The role of GPS in surveying

My firm does almost nothing with a total station. A few minor surveying tasks are still best done with total stations, but for us they are limited to tight layout such as a building or flat curb/sewer jobs.

We were doing a topo for a PUD last week and I went over what was needed with the Party Chief. I mentioned leaving control points as we usually do and then setting up the Robot for checks on the control, or I would meet him out there to level through them.

He rolled his eyes and said the last dozen he had done, he sets up the Robot and checks .02' (0.006m) or less on the control. Our GPS has gotten so accurate that it's a warm and fuzzy exercise. He was telling without saying it not to bother showing up. My warning to you would be that I don't survey in heavy canopy, but there is major improvement with that from the old GPS days.?ÿ

@mightymoe I would still like to have conventional checks done.?ÿ All it takes is one bad GPS location to cause havoc.?ÿ I like having confidence in the work I put out.

@va-ls-2867?ÿ

I agree, we still do it, yet it seems more for CYA reasons than anything else, someday we may find a glitch, but it's been a long, long time since there's been one on control layout.?ÿ

Posted by: @mightymoe

My warning to you would be that I don't survey in heavy canopy, but there is major improvement with that from the old GPS days.?ÿ

I do survey in heavy canopy.?ÿ
Nobody does that like Javad can!

(yours truly)

Nate

If you intend to use GNSS equipment only to get on coordinate systems, thatƒ??s a waste of a purchase unless youƒ??ll be buying 20 year old units. With the Trimble R12i you can do everything.

You can get units these days which are sufficient to put you on the grid for less than a few thousand dollars, pounds, euros, whatever.?ÿ

The iGage CHC OPUS X90 has been the best. It doesn't do RTK so there is none of that instant gratification. I just issued mine to my new party chief for his extracurricular efforts and he is keeping it charged and deploying it every chance he gets and learning how to submit to OPUS for his learning projects. I have been using OPUS tied with trig leveling and resections in least squares for so long that RTK is some other universe people talk about.

Thanks for the replies guys

On a lot of the jobs I do I scan the building, so I like to put in control with a total station which is then used to verify the scan data. Also I typically have to measure a load of building roof heights, something I do with my robot too.

So I imagine I'll have a robot on site most of the time.

Which GNSS systems would be good for "getting me on the grid"?

Best regards, Fobos8

I've been considering investing in my own GPS gear, primarily to transform my surveys onto out national grid, but I'm wondering if people are using GPS for other things these days besides transformations.

The role is the same but the advantage of it is it saves you time.?ÿ Less tearing down and setting up to get around obstructions, and being able to reach miles without traversing.?ÿ It used to be that doing a topo could be a little quicker with a total station since the rover needed to be leveled up and then to sit on the point a few seconds, but I think the IMU tech in the newer receivers closed that gap a bit.?ÿ Unless the vast majority of your projects are in smaller, open spaces I think you'd see a noticeable time saving with GPS.

@fobos8

Given you are UK based I'll assume you are looking a rover unit + data collector (if you don't already have one you can use) and will get a subscription to one of the network RTK services (think Lecia, Trimble and Topcon all run services in UK).

Lecia/Trimble are top of the pile and then there are the new wave of Chinese receivers. Also need to consider if you want the base model or top one with IMU tilt functionality. You don't say what total station you have but of it was me I'd want the same brand of GNSS so you just use one data collector with both. With all the ex hire gear in UK could look at a basic model to wet your feet with a view to upgrade in a couple years if it proves to be as useful as most on here expect it will be for you?

Sounds like you don't have a great deal of experience with GNSS so a good dealer that will support you getting started will be the most important criteria when shopping otherwise you will spent untold chargible hours trying to work stuff out, adds up much faster than you may budget for.

Check out https://www.rics.org/uk/upholding-professional-standards/sector-standards/land/guidelines-for-the-use-of-gnss-in-land-surveying-and-mapping/ for some basic info on operation

?ÿ

@va-ls-2867?ÿ

If something does go wrong, and the fingers pointing requires showing that itƒ??s not your fault, yeah conventional checks is piece of mind. Misplaced Concrete is always an argument of whoƒ??s at fault.?ÿ

@fobos8,

As many have stated, there are advantages to jumping to GNSS units that can do all (or almost all) your work.?ÿ But your stated interest is in getting your conventional projects onto a national coordinate system.?ÿ And it sounds like you're interested in moving toward GNSS but not looking to jump in with both feet.

So I would follow the advice of @norman-oklahoma and @half-bubble and go with something that gets you strong data for much less expense.?ÿ I also recommend the iGage x90 OPUS - but I believe it has been replaced by newer hardware (with more capability!)?ÿ The good news is you can still get one for a price in the quite-low four-figures (US$) that covers everything but the tripod/pole to hold it - no data collector needed, includes simple download software. ?ÿ (Look for "static GNSS" at the top of their home page.)?ÿ But I do not know whether there is a processing service like OPUS for the UK.?ÿ I am quite sure, though, that the owner at iGage (also a surveyor, as I recall) would be happy to help you with how to process your data and get coordinates.

Thanks guys for all your input, it's very much appreciated

Question for the GNSS only crowd--how do you tie in 2-storey buildings in an inner city lot infill??ÿ 2 nails with tapes between them and to the corner? Then reduced in a LSA? Or do you use the photo measurements ala Javaf/Leica/Geomax/etc?

?ÿ

We still shoot RTS for buildings and GNSS redundancy when nearby, but I'm intrigued by what others do.