Thanks for sharing ! I’ve gotta try it !
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Great job, I wanted to try this but have not had the time. So happy that you did! What PRINT MARKER parameters would you recommenced now that you have printed and tested? What would change and why? Any and all feedback would be greatly appreciated by the community and myself.
Marker type:
Center point radius,mm:
Targets per page: is a no brainer
Font size:
the center point radius doesn’t really matter, as long as the targets fills up a page.
The size can be adjusted in i.e. Photoshop afterwards.
My targets are 28 cm (from edge to edge), and works perfectly with the P4P at 27 meters (0.74 cm/px).
I also did test 50 meters, where the auto-detection did not work (I have not done tests in between). There is also a difference in the required auto-detection threshold value having the targets in the center of the frame vs at the edge of the frame (50 vs 90 respectively).
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Detection Markers parameters were the default setts? wizprod
Tolerance: 50
Nop, as mentioned above, tried with different settings.
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I’m starting to carry these with me in more urban environments. I bring both white (asphalt) and black utility tape (concrete/sidewalks). Comes in about a 2" strip. Cheap!
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Nice idea !
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We do this quite a bit on as-built surveys where we don’t want to leave any permanent markings. Only problems I run into are that the area must be clean and dry (which is why I carry a small coarse broom) and the reflective nature of the tape doesn’t do well when the sun is up high.
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So, having worked with my Coded targets for a year now, here are some learnings:
Pros:
- Looks really pro on site
- Easy marker-recognition in Metashape
- Durable
Cons:
- Heavy as the marker size compared to other markers need to fairly large
- Hard to manually set marker in center if at higher GSD than designed for or, more commenly, if the target is at the blurry edge of the picture frame.
- Takes too long to make compared with the gains
- Can carry a maximum of 10 at the time when walking with the rover.
- Auto-recognition very sensitive to shadows from tree or tall grass. This would actually be the biggest con, because it removes much of the incentive of doing these in the first place.
So, now I have gone to 30x30 cm vinyl chess-tiling, this works nicely even up to 3 cm/px GSD, cheap and I can carry 20 at a time, before it becomes too heavy. Of course I have to manually mark these, well, one more reason to buy a M2 PPK solution!
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When I set up my old companies Drone-Survey outfit, I used rubber water heater pans that I spray painted and drilled a hole through the center!! I love your approach too!
Do you have a picture of it, or something similar? Sounds quite creative, but have no idea what one would look like!
I ordered some plastic garage floor tiles and they’ve worked quite well. I use four (black and white). But you can also make a larger target if you needed to be flying particularly high.
Very durable, very light and it’s nice that you can dismantle them if you want to pack them away.
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Nice. I used orange and blue which has been a good contrasting color combination across all construction site surface.
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Sure, they were these bad boys:
https://www.homedepot.com/p/Everbilt-24-in-Plastic-Drain-Pan-15021/205681003
I just spray painted them. They have to be durable and replaceable by nature of having water heaters sit on them for years, but they are only about 10 bucks. you can also take a small hook to collect them through the drain pan hole when collecting after setting out the targets.
sorry for the delay in response.
I tried something similar, IKEA’s “Kalas” plastic children plate (Produkter - søg efter produkter. Få et komplet overblik her - IKEA)
I drilled a whole through center for a nail, and then a 5 cm (2px at my my usual GSD) spray-painted center.
I use them twice for with around 50 deployed plates, both times I really wasn’t happy with the marker placement accuracy. It was especially hard to place the markers correctly at steep angles and in the corners of the frame, as you really couldn’t clearly make out the center very well.
On top of that, the edges of the plate throws off precision even more, probably ±2 cm when the edges are 1.5 cm high.
Only upside was that they were really easy to carry, and you could carry 50-60 at one time.
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Nice test. I like that they come in different colors as well. When I use the Home Depot 5-Gallon bucket lids I took one and cut a cross-hairs template on it that I paint when I put them down. Duct tape works as well.
As for steep angles, you’re not putting them on slopes are you? They are better served on tops and toes of the slope as the target gets warped and the centering of it gets tough. The same reason why we don’t use GCP’s on oblique missions.
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Nope, steep angles as in laying on flat ground an being seen by drone camera at a steep angle, i.e. having the camera at 65 degrees and having the target in the upper most corners of the frame. Makes it look like an squished oval. On top of that, lenses are usually less sharp in the cornes, so add a bit of blur into the perspective as well… not pretty! Less problematic with the checker pattern.
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Understood not slopes, but it is what I am talking about with oblique images. I preach the same with outer ring distortion and focus. I is ok for mass shapes, but for finer sub-meter detail I don’t think it does any good for the photogrammetry.
Got it!
In the first test using 50 gcp’s, this was to develop a solid camera calibration, so I really needed to get any GCP’s in the corners included as well.
I always have my focus set to infinity on the P4P, so I have a hard-stop, basically to make sure my calibration has an absolute point-of-reference.
Some of my volume measurement stuff are done at 0,6 cm gsd and thus pretty low altitude, here I really need obligues to be able to characterise the stockpiles in a trustworthy way.
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