Ground Control Points (GCPs) for aerial photography

Hi guys,

We would like to share with you very simple find we did during our operations. Making reusable Ground Control Points (GCPs) for aerial photography and photogrammetry.

We spend a lot of time testing and tuning our Universal Ground Control Software U[g]CS in a real world scenarios.

For aerial photography and photogrammetry you can rely on modern software like Pix4D, Acute 3D and other to produce good results without ground control points. If good is not enough and accurate 3D model or digital map needs to be rendered you always need GCPs.

We started from “classic” crosses made from painted plates of cardboard, wood and plastic, but they proved not to be practical in every situation and all weather conditions we encountered.

And finally we found that best material for small GCPs is simple ceramic tiles:

For each GCP you need 2 black and 2 white tiles with mat surface. Glossy has reflections and does not work well.

They are absolutely water (rain/snow), wind and mud resistant. Can be easily transported in car and reused almost forever. Until human error takes its toll and you drop them on rocks or hit hard against a car.

Tiles with 40X40 cm size proved good for making shots from up to 100 meters.

This is a shot taken from approx. 50 meter altitude with GoPro:

Zoomed in part of the frame above:

Good luck and safe flights,

UgCS team

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Comments

Alexey Dobrovolskiy February 9, 2015 at 5:49am

And important point - we used only automatic mode and planned routes in UgCS (of course :-). In manual mode there is a lot of chaotic movements and it seems that for software too hard merge separate pictures.

Now we are working on macros for Excel which will produce flight plan for electricity lines reconstruction/diagnostics based on tower coordinates and types. We will publish it here. Our macros will produce flight plan in UgCS format, but it will be possible to modify it for any planning software.
Daniel Perez February 9, 2015 at 5:39am

thats an excellent result using a GoPro I will try with mine, I use photoscan for processing
Alexey Dobrovolskiy February 9, 2015 at 5:28am

We used overlap about 90%, altitude was about 10-15 meters above towers. On up to 100 kV lines it's safe. Camera GoPro 3.

And for processing we used Pix4D Discovery.

What software do you use?
Daniel Perez February 9, 2015 at 4:24am

Hi Alexey,

please find attached the image.

I used a canon s100 with intervalometer, 75% overlap and sidelap, altitude 90m.
Alexey Dobrovolskiy February 9, 2015 at 12:08am
Hi Daniel, I can't see your photo.

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Daniel Perez February 5, 2015 at 6:29am

How did you get the electric towers so clear and nice I always get this result on structures like this.
transient February 3, 2015 at 10:24am

Sport Court interlocking plastic tiles may also be useful for fiducials..

https://www.rubberflooringinc.com/garage/sport-xl-grid-loc-tiles.html
Martin Poller February 3, 2015 at 10:10am

+1 with Garry, what an ingenious solution, robust with a very accurate definition of the cross hair for precise positioning. I'm off to source some black and white tiles on ebay, now where's my tile cement!
Rob Dunbar February 2, 2015 at 8:22pm

I've been using two wood lath in an x shape. I place the lath on the ground and overspray fluorescent orange paint. Works well if you need to come back as the overspray is still on the ground.
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Gary Mortimer February 2, 2015 at 7:55pm

Now that's clever Janis I like very much! Eating lots of pizza and painting the boxes also works for me ;-)

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