We've been using 4 white painted 4' lath arranged in a "+" around a spike, oriented more or less cardinally. Good visibility in the imagery, easy to carry in a lath bag. Also have some homemade targets made from 4 street name sign blanks, large hole drilled near one end and connected with a pivot made from pipe fittings which allows them to be fanned out for target use and folded together for carrying.
Not reuseable, but cheap enough to be expendable. I recently set out targets that were 2.5" x 4" red and white stickers. The kind I've seen used for years, but I can't find a picture on line anywhere. I bought mine at Portland Precision Instruments. They are made by "Duramark Survey Products".?ÿ The targets were perfectly visible in the aerial photos. And would have been at half the size.
Once upon a time I had my business cards printed with the red/white checker pattern on the back. In those days I was stapling them to lath for backsite targets. When I get into drone flying myself I'll probably do that again.
I've seen plastic cards of similar size with the red/white target on them designed to be hung on plumb bob strings. They would probably work great for reuseable aerial targets.?ÿ
I made a bunch of these.?ÿ Cut a couple sheets of hardboard into 2'x2' squares.?ÿ The black and white is that sticky-back drawer liner vinyl stuff for your kitchen cabinets.?ÿ They work pretty good.?ÿ Otherwise we just paint 6" dots with a Mag nail in the center for hard surface and parking lots.?ÿ
I made several from masonite and tiles. Tracking time, cost and results we paint nearly all of them now. Alternating squares of white and flo blue with a nail in the center. Point number at top right, read from the south.
I made a bunch of these.?ÿ Cut a couple sheets of hardboard into 2'x2' squares.?ÿ The black and white is that sticky-back drawer liner vinyl stuff for your kitchen cabinets.?ÿ They work pretty good.?ÿ Otherwise we just paint 6" dots with a Mag nail in the center for hard surface and parking lots.?ÿ
That's a very good idea. We may use paint in parking lots or pavement, but our first project is on a soil site so a hard target is needed. I went to harbor freight and bought the 25"x25" foam mats, will use your idea for the white squares as the mats are already black. They are lite also.
I have done a ton of Photo ID points for photogrammetry projects, just the first time where a drone was required.
I assume resolution is such you'd easily see 100 mm at flying height of drone. Form triangle of three if need greater area.?ÿ
?ÿI've also used two white metal guide posts (flat ones about 1 metre long) in form of an X with a hole drilled in centre and a ?«" piece of reo (deformed bar) driven through to hold them down. These do an excellent job.?ÿ
I have just completed a job where, on the recommendation of the photogrammetry guys, I made some 600*600 (that's around 2ft for the metric impaired) squares of corflute.
Corflute is cheap, light, easy to cut and will last months outside. It is often used for signs for real estate agents etc...
Run strips of heavy duty duct tape across the diagonals and you have a target that can be nailed down where needed.
I have just completed a job where, on the recommendation of the photogrammetry guys, I made some 600*600 (that's around 2ft for the metric impaired) squares of corflute.
Corflute is cheap, light, easy to cut and will last months outside. It is often used for signs for real estate agents etc...
Run strips of heavy duty duct tape across the diagonals and you have a target that can be nailed down where needed.
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That looks like what is sold as "FRP" here in the states. FRP stands for Fiberglass Reinforced Plastic.
Corflute is thin plastic both sides of a sort of 'corrugated cardboard' infill all sandwiched together. It's all plastic, no cardboard. Wouldn't survive on a wall inside. Slightest ding and you'd have a hole in it.
I've used that for targets for aerial photography done at higher (plane) altitudes, not drone photography.
It's excellent. No need to buy here, just scrounge from Estate Agents. Or go for a walk and 'borrow' a few off fences etc?ÿ ??ÿ
Corflute, or equivalent, can be made to last for years - we laminate two squares together, with the flutes at right angles and it is very rigid and damage resistant. Cross as the Jim Cox method. edge seal with clear tape. If you place a peg and then screw the board down (with a protecting washer) if the board does get destroyed it can easily be replaced in the same spot. Equally easy to recover board if it hasn't got to stay in place.
We use 16 inch square, so as to get 9 completed boards out of a 8x4 sheet.
I've always used 3'x3' vinyl targets. They work great, I havent had a chance to try them yet but I can get the Propeller GPS embedded targets which look pretty awesome, although a bit costly.
I'd be interested to know how users have found the Propeller system to work. The system seems to be based on the theory of getting a decent result from a number of less accurate observation sets. While this probably works most of the time, what happens when the geometry is poor? I also wonder about how good the sky view is when these boards are sat on the ground (unless you are out in the desert). This surely limits their use on some sites - a system is only useful if you KNOW it will work before you arrive on site.
I just purchased these?ÿ24"x36"?ÿendura-cor plastic sheets.?ÿ I plan to cut them into 8" widths and put them in a "+" shape with a nail & washer in the middle.?ÿ I will need to remove them once the aerial work is done.?ÿ Hopefully I can reuse them on another job.
