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@rover83 I was asked this question today. Will there be a different way to scale the new system to ground and how will we work with ground if it’s different. Will this make gps work go away. So I guess the insanity will continue. I tried explaining that instead of the projection at the ellipsoid it will be closer to the surface. So less distortions between grid and ground distances. But they will be grid coordinates and surveyors want ground coordinates not grid. We have to scale grid coordinates to ground. Somewhere somehow someone made grid this magically thing that we should only know about and not mess with and just use it only as a means to get to the ends.
Tell them it will be just like a new SPC but the combined scale factor is so close to 1 that you can ignore it.
.On the problem of getting from the globe to the grid, please consider the attached ppt and let me know what you think.
Same for anyone else.
@bill93 . Even with our system today. 90% of what is done daily would not matter if we just left it on grid to begin with. We have become so intrigued with everything we do first thing to do is have a grid coordinates system for gps and a ground scaled system for robot work. Its all the same site. But we create this two system approach and file system to keep things separated except when we throw all the csv files in cad to draft. Then it doesn’t matter. I want to be like my 3rd grade teacher and have a yard stick and every time i see someone clicking the button to scale to ground just slap the knuckles. Maybe we should invent a app that shocks someone every time they do. I know there are situations and geographical areas that we need to do this. But most of the time its really not necessary. I have been told carlson can handle in the field correcting ground distances to grid as you work with robots trimble does this. I am sure leica can. Is there any software that doesn’t have all the parameters already loaded. If they use gnss surely all the information is there. You don’t have to type no numbers to work on the projection as far as i know. I just choose nad83 state zone and reduce distance to elev/ellipsoid and if no gps data use a average height to get started for cogo comps. But I usually start with gps so i have everything it needs. How did we get to the point of using one combined factor from one point and elevation to scale coordinates. On a site. Even when i am made to do this. I usually do computations to see the best average elevation of the site that makes the most mathematical sense. And if that causes issues i raise the flag and wave. This is worse distortion than leaving it alone. Then those scaled coordinates make it to a plat. Now someone will see that and try and find a corner thats not at that location to begin the survey from.
When I stated the issue for #1 I should have said projected to the globe in reference to the globe being the ground we walk on. I appreciate the ppt. It seems easy enough to understand. I’ve been involved in this so long I may not be the best person to ask. We’ve also attempted to explain this. See chapter 2 of LDP handbook
It will be a heavy lift to make state plane usable in higher elevation states.
I suppose it’s worth an attempt but the scale of the problem will make it difficult.
There wasn’t any real reason to restrict the new (NAD83) Montana zone to grid scales less than 1, but that’s what they did. That zone is really nice south of the Montana border near the central meridian.
It’s the same in other mountain states with TM zones. The grid scale is too severe. They need to be greater than 1 at the CM raising the surface. Why would we wish to survey thousands of feet below ground?
Locally there were always distance shifts from state plane going back at least to the 1960’s. There was even a region wide number 1.0003 called Pryor that was used. A 1.0003 scale factor represents 300PPM or 3 feet in 10,000. Sometimes the statement is made that state plane was designed to get the user within 1:10,000, or 100PPM. I’ve never seen that inside any local zones. Get outside the zone and state plane can approach it. But then the rotations are large or you’re in another state.
I began using LDP’s early on with GPS since I could design my own projections.
I never cared about distances, those are easy to deal with in state plane, it’s bearings that concern me, and the 2022 design will still have rotations, sometimes very large ones in Lambert zones.
If we’re near the CM then use state plane, scale the distances to a surface near ground within 10PPM if possible, if far from the CM then it’s an LDP, I don’t see it changing much.
Eastern Montana, 4d rotations, not interested.
As you have experienced, its possible to design an LDP to fit the need. It’s unfortunate if SPCS2022 doesn’t meet the need. The point is that it is possible to get users singing to the same sheet of music with some coordination. The first step is to get all users to agree what the threshold is for ppm error and design limits based on that guided by elevation change and other considerations. Perhaps in mountainous areas 150-200 ppm is a reasonable goal for most applications. If the stakeholders have a part in design parameters, the buy in is a lot more attainable.
158 ppm (1:6300) design error will handle 6000 ft + in elevation change. 20 ppm will only handle 800 ft.
@mightymoe do you place geodetic north on surveys or grid north where you are located.
It sounds like SPCS2022 will/would have worked, but they failed to make a separate zone for said area? I don’t know. Or he isn’t up to speed on their status/progress?
It seems as if the people most likely to criticize SPC/LDP are often times the ones that confuse everything about geodesy in the first place.
I thought about ground but then decided to restrict the discussion to pure mathematical surfaces. The Elevation Factor is a ratio, but its denominator can’t be computed without knowing the ellipsoidal height, a non-computable number.
@mightymoe do you place geodetic north on surveys or grid north where you are located.
Mostly it’s State Coordinate System bearings and “surface” distances with a scale factor.
It’s rare that anyone gets coordinate data. That’s normally reserved for our engineering clients who are on-board with coordinate system design.
For a remote township type work I usually design an LDP. As always it depends on the situation. One recent project I did a COS with the origin point shown on the plat. The reviewer got upset that the point wasn’t set and wanted it erased. So I did. I listed the origin point by LAT, LONG in the notes with projection parameters so anyone can get on the bearings.
Two ranch units I surveyed recently were very close to the CM so it made sense to use State Coordinate bearings for them. I really don’t like being widely rotated from record simply to be on State Coordinate bearings.
As you have experienced, its possible to design an LDP to fit the need. It’s unfortunate if SPCS2022 doesn’t meet the need. The point is that it is possible to get users singing to the same sheet of music with some coordination.
It seems as if the people most likely to criticize SPC/LDP are often times the ones that confuse everything about geodesy in the first place.
For sure.
I don’t even care too much about whether someone used this projection or that, as long as it’s just a projection. Not a projection developed by starting with a projection that has unacceptable distortion, then screwing with coordinates and back-calculating a totally new one that is kinda-sorta-but-not-really like the original.
If you mess with a projection, it’s not that projection any more. Don’t pretend that it is. Develop a better one if you need to.
Additionally, a lot of reverse-engineered “SPCS ground projections” are rarely evaluated in the context of the entire project, or from a larger area within which the project is located. It’s common to select a random control point for CSF calculations (“we have to get the CSF from OPUS!” is something I hear often) that is not optimized for the project itself – just for one or more control points which may or may not be representative of the extent and elevation change across the project area.
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil PostmanMostly it’s State Coordinate System bearings and “surface” distances with a scale factor.
engineering clients who are on-board with coordinate system design.
I usually design an LDP.
I listed the origin point by LAT, LONG in the notes with projection parameters so anyone can get on the bearings.
it made sense to use State Coordinate bearings
I really don’t like being widely rotated from record simply to be on State Coordinate bearings.
FOR THE LOVE OF CHRIST, none of these things are consistent, or sensical?!
How much damage are you actually doing on a regular basis?
Here’s a neat website from a great resource Ive met and interacted with a long my path.
Was a huge lift for my bigger understanding of the topic.
enjoy!
I would love to use that sort of system. Local horizon system using a simple rotation matrix is even easier to model than a projection.
I don’t think even the survey world is ready for that yet. Much to be hashed out regarding geoid vs ellipsoid height, and at the very least I can’t think of any standard commercial survey or CAD package that supports such a system. Wouldn’t be that hard to implement though.
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil PostmanEarl Burkholder, Mr. Global Cogo, used to participate here but it’s been 8 years since he posted. Do you know if he is still active?
.I email with him every so often, he was the president of the SRG chapter of the NMPS when I was living in Las Cruces.
He’s retired but still engaged in the world of geodesy and definitely alive and kicking.
@rover83 Earl used to post here. I haven’t seen anything from him in a while.
He was instrumental in helping build the LDP we used at City of Las Cruces, and I posted the links here a while ago, not sure if they’re still live or if they rolled them back and discontinued the process. Would make sense, I worked there and knew of people opinions on why it was a waste of time etc…. like yeah, why would we want to move into the future of the NSRS and be completely onboard with promoting the best possible practice….
I was only a user and working on digesting the bigger portion of what it took to develop and it’s implementation.
I would love to use that sort of system. Local horizon system using a simple rotation matrix is even easier to model than a projection.
I don’t think even the survey world is ready for that yet. Much to be hashed out regarding geoid vs ellipsoid height, and at the very least I can’t think of any standard commercial survey or CAD package that supports such a system. Wouldn’t be that hard to implement though.
It’s doable with programs available, the problem of course is getting others on-board. You can create a geographic north plat with actual ground distances but it won’t close using most programs and regulators will reject them. Plus, with any significant elevation changes all points will need to be 3D to make it work. But, it’s the real future of coordinate geometry.
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