Hey everyone! PE and SI here. More experience with the PE end of things, but learning the surveying part as I go. Work for a local gov't headed by a PE/PS (boss is the only PS in the office). We are not an area that requires any survey to be tied to the state plane. We have a Trimble R12, TSC3, and access to the state DOT's excellent CORS system.
Boss wants to use the R12 on all our road centerline monuments and put together an online public coordinate dataset. From everyone involved I'm hearing talk of single, 1-3 minute occupations per monument. No revisiting at different times, or on different days. The goal is apparently to put the data out there "because it would be good for people to use."
When I asked if we wanted to start building a control network (our area's is sparse), one of the involved said we don't need control points anymore since we have GPS. About multiple observations, the boss said we can't let perfect be the enemy of good. (And, as I was told, the local PS's will still need to occupy the centerline monuments anyway and if there's a difference in coordinates, they can report it on the plat). NOS NGS 92 be darned, I guess.
I feel like I have a decent (though still learning) grasp of the benefits and limitations of GPS. But after what I heard today, I feel like everyone at my place views GPS as a magic 8 ball.
Am I wrong to have a bad feeling about this whole thing? Anyone have good arguments, either to convince me - or I can use with the folks I work with?
Lots to unpack there.
I'm not against collecting the data.
I personally would love to have that database.
I don't know your situation with respect to control, but in three minutes it's simple enough to gather multiple locations of points that can be adjusted. Going back hours or days later is an anachronism from years gone by. It's possible to gain different satellite configurations by simply turning off and on different ones. if that's a concern, I wouldn't worry about it. My assumption is that safely accessing the points in the middle of the road is more time consuming than the actual collecting of data so use the few minutes at the point to get two sets of data and adjust to multiple CORS points, locate, refix, locate.
For DOT projects control points should always be set.
Time is one function of GPS control networks that can't be overlooked. Set control and as the project progresses, that control needs to be respected. I've seen times where GPS jockeys try to override control from 15 years prior that all location, design, takings, ect were based on and because it was just too hard for the surveyor to push a second button on his DC they insist that the whole project be shifted to accommodate their inability to actually survey. It's really a stain on the profession. Project control will mitigate that issue. Moving into 2022 or 2030 or whenever or whatever the "new" control is called and is released will highlight that issue even more.
I don't understand what the goal is. Are you building a GIS where this data will be displayed?
So you put coordinates on centerline street monumentation. What is the purpose? Either you are going to use those coordinates to replace any monuments that are destroyed or you are going to publish those coordinates to be used as part of a control network for the area. Help me out if anyone can suggest another use of this endeavor. If you are not intending to do one of those things, it seems to be a waste of time and effort.
The centerline monuments tied will be the control monuments of the survey. Their values, if tied as proposed, while not "survey grade" will be a major improvement on the GIS derived values your planners are likely currently relying upon. So I see value in what is proposed.
they insist that the whole project be shifted to accommodate their inability to actually survey
AMEN !
Thanks for the comments so far!
The goal would be (as far as I know) to add a monument layer to the current GIS map. Click a monument, up pops all the details. I actually don't think there's anything wrong with that. I wish we had more data like this out there.
My misgiving is that the staff involved tend to view GPS as the be-all, end-all for data collection. (When hired, the one tech was surprised we still used a TS). Just push a button on the DC, get coordinates, move on. And once these coords go public it'll be impossible to call them back in. If it's out there, it'll get used.
If it were me, I'd take the time at the beginning to make sure the procedure is good, test a small area, check results, before moving on to bigger things. But that's me. 😉
Boss wants to use the R12 on all our road centerline monuments and put together an online public coordinate dataset.
one of the involved said we don't need control points anymore since we have GPS.
Am I wrong to have a bad feeling about this whole thing?
No you are quite right to be concerned - this is mixed up right from the start
Until you can get purpose, benefit and budget this project is doomed to fail
(I also have significant concerns about field technique and crew safety)
Retired years ago and limited experience with GPS. However, have seen many ignore maintenance of basic tools. If rod levels, tribrach levels and optical plum are out of adjustment random errors are induced. Multiple occupations MAY detect some of this. For a project like you describe every part of the equipment should be checked both before and after the project.
There is a safety issue using centerline monuments, no one wants to get run over. You could throw out a few monuments in better locations in my opinion. I personally don’t have a problem with using rtk for this but I’d for sure shoot them twice at different times of the day.
Work for a local gov't headed by a PE/PS (boss is the only PS in the office).
When thinking about starting a project, I like to figure out who it's for and what already exists. When I see "local gov't headed" I think, wow, this municipality has a mayor who is a PE/PS. If that isn't the case (or even if it is) I think a good first step is to see what other organizations in the area are gathering GIS data, and if they are making it public. I'm a town justice of the peace who hears appeals of the value assigned to properties for real estate tax purposes, and a retired PE (computers).
Centerline can't be used as highway control.
Couple thoughts. To have any real weight, the survey would need to be done or under the supervision of, the authority in charge of the highway ROW. In a perfect world this wouldn't be a GIS product but a Record of Survey, signed, sealed and recorded. In this perfect world reference monuments would be set in protected locations that would negate the necessity for anyone to have to occupy any centerline monument. Coordinates would be published along with any relevant metadata that might be useful to surveyors fifty years from now. These things are always just a snapshot in time, but can prove invaluable under unforeseen circumstances and just from a safety and practical manner.
Just because I'm paranoid, doesn't mean they aren't out to get me.
This proposed survey can never be "survey grade" useable by any surveyor because there are no licensed surveyors involved. Because of that fact the OP's boss is correct, actual PLSs will have to make their own measurements when using these monuments. Therefore the effort is, at best, one of providing high quality GIS data. A single visit to each monument fills that bill adequately. Such data is not entirely useless, not even to the future surveyor. A second visit would undoubtably improve the positioning, but it would never make this a control survey.
Surveyors who are working with the CORS system will start using these coordinates in their boundary surveys without even visiting the monument. Imagine if you had state plane coords on the SI's of your block? You could break down the block and go out to set property corners without even doing an initial boundary survey. Not that any of us would do that...
Centerline can't be used as highway control.
What???? Are you trying to say that centerline monuments don't have as much weight as right-of-way monuments? It is a rarity around here for the original survey of a market road to even mention right-of-way width let alone monuments.
If you mean strictly for control, I've worked on many a project where the centerline fell in a median. I have used these quite successfully as control points. Maybe not so much on an undivided road.
Back to the post, unless the centerline monuments are in a protected area, i.e. in a turning lane or median, I usually tie them conventionally. I don't like to hang out in the middle of the road longer than I need to. I can recover it and level a bi-pod with a couple of cones. In about half the time it takes to get one (of two or more) RTK sessions, my MS60 can rap 3 sets from a safe location. I just tie my control network into a geodetic network.
Oregon law allows road centerlines to be referenced to a control network. No more need to set centerline monuments in inaccessible locations.
Personally, I would love to have a dataset like that for internal use, but I wouldn’t be comfortable putting that out to the public on a format that didn’t involve them signing a waiver saying that they understand that this is GIS data that was not certified by a PLS.
edit: I believe that we have similar roles, I work for a municipal PE as well
Oregon law allows road centerlines to be referenced to a control network. No more need to set centerline monuments in inaccessible locations.
That's more similar to surveying in NZ. We are a recording state and show all our traverse/control marks (including ties to national control points) with vectors connected to boundary monuments (or calculated positions if not safe/possible to monument).
Centerline can't be used as highway control.
What???? Are you trying to say that centerline monuments don't have as much weight as right-of-way monuments? It is a rarity around here for the original survey of a market road to even mention right-of-way width let alone monuments.
If you mean strictly for control, I've worked on many a project where the centerline fell in a median. I have used these quite successfully as control points. Maybe not so much on an undivided road.
By highway control, I mean control set for, property location, mapping, design, construction, ect. (I'm inferring the OP meant this). Even on a divided highway it's often not ideal to use the centerline monumentation for control work. Of course, centerline can be used for boundary control. I'm not talking about ROW monuments as control, only points placed randomly and surveyed through with the desired coordinate system for the highway.
Generally, a DOT control point is placed where it's likely to remain through design and construction. I will guess about 40-60% of control points survive the process in rural areas, less in urban projects. In a full reconstruction it's obvious 0% of centerline will survive.
Today control surveying seems less important with GPS, but if there is mapping, takings, design based on a coordinate system and that coordinate system slides over time the fixed physical control points onsite will supersede the numbers from the black box. Plus, there's the issue of elevations that should be leveled (until 2022 shows up). And the mysterious process called machine calibration that should have something onsite to calibrate to.