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GNSS-Total Station Hybrid Survey?
Trying to figure out how to (If it’s possible) do a boundary survey using a combination of VRS- RTK and a total station. I understand that I could simply bring control in via RTK and then run the gun off of it. But is it possible to run most of the property corners via RTK and then shoot in the 1 or 2 other corners (Under heavy tree cover) with the gun? What would that look like? Do I call it a GNSS survey or is a standard survey? Or is it something altogether different?
Usually the verbage placed on the map reads ” … I certify that this survey was drawn under my supervision from an actual GNSS survy made under my supervision…” So, Would it be a GNSS survey or not? This is what I’m looking at:
The client is asking for a survey for recombination of 2 properties. I have the deeds and previous survey maps for both properties. Both are referenced to Magnetic North (one in 1968 and the other in 1990) 6 of the 8 corners have been confidently recovered except for 1 that was disturbed and one that looks to be washed out by the creek. My plan was to collect all the recovered corners via RTK (as stated above) and then shoot/reset the others in via TS.
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18 Replies
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Is the “GNSS” or “standard” qualifier required before “survey”?
I am used to seeing something like “This map correctly represents a survey made by me or under my direct supervision…”
Then in the notes there is something along the lines of:
“This survey was performed with a [insert model here] total station and [insert model here] survey-grade GNSS receivers using corrections broadcast by [insert RTN name here]. Redundant network RTK and total station observations were evaluated and adjusted simultaneously using least squares analysis.”
(If you had to pick one or the other, I would lean toward GNSS survey, since the TS positions would be derived from GNSS observations.)
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil Postman -
Using GPS for a survey is more about setting up your coordinate system and easily getting on a projection that is tied to an ellipsoid, a worldwide system, the TS is tool similar to the tape measure to get your H.I. Important, but you really don’t need to state that you used it during the survey.
Frankly, stating that the survey is GNSS is kinda surveying virtue signaling and irrelevant to the task of retracement, it’s the basis of bearings and distances, and the metadata that counts.
But I do know of some regulations that required stating the actual brand and model of receiver used in a GPS survey. One of those now very outdated requirements.
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What does the PLS in responsible charge of the work say?
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Time for another Star*Net plug. So easy to combine GPS vectors and total station measurements simultaneously. Other LS packages can do it also.
Also a plug for Low Distortion Projections, which make grid scale distortions small enough to ignore.
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You can do anything with anything. Ask yourself what is the quality of my RTK or VRS?
I have been combining Static GPS with Total Station work for 20 years. Did some RTK and never cared for it, so I never worked hard at it. 10 to 12 static points or even more. If I was tying separate Total Station parts solely with GPS points I always tried to have at least 3 in each traverse segment. Sometimes I used a GPS pair to get started so that my traverse through the woods would be on system as I headed for another traverse segment. At times I worked with other surveyors, 4 L1/L2 (2&2) units and my three L1s or 3 L1/L2s and my 3 plus his 4 L1s. 2 or 3 guys in the field setting up and sometimes moving gets your traverse control nailed down in a few hours and have plenty to check into for 3 and 4 days of trasverse. Always scaled the GPS to ground, too old to learn to do it on the grid. Software has made that much more seamless.
Paul in PA
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stating that the survey is GNSS is kinda surveying virtue signaling and irrelevant
oh I do Love that!
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Frankly, stating that the survey is GNSS is kinda surveying virtue signaling and irrelevant to the task of retracement, it’s the basis of bearings and distances, and the metadata that counts.
Not really virtue signaling. Apparantly in NC (21 NCAC 56 .1607 GLOBAL POSITIONING SYSTEMS SURVEYS) the surveyor has to have verbage to the effect of:
“I, ____________________, certify that this map was drawn under my supervision from an actual GPS survey made
under my supervision and the following information was used to perform the survey:”I already knew this. But this isnt purley a GNSS survey, it’s 75% GNSS with 25% conventional. Eitherway I’ll put both sets of verbage and sign off on it or just call the board and ask. Surely I’m not the only one that has done this.
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There is a tendency to equate surveying using GNSS/GPS with expressing coordinates on a projection grid, such as state plane. And, conversely, surveying with the total station with local coordinates. While GNSS/GPS has made using a grid projection much more practical the terms are not synonymous. You can survey “on the grid” using transit and tape.
Remember that the NAD27 datum was developed entirely without GPS. And the original NAD83 datum had only a token few GPS vectors incorporated.
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I put each certificate needed for each type of work performed. There are several in section .1600 of the board rules.
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One of those regulations I’ve seen elsewhere, I would state that the survey is based on GPS. I would also explain my basis of bearings and distances, coordinate system, SPC if used, scale factor to get to ground, if you state coordinates on the plat then you need more metadata to get there such as a tie to a HARN point and the coordinate used on it or OPUS observation; epoch is important and of course the ellipsoid which would be defined by the SPC.
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This is really a two part discussion. Part one is can a hybrid survey be done. Part two is how to state it.
Part one- yes. By computing where the TS is by observing two or more RTK locations. (resection) There is at least one manufacturer that facilitates this with an RTK receiver atop a rover pole with a TS prism below the receiver. They support a configuration for what they term a hybrid survey. I works quite nicely provided you are ok with RTK type accuracy results and not mcmillimeter results.
Part two – First – someone will need to explain to me why on earth anyone needs to know how you arrive at a certain level of precision or accuracy as long as you certify to it as a professional. Second – if you must – this survey was executed by using both (manufacturer and model) global navigation satellite system and (manufacturer and model) total station equipment specified to exceed the required accuracy.
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Yup. All that is in the rest of the specs … I just didnt want to post the whole thing here.
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He says, “Check the Rules and Laws and call the board with any questions”
I’m the PLS in responsible charge.
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The GNSS certificate should be placed on the map anytime that method is used on the survey, whether it’s setting control or locating boundary monuments. The Boundary certificate is used anytime work is performed on a boundary or easement or maybe something like a lease area. There is also a certificate for Topographic Survey. If I use GNSS on a topo I also put the GNSS certificate. The GNSS certificate doesn’t take the place of the Boundary or Topographic Certificate. It doesn’t report the reference deed or the contour interval for boundary or topo respectively.
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I would not mention that I used the TS, can’t see any harm in it, but the point is that the basis of the survey is GPS. You could make a mess of a plat showing each point as being a TS or GPS point.
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integrated survey doesnt make sense to me. why walk around with extra stuff on your rod when you could simply get all your observations with GPS, then go back and setup the TS to get whatever you missed. you have to set the TS up anyway.
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I use all of the verbage that is listed.
“I, ____________________, certify that this map was drawn under my supervision from an actual GPS survey made
under my supervision and the following information was used to perform the survey:
(1) Class of survey: _____________________________________________________
(2) Positional accuracy: _________________________________________________
(3) Type of GPS field procedure: __________________________________________
(4) Dates of survey: ____________________________________________________
(5) Datum/Epoch: ______________________________________________________
(6) Published/Fixed-control use: ___________________________________________
(7) Geoid model: ______________________________________________________
(8) Combined grid factor(s): ______________________________________________
(9) Units: ___________________________________________________________”I have most of it already completed on my borders so that I only have to fill in the parts that change. I use this even if all I am doing is a grid tie. It’s annoying but it only takes a couple of minutes.
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In my experience it saves a ton of time and is super efficient when running field to finish software. I get more time at each setup, I don’t have to cover ground I have already walked or leave big holes for later with a bunch of unfinished strings. More continuity is better for busy topos.
I can leave the base running all day and just move around my TS. Take off the rover with the quick-release when I don’t need it.
I can flip back and forth between RTK and TS with the push of a button (TS knows where I am because it knows where the rover is), and measure mons or control points with two independent observations at the same time, which is awesome for analysis and adjustment.
The two-point resection is super slick for quick setups that would take far too long to traverse into, or for scanning total station jobs where you won’t have enough overlap for registration.
It can be a bit of a hassle and there are plenty of times when it doesn’t make sense, but I highly recommend giving it a try…
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil Postman
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