I'm currently surveying a long ROW. Along the ROW are fresh established control points. 3" caps imbedded in concrete posts. These were static surveyed then leveled through using a set of first order bench marks and a HARN point/Benchmark.?ÿ
One task is to check all the control points while doing the more important work.
Of course having 41 control points is a luxury and they all check really well to my RTK survey. While occupying I collected a static session and sent it to be processed by Trimble. It was 0.03' vertically. 0.03'!!!!
I was taken a bit aback, didn't think it would be that good.
Geoid 18 is the bomb!!!!
This site is a long way from any CORS stations.?ÿ
Don't take this wrong but welcome to the 21st century. We've been enjoying similar results for some time. Even with 12B. Just curious about the spacing of those marks.?ÿ
The control point spacing or the bench mark spacing?
The control points are <1500' and intervisible so the spacing varies. Bench marks; the NGS shows 11 of them over 8 miles, no idea how many have survived.
There isn't a CORS site within 50 miles.?ÿ
We don't get these types of results, ever.?ÿ
Normally, if I roll my own I will approach 2cm's, OPUS 3cm's and a bit better with Trimble's processor than OPUS.?ÿ
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We evolved to 3d control and increased spacing. We could no longer justify having benchmarks separate from horizontal control with respect to primary project control. During construction, control can be densified as needed on a temporary basis.?ÿ
3d control?
Not sure what you mean by 3d control, I haven't used another type.
If you mean GPS verticals only that will become standard here in 2050 when the 2022 NGS is released.?ÿ
I would assume during construction the 41 points effectively become about a dozen, close to bridge points and a few others for machine control. However, we are seeing a need to densify control for fine work using machines controlled by RTS and not GPS.
Watching a hands free curb and gutter machine controlled by a robot is a revelation. But you need way more control than a typical base/rover set-up.
I will guess that there will be almost no survey stakes set. Maybe for some fencing and bridges.?ÿ
All I meant was vertical and horizontal control are the same geodetic survey style monument with project xyz published. We actually quit using the word benchmark.?ÿ
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You are right about the need to densify for machine control. The contractor's surveyor does that at the time it's needed. I'd much rather do secondary control survey as opposed to staking hubs.?ÿ
I got ya. The benchmarks I'm referring to are a series of benchmarks set in the 1950's,,,,, I think.
The control sheets sent to me don't even show them, I didn't see any of them besides one I happened to walk by.
The project control is all static adjusted GPS with a level run tied to the first order benchmarks.?ÿ
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The control sheets sent to me don't even show them, I didn't see any of them besides one I happened to walk by.
I hated it when that happened. We were in charge of making those sheets and we always included the NGS control used and project LDP. Or at least that was our intention. We didn't put the plans together or seal them though.?ÿ
Oh no, all's cool, this was a rush job. I had to push back the due date cause the control wasn't finished, so once they got that to me it's all hands on. The control sheet is as good as it gets, it lists all the CORS points used, the lat, longs for each point, state plane in meters, usft, and the surface coordinates, Ellipsiod heights, geoid separation and ortho elevations in meters and us feet. it also lists the type of processing used and a bunch of other useful info. But there isn't a list of bench marks save one that's the HARN point.?ÿ
I infer from you comment expressing uncertainty as to when the BM heights were determined. Excuse me, if I misunderstand your comment.
It is actually very easy to find comprehensive information about any BMs in the NGS DB Including the actual field observations and distances.
If you have the point??s PID start here:
?ÿ https://beta.ngs.noaa.gov/datasheets/leveling-projects/index.html
You can find the level projects (and other types of projects) associated with a PID via a link on this page. You enter the project identifier or the PID in the entry box. Then click ??Show Project.?
Geographic, date, order and class, and other information is in the header. A map of points are shown directly below. Below the map I??d choose ??List Bench Marks?. You can choose either the Passive Mark or Datasheet option for comprehensive information. I prefer the Passive Mark page.
You can directly download the observations, BM data and project metadata thru links at the bottom of the page.
In order to organize data for processing and adjustment, points participating in a project are given a unique 4-digit identifier. This means that you need to find the point/points idenfier in order to understand the observation data.
Note that the observations available include sections subsequently rejected for not meeting specifications.
These field observations are the raw observed values for each section of leveling. Raw field data has corrections applied, observations are converted to geopotential units and constraints are applied during the adjustment.
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Thanks GeeOddMike. You did infer incorrectly, I'm well aware of how to track down NGS point information. I'm not involved with the control side of the project so I didn't even look up the BM data. My portion is strictly boundary based.?ÿ Using the control of course.?ÿ?ÿ
