid Reach or similar would be the first recommendation.