RTK Vertical Accuracy

A few years back I attended a demo for machine control. The 'trainer' was going through the steps to set up a job. At the end of his 2 minutes on localization he showed the parameters for a job they were setting up. The scale was several times what it should have been and the slope north and east made just over a 2% tilt.
The saddest part of the whole thing was the discussion with the Surveyors at break. They didn't see an issue. Yes, equipment in the wrong hands is a bad thing...

Actually, under open skies, the GNSS systems of today are pretty reliable horizontally and vertically. I trust them to yield results within specs (1 cm / 2 cm's) if proper methods are used.

> Actually, under open skies, the GNSS systems of today are pretty reliable horizontally and vertically. I trust them to yield results within specs (1 cm / 2 cm's) if proper methods are used.

I do, too, with the understanding that the spec is 1-sigma and has an additional 1 ppm error component not mentioned above. Vertical errors of 4 or 5 cm on a 5 km vector aren't uncommon.

> I do, too, with the understanding that the spec is 1-sigma and has an additional 1 ppm error component not mentioned above. Vertical errors of 4 or 5 cm on a 5 km vector aren't uncommon.

I am a construction guy, I work with short baselines, usually maximum 1 km. My experience is the vast majority of QC check shots under an open sky are within mentioned numbers above.

Drones for photogrammetry?? I thought that commercial use of drones was illegal in the US?? did I miss something?

Field tile to the nearest 0.1'? They may "think" they need that kind of accuracy, but unless the field is flat as a pancake, I doubt it. just like they may "think" they are getting that kind of accuracy from their gps and measure up tractor methods.
The fact is, a good field guy can lay tile and make it work by eye. At least that's how I always saw it done growing up.

water flows downhill.

We have Sections with a foot of fall in a mile. Eyeball that and you will have a problem...

> We have Sections with a foot of fall in a mile. Eyeball that and you will have a problem...

for sure!! wow. and I thought Illinois was flat!

Andy is in Florida: also known as the flattest piece of delineiated land on the planet.

Keep in mind what is being measured. Yes they MIGHT be getting the nearest 0.10' but I bet they don't know, but if you are taking shots on plowed farm ground, its so rough the nearest 1' is all your really getting.

> Keep in mind what is being measured. Yes they MIGHT be getting the nearest 0.10' but I bet they don't know, but if you are taking shots on plowed farm ground, its so rough the nearest 1' is all your really getting.

exactly right, David.. the whole thing is just silly.

I use a Leica GS15 with a base and also with a network. All I know is that when it needs to be accurate, I get out a level and shoot the elevations.

Yes, I get out the level a lot. Must agree with that, but for a field survey, there is nothing that will compete with GPS and a four wheeler. Either do them RTK or post-processed. Much better than lidar surveys I've used, some of those were good, some were bad but none were nearly as accurate as GPS and a four wheeler. You can do them with a total station or robot, but for a much higher cost and little benefit. And if you try to cross-section and level them you miss too much.

I expect what they are doing is the original ground topo with the tractor or atv. They then design their tile runs based on that. The tiling machine would be a slow movimg tractor with better accuracy to better control the depth. It would probably be a minimum of 3 ft deep, and a minimum of 4" tile, so there is some wiggle room there. All it has to do is not have any spots in it high enough to keep it from flowing. The accuracies they are getting may not be what they think, but evidently the method does work.

Yeah, that's what I was trying to say... Not as well as you did, though.
They can believe it's .001' accuracy too, as long as the water flows, who cares.

Ps. Finally replacing old #49 with a new S6!

What year did you buy it? Did it quit or you just upgrading?

Still working with the geo every day. Traded in an older Topcon I had on the shelf.
Haven't had an afternoon to really even work with the S6 yet, between the weather and finishing projects.