Advice on GCP's for corridor mapping

Hi all,

I need to do some documentation (for potential insurance claims in the future) for a local landowner, before a pipeline is dug down on his land.

Wonder who have some advice on placement of GCP’s on almost mature fields (grain, rapeseed, so fairly tall crops)?

The solution needs to be as gentle on the crops as possible?

I am thinking collapsible tables with a GCP clamped to it, but that is a very heavy and costly solution, which doesn’t go well with having to place them where a car not necessarily can go.

Ideas, that are cheap, sturdy, lightweight and fast to deploy?


If you cannot clear the ground area of grass, maybe drive some tall stakes with specialty made mounts for GCPs? Or maybe a cable attached through GCP via hole, washer with weight at bottom? (Edit: depending on how lush the grass is, hopefully thick enough to support the GCP, may need more than one anchor point to prevent GCP movement due to wind, earthquakes, wild boars, monkeys, crocodiles, or even raptors :lizard:) Is elevation not important? Seems you would have an elevation offset.


So you need to make a portable fencepost with a GCP on top?

What about using a broom handle / small post / piece of lumber? Attach a square of plywood or hardboard to the top. Or if your GCP is solid enough, just screw it to the post.

For stability just use three pieces of string as guy wires. If the crops are sturdy, then tie to the base of the plant. If not, then use tent pegs. If the soil is loose then get the spiral anchors that look like corkscrews or just bring a hammer and some wooden stakes.


You are bringing back memories…
(that are somewhat relevant)

FYI: The linked post below was prior to Reach RS2, Reach M+, Reach RS+, and Reach RS. It was back in the olden days when there was only the Reach RTK kit (small modules) and only one flavour of ice cream and the pictures were all taken in black and white.

…well OK, maybe not that long ago :slight_smile: but it seems like it.


I use a 3ft x 1in garden stake with an orange Home Depot or blue Lowe’s 5-gallon bucket lid nailed on top. The vegetation is taller than that then you have to get creative, but you get the idea.


Depending on what part of the world you’re in, you could always have about 6 locals all the same height hold it on the top of their head like a hat for a beer each? :cowboy_hat_face: Tell them if they move it explodes. :bomb:
People will do ANYTHING for a beer.


Nice. Or maybe two…


… And if you mean an actual linear corridor then make sure to stagger your ground control points from one side to the other so that it triangulates across.



Very rare, but seen

We try to block them coming into the country from Germany with a useless fence :smiley:

Not doing this mapping in the Zoo :smiley:

Maybe one got let loose ?!

Oh yeah, we got those! “Clever girl!”


Basically, yeah!
Something that is man-haulable, easy to install, and easy to remove, but sturdy enough to withstand wind, and the weight of an RS2.

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I think that could be a solution.
I see that the usual DIY stores have fence-posts in 10mm x 1500 mm. That should do that trick… I am not expecting crops over 110 cm.

1500 mm might be a bit of a hassle to get into the ground at first, but should be doable.

Six locals would ruin me in a few hours!
And if i tell them it will explode, my mapping porject would probably be spiced up with the blessed presence of army EOD :stuck_out_tongue:


Nice tip!
So, if I understand your correctly, then zigzag GCP north/south if the corridor goes east/west?


Maybe just implement folding legs on the bottom of the GCP. Or just find a smaller, lighter weight card table and paint the marker on top.

Well, yeah, problem is who do you easily carry 8-10 of those in the tractor-tracks in high crops ? :wink:

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You got it. If not using PPK then you probably want to do 2 just across from each other spaced down the corridor, but with PPK you don’t need that many and zigzag works just fine.

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It might just be the “work” involved since you cannot clear an area for each typical GCP?

Have to keep brainstorming.

How dense and tall are these crops?

Sadly no PPK (if you mean from the drone? ) but this is first time for me where it would make sense.

The corridor where the digging/construction will happen is 35 m x 3 km. 35 meters sounds of too little distance, so thinking 50 meters, and then 150 meters spacing lengthwise… too little, too much?

Either of those should be fine. I usually try to keep my GCP’s within about 170m (500-600ft) or so of each other.


Bought a few different poles to test out in the crops today.

A 20 mm x 1500 mm pole was the over all winner.

  • large diameter tube made is less prone to flexing both in the ground and in the material.
  • lighter weight than a solid 12 mm diameter steel rod
  • more real-estate to mount the GCP on on top.
  • 1500 mm is needed for ready-to-harvest rapeseed. Roughly 30 cm can go into the ground before it starts touching the top of the crops.

Getting the required GCP’s into the field is gonna be a nightmare though! walking isn’t an option, way too many combined kilometers in a day. Will ask the farmer if he can help us, as no ordinary vehicle can span the tractor-tracks.