My vote would be no new SPC's. We should be able to move beyond that and still use the NAD83 SPC's if needed. Hopefully we will be able to move into a 3D world.
The SPC's converted directly from lat and long were never stable on the ground. Every time they adjusted NAD83 or fine tuned the system anything you had fixed on the ground moved a bit in it's SPC coordinates. I suppose on a dynamic earth you can't have total stability.
> Land Surveyors are minority users of reference frames. If we aren't careful Engineers will bypass us and get the data they need the way they want it...
Bu11s#!t.
Engineers don't know what they want. Come on. Bypass us?! Surveyors, whose job it is to understand reference frames, don't understand reference frames by and large. Civil engineers are going to understand reference frames? I would expect only a minute fraction of civil engineers understand reference frames compared to surveyors.
> My vote would be no new SPC's. We should be able to move beyond that and still use the NAD83 SPC's if needed. Hopefully we will be able to move into a 3D world.
>
> The SPC's converted directly from lat and long were never stable on the ground. Every time they adjusted NAD83 or fine tuned the system anything you had fixed on the ground moved a bit in it's SPC coordinates.
But that is true regardless of how you express a geodetic position. The only way around it is to modify the coordinate system (as you describe), but the geodetic position is still moving.
I'd say surveyors knowledge of reference frames is improving, while engineers, architects etc. is staying about the same. Continuing education and Degree requirements being the main reason for the improvement. Still a long ways to go.
So if you wanted some sort of county wide stable coordinate system you'd tie it to hard monuments in the ground. Your origin point would be physical with multiple backup monuments. You'd have some monuments out at the edges which you could check every so often to see if the earth is rotating (deforming). Then you could redefine (adjust) the LDP parameters when needed to keep your coordinate system as stable as possible. Not that hard to do but not ideal for the one size fits all forever crowd.
> I love the idea of a county based reference system, but I do not think it's completely feasible. It may work in the larger western states, but it would most likely cause chaos in small states, like mine (NJ).
>
> From my viewpoint as an engineer, throwing (what amounts to be) 20+ reference systems at me would get tiresome and complex, especially when possibly involving projects that cross county lines (though I do not know how this is handled elsewhere in the country).
>
> From my viewpoint as a land surveyor, scale factors are reduced greatly etc etc. I see all the benefits here.
>
> In the end, I think it comes down to how well the engineering community accepts a new reference system.
>
> Or maybe I'm just missing the point... if I am, anyone willing to show me the pros and cons of this?? :-S
A few years ago Ohio Department of Transportation (ODOT) proposed a single state wide projection to replace the two zones currently used in Ohio. The reason for this was difficulty with ODOT projects that bridged or connected to prior projects that had bridged the existing zones. Exactly the problem Sabre970 mentioned above.
The plan was well thought out and full description of the technical details were posted online for comments. The information was on the ODOT aerial mapping/surveying portion of their web site. The link required a pass code to view the details. That pass code was widely distributed to surveyors and engineering consultants. I don't know if there were many comments and believe the proposal is now a dead issue.
> So if you wanted some sort of county wide stable coordinate system you'd tie it to hard monuments in the ground. Your origin point would be physical with multiple backup monuments. You'd have some monuments out at the edges which you could check every so often to see if the earth is rotating (deforming). Then you could redefine (adjust) the LDP parameters when needed to keep your coordinate system as stable as possible. Not that hard to do but not ideal for the one size fits all forever crowd.
I'm not suggesting any of that. A coordinate system, in the sense we're discussing (e.g. Texas Coordinate System of 1983, North Central Zone) is a reference frame and a projection. The reference frame is defined by NGS (NAD27, NAD83, NAD2022, etc.) and the local people have no control over that. The geodetic positions in that frame will move (either by actual motion or refined measurements). The projection simply equates a grid value to a geodetic value.
Having said all of that, I am absolutely in favor of having ground monuments. There is still a great deal of relevance for precise ground stations.
You need to think beyond the typical use of the term 'engineer' and consider who else compiles and uses data. Professional Land Surveyors in North America are a drop in the bucket. We are also generally less advanced in our knowledge on the subject than the other users. Howl all you want but that's the way it is...
I know you are not advocating that Shawn. It's nice to talk with someone that really understands what is going on with these coordinate systems.
One thing one needs to understand about SPC's is that long term in much of the country an SPC is not a stable fixed point on the ground. Might not move much but they will migrate. It's one reason I'm not a fan of SPC's.
I'm confident that we will all come along and be able to deal with it. In 7 years hopefully the education will have caught up with it.
My little LDP's are tied to a physical marker on the ground. In 20 years the geodetic coordinate will have changed a bit. Just update the lat long of the LDP origin to the current one and the coordinates should fall right in place. It's pretty simple really.
Right on Leon. I plan to do the same thing when 2022 comes along.
Shawn,
Go to item #19 at the list of articles. Or, buy and read the book (but all the information is posted on-line.
There are no secrets, there is no projection (other than using the plane surveying latitudes/departures with respect to the standpoint), no zones, no scale distortion, and no elevation factors. The solid geometry equations are time-honored and give the user the ability to view any point "in the cloud" from any point selected by the user. What you get is the local tangent plane horizontal distance and the true azimuth from the standpoint to the forepoint.
The entire system is already in place and being used. But the software vendors have yet to get on board. I'd rather see the user understand what they are doing than to buy and use "black-box" capability.
A quote from Chapter 1 of the 3-D book, "the end user is free to use the term "BURKORD(TM) as applied to the underlying database or to software obtained from Global COGO, Inc. However, anyone offering a product or service to others whose value relies upon or is enhanced by reference to or use of the BURKORD(TM) trademark will be expected to pay an appropriate licensing fee."
The GSDM is simple, complete, and rigorous. Yes, the GSDM uses a BURKORD(TM) data base. But, each end user is expected to invest sufficient "brain power" to understand the geometry of spatial data. It puts the user in control - could it be you don't want that?
What you get is the local tangent plane horizontal distance and the true azimuth from the standpoint to the forepoint.
That's what I was referring to regarding the temporary creation of a temporary projection.
Also, I'm not against anything if it works. I've been advocatin LDP for a while because of the flexibility presented to users.
> Right on Leon. I plan to do the same thing when 2022 comes along.
Yeah, you dudes will always be able to use a 5000, 5000 coordinate system. I wouldn't worry about the new datum.
You really should try to get Javad to make your System an option in their new GNSS system. They got the smarts and the programmers to do it. Once you get one major on board, surveyors will try it. If they like it it could happen. Otherwise you may never see it go.
I'd like to try your system but I ain't gonna program it all up from scratch, maybe 30 years ago but not now.
I like having a geodetic database in which points can be recalled and projected (or not projected) in any system the user desires. It's the future I believe. This is mostly how the database works for Javad's data collection.
One kink in this, and it's significant for engineering, is the handling of horizontal curves. The rate of change in convergence is different for every projection depending on its geodetic origin. This causes the relationship between points to vary (perhaps only slightly) from one projection to another. You'll notice that GIS software doesn't support arcs, but segments them into chords. Changing a drawing from one projection to another will cause tangent arcs to no longer be tangent. Something has to give in the re-projection.
If you slice a cylinder perpendicular to its axis you get a pure horizontal curve. Change the slice orientation a bit off from perpendicular and you no longer get a pure horizontal curve. Such is reality when dealing with projections. Yup, keep the raw database in world coordinates and choose how to deal with distortions from the unlimited possibility of projections from there.
What I need to explore further is how the Javad database is going to interact with office software. Can I maintain that database right into say, doing design work with AutoCAD or MicroStation based packages. How hard is it to go back and forth, import, export and all of that. Seems like in the end one common database supporting all systems would be ideal but maybe wishful thinking.
Add the geometric location of the radius and PI to your data. It won't make curves tangent in all projects tons but will make them definable..
The radius will be different between at the pc and pt. Three point definition (such as pc, pt and midpoint) is better but the curve will change as it is re-projected.
Carlson SurvCE doesn't work this way and I'm pretty sure Survey Pro doesn't either, but I could certainly be wrong. Carlson stores LLH in the raw data file. But the points are stored as grid projection coordinates. No ability to import as something else nor export as something else.
I have minimal recent experience with Leica and Trimble software.
Mr. Day, I feel the same way you do,
but without the proper metadata on the report, it will become very difficult to "follow in the footsteps of the original surveyor."
