Making your own ground control points

[Andrex]

Who has made their own Ground Control Points (GCPs)?

I'm going to set up a number of GCPs at a site where I will be carrying out regular drone surveys (it's a developing quarry site, for info).

The GCPs will be picked up by the quarry surveyor using accurate equipment.

I'm thinking of popping along to the local B&Q hardware store and purchasing some thing sheets of plywood, white and black paint, and making GCPs approximately 40-50 cm wide with a large white/black painted cross on which will be pegged to the ground at various secure locations around site.

Just wondered if anyone else has experience in making their own GCPs?

 

[A.O.]

What are they, and what are they for??? Sorry, new flier here..

 

[Andrex]

What are they, and what are they for??? Sorry, new flier here..

For creating an orthophoto or DEM. The built in Mavic 2 GPs is not accurate enough. Manually surveying the GCPs to exact ordnance datum (so, x,y,z) means the generated orthophoto from the software can be accurately corrected to national grid, to a much higher, centimeter, degree of accuracy.

 

[MrHawkeye]

I've spoken with guys that have used kitchen tiles on boards similar to what you're talking about putting together, provided that you can ensure they won't move and the point you're tagging in your photos is representative of the location/elevation you've tagged you should be fine. It doesn't need to be a specific tile or target.

I've had a good deal of success even just using spray paint and 12" nails. I just make sure to take a ground shot so that A) my phone makes a geotag I can refer back to if I need and B) I have something visual to refer back to if my aerial photos aren't as clear as I would've liked.

 

[joecnc2006]

If you are repeating the mission to show progress or removal of material over time I would install permanent control points which can be tagged in every flight over time. Processed and on the correct datum they require. Of course you will need to place CGP's in areas which change over time but you will have a correct base station and permanent control points to come from.

 

[Spartan Drones]

Just a question, how do you know where to place your GCP's ? Do you have to find your location with lat/long numbers and place them or do you just place them? If you just place them, how do you calibrate them?

 

[adam57]

Who has made their own Ground Control Points (GCPs)?

I'm going to set up a number of GCPs at a site where I will be carrying out regular drone surveys (it's a developing quarry site, for info).

The GCPs will be picked up by the quarry surveyor using accurate equipment.

I'm thinking of popping along to the local B&Q hardware store and purchasing some thing sheets of plywood, white and black paint, and making GCPs approximately 40-50 cm wide with a large white/black painted cross on which will be pegged to the ground at various secure locations around site.

Just wondered if anyone else has experience in making their own GCPs?

If you’ve got access to a quarry surveyor with proper GNSS gear, you’re already ahead of the game. Making your own GCPs absolutely works I’ve done something similar for aerial mapping GCPs on active construction and mining sites, and the results were solid.
Plywood + high-contrast paint is a good start, but a couple of tips from experience:

• Go for weather-resistant board if you can regular plywood can warp fast in wet conditions.
• Seal the edges with exterior varnish so they survive more than a few survey cycles.
• Make the center marking bold and crisp; the clearer it is in the drone imagery, the smoother your processing will be.
• If the site is very dusty (quarries usually are), matte paint works better than glossy less glare in bright sun.
• Peg them well or add some weight underneath; wind and machinery movement can shift them easily.

Once painted and secured, they work just fine. Just make sure they remain visible as the site evolves sometimes a bit of dusting or repainting is needed between flights.

If you ever decide to switch to premade, durable targets later on, it’ll save some maintenance but DIY is perfectly valid, especially for long-term static points.

 

[Felix le Chat]

Who has made their own Ground Control Points (GCPs)?

I'm going to set up a number of GCPs at a site where I will be carrying out regular drone surveys (it's a developing quarry site, for info).

The GCPs will be picked up by the quarry surveyor using accurate equipment.

I'm thinking of popping along to the local B&Q hardware store and purchasing some thing sheets of plywood, white and black paint, and making GCPs approximately 40-50 cm wide with a large white/black painted cross on which will be pegged to the ground at various secure locations around site.

Just wondered if anyone else has experience in making their own GCPs?

Save the attempt to earn the Blue Peter badge - off the shelf is available. Been using these as GCP's for over 5 years now. Relatively light, portable, wipe-clean and virtually indestructible. They also stay where they're put.

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