Think about that for a minute. Population has nothing to do with elevation or scale. In NC, all the new projection does is relocate the origin to bring points near the central parallel into 1:10,000 spec.
Now there is a provision for LDPs that do have a population component. As I understood it before the train quit running, the most populated areas have the most demand for highly accurate work and limiting LDPs to those areas would limit the proliferation of LDPs. But it's not an easy task to complete in a given area.
I've often thought that the real purpose of the project was to eliminate the survey foot and use east longitude instead of west. But I've always wanted to visit Roswell, NM, so any of my thinking on this should be ignored.
I believe you're correct Mathteacher. But there are more things afoot. The push is to put 0degrees longitude through Rosewell, NM. Then things will finally align and the world will actually turn flat.
Plus: they aren't dinosaurs, they're dragons, and Pluto IS a planet.
Think about that for a minute. Population has nothing to do with elevation or scale. In NC, all the new projection does is relocate the origin to bring points near the central parallel into 1:10,000 spec.
Now there is a provision for LDPs that do have a population component. As I understood it before the train quit running, the most populated areas have the most demand for highly accurate work and limiting LDPs to those areas would limit the proliferation of LDPs. But it's not an easy task to complete in a given area.
I've often thought that the real purpose of the project was to eliminate the survey foot and use east longitude instead of west. But I've always wanted to visit Roswell, NM, so any of my thinking on this should be ignored.
you are correct on the math part. Go and watch some of Michael Dennis webinars on the new state plane. They weighted it and tilted the planes to achieve the lowest distortion based on population at the surface. Nope it’s not mathematical more political. But that’s what they did. but you are so right that population has nothing to do with the elevation. Just like the shape of a county has nothing to do with what zone you are in from a mathematical standpoint that’s zone is a political boundary look at the VA map of zones for nad 83 state plane then place your math hat on and look at the parallels. Look at Caroline county Va. right or eat of the meridian south of the lambert yet is in the north zone. The new state plane is a different animal and yes math is in it but they weighted how and where the minimum distortion between grid and ground are at the basis of the heavier population.
I tried telling the folks here to adopt LDP’s for our state. But they wanted to keep it the same. So we end up with north and south like always and of course the one zone that many use in all of this. Probably great for energy electric companies to have one zone. And from a GIS standpoint.
https://repository.library.noaa.gov/view/noaa/56898/noaa_56898_DS1.pdf
here ya go @mathteacher This is what I was referring to on population it’s not just that but it was utilized within the design all within the first paragraph or so.
@mightymoe well ground has its own issues as well. Every time you set up a total station you are technically defining a new plane as gravity is not the same at every station period yes it’s minimal but the other technically correct fact is there is no such thing as ground coordinates. Even if you assume coordinates you are on a plane. Ground coordinates if they existed would be along the slope of the surface which stopped being done around the 1936 ish here in colonial state and all was done to reduce to a horizontal plane. Our exams do not shoot on a horizontal plane they shoot slope. We mathematically calculate the horizontal and we assume the earth is flat and we are always plumb to gravity and it’s the same no matter where you set up your total station or your level or even the 4ft carpenters level we assume it’s the same because it’s minimal at our location or project site. The truth is we don’t have a flat earth and the geopotential surface is ever changing and it will continue to change. Therefore we lie to ourselves and say this is good enough. I don’t argue with that at all. But what I do know is we are able to now measure that difference very repeatedly and accurately if done correctly and in the future I am sure there will be folks like you and me sitting around saying what the heck where those folks thinking didn’t they know the world is not flat why did they not just measure and call this tuff for what it is mark to mark or whatever they decide on and they will be undoing our flat ways and complaining for years to come.
Yes, and it does that in NC. It was surprising to me (I had never thought about it) but neither the 1927 nor the 1983 versions of the NC state plane projection met the 1:10,000 criterion on the ground at the origin. The 1922 one does.
The great step forward in Lambert projections is using an assigned origin scale factor to compute the mapping radius at the origin and then letting the north and south standard parallels fall wherever they may. In the traditional derivation, the meridians of the standard parallels are determined first and the central parallel falls wherever it may. That change allows the origin to be placed easily at any distance below or above the ellipsoid.
I didn't mean to be snippy or sarcastic. You know more about applying this stuff than I can even imagine. I think that I overlooked taking my daily crazy pill that day, so some craziness bubbled up.
@mathteacher oh I didn’t take it as being snippy. I don’t take things personal at all. Value your input tremendously. We are all here to learn the way I see it. I have a lot to learn still.
There will come a time where everything is based on Lat, Long, Elevation. That's real surveying. Ironically, the GLO/BLM did the entire PLSS that way, then along came the button pushers who can't figure out how to do it.
We have had LDPs in Oregon for a dozen years now. I do all my work in the one appropriate to my area. Differences between grid and ground are miniscule, so there is none of the old scaling to ground BS necessary. I can't figure out why anyone would oppose their use. Yet most people still insist on using the old state plane and scaling it. Portland is pretty far from the SP grid origin, so scale factors and convergence angles in that system are rather dramatic. Old habits die hard.
It was surprising to me (I had never thought about it) but neither the 1927 nor the 1983 versions of the NC state plane projection met the 1:10,000 criterion on the ground at the origin. The 1922 one does.
That's because the original design for state plane anticipated everyone would reduce ground measurements to sea level. There was no 1: 10000 criterion on the ground. It applied to the scale factor only and did not consider the elevation factor. That's why the datasheets give you a factor to put ground on grid, not the other way around which is where it evolved to with at your fingertips GNSS measurements.
It was surprising to me (I had never thought about it) but neither the 1927 nor the 1983 versions of the NC state plane projection met the 1:10,000 criterion on the ground at the origin. The 1922 one does.
That's because the original design for state plane anticipated everyone would reduce ground measurements to sea level. There was no 1: 10000 criterion on the ground. It applied to the scale factor only and did not consider the elevation factor. That's why the datasheets give you a factor to put ground on grid, not the other way around which is where it evolved to with at your fingertips GNSS measurements.
It was way more intensive to survey with state plane prior to computer programs doing it all for you. Learning to reduce instrument data to geodetic coordinates, then further calculate State Plane coordinates from them was the correct way to survey.
I was able to get graph sheets of calculations an older surveyor did as I followed his work trying to replace some corners he had found. Those corners fell in what is now mined and reclaimed sites. What was interesting was he calculated coordinates that looked like XY except they increased to the west, basically a Northing, Westing system. Eventually it dawned on me that they were converted Lat, long coordinates. When I began to add true north to them they started to fit much better. Those sheets were from the early 1930's. I really doubt that the network of NAD27 state plane was around then. It should be humbling to know that old timers like that surveyor were more advanced mathematically than today's button pushers.
@mightymoe You are so correct. That those old timers understood and did math Longhand without a data collector without a calculator even. Maybe they had some slide rules. They reduced everything long hand. Field notes were more than just numbers angles and distances they were the story. They laid out the whole picture and described what was and what was going on around the them.
I honestly think that everyone should take at least one traverse doesn’t have to be long maybe like 5 to 6 setups. Recording all information HZ angle zenith angle slope distance. Temp pressure height of instrument height of target. Then reduce all the measurements by c/r corrected zenith angle from height apply the ppm temp pressure etc. reduce to horizontal distance. Then reduce those distances to sea level and recompute all coordinates at the state plane nad27 is fine. It truly is not that hard. It’s basic math. Heck horizontal and vertical curve math is more complex that the state plane coordinate system or UTM. MGRS etc. working on the ellipsoid is not that hard either. Heck how many surveys were done in colonial times that not one coordinate was computed. Is we have hand held computers data collectors with more power and computational power than my first computer. I understand why we use a plane system whether or not it’s on state plane or sudo ground so assumed. It’s easy math it works for drafting systems etc. it made for easy computations on the hood of a truck or suburban. I find it humorous that when NAD 27 was published and cities towns started adopting it that surveyors reduced ground to grid and now we can get grid straight out of a box and we go the other way. I do understand that it is not a perfect system for everything we do project wise. Distortion could cause issues etc. Also depending where you are and how close to the ellipsoid you are could be extreme . Here many places it would not make a hill of beans in the big picture for a project.
OleMan, even more on point is to teach yourself geodetic calculations from your measurements. I don't really know how the old timers did it, I know the solar compass was used. And frankly, even though I did do those computations for a bit in my early days of traversing long distances, computer programs for the 48 were out by maybe 1980 or 81. After that I would plug in my observations, calculate Lat, Long, from there plug in the lat, long into a second program that would spit out the State Plane coordinate. That's the proper way, forget about scale factors ect. Or even go more old school and triangulate. The government published booklets for each state. In it were all the scale factors to interpolate grid scale and formulas to properly calculate.
Most never applied the second term or LaPlace corrections. And certainly, I doubt there are many left that triangulated.
After reading all these posts I have to set up a test range in the office parking lot. I have to experiment with all the different data collector settings addressing grid, ground, and scale factors. Just reading about these things isn't good enough for me. At the jobsite this past Friday I got an 0.08' difference between control points set by RTK and total station distance. The control points are about 300' to 400' apart. This thread has been a real education for me. Many thanks to you and the other respondents.
Correct, and sea level under NAD27 was effectively the ellipsoid. There was one tie of the geoid to the ellipsoid and that was at Meades Ranch. However, the Clarke 1866 ellipsoid was reasonably (?) close to the geoid in the continental US.
The 1:10000 criterion was between the NAD27 state plane and the Clarke 1866 ellipsoid. It's one reason for states having multiple NAD27 state plane zones, something carried over to NAD83.
One goal for the 2022 redefinition is to move the state plane closer to the topographical surface to further minimize scale distortion, but that also moves the plane closer to the ellipsoid at its origin.
NC rejected multiple zones for both NAD27 and NAD83, choosing instead to live with added distortion in the southeastern part of the state while also losing the 1:10000 criterion at the origin. NAD22 cures the latter but not the former.
Thanks for clarifying that error on my part. It's been a while and my Prevagen is wearing off.
That's great, but be careful! The ambiguity over Trimble Access and its handling of state plane as the projection and 1 as the combined factor brought Microsoft Copilot to its knees.
The combination of Access reporting state plane when no combined factor is entered and doing the same thing if 1 is entered while doing something different when 1.0001 is entered was too much for Gates' baby to resolve.
I let it grind for 15 minutes with no results before I shut it off.
After reading all these posts I have to set up a test range in the office parking lot. I have to experiment with all the different data collector settings addressing grid, ground, and scale factors. Just reading about these things isn't good enough for me. At the jobsite this past Friday I got an 0.08' difference between control points set by RTK and total station distance. The control points are about 300' to 400' apart. This thread has been a real education for me. Many thanks to you and the other respondents.
.08' in 300' off the top of my head is 267PPM. This is a gross error, you would need to be +5000' above the ellipsoid for that to work because of scale factors. Clearly, that's not the issue in Florida. So it's bad RTK shots, badly imputed scale factors, bad total station shots, terribly out of plumb tribrach, terribly out of plumb rod bubbles, or a setting in the total station such as PPM, temp correction, prism offset.
Tape out 300' points in the parking lot if you have a big one. Use that to check all these settings.
My guess is either a bad total station/prism setting or a bubble. Should have nothing to do with Scale Factors.
To check prism settings set up two tripods over close points. Measure the points with a tape, say 24.25 feet. Measure between the total station and the prism with the same tape. Try to keep them the same height or close, you should measure 24.25 feet. If your total station measures 24.17', that's your issue.
@mightymoe "To check prism settings set up two tripods over close points. Measure the points with a tape, say 24.25 feet. Measure between the total station and the prism with the same tape. Try to keep them the same height or close, you should measure 24.25 feet. If your total station measures 24.17', that's your issue."
I do a very similar check on prism constants but I use 2 marks on my concrete driveway. I lay the tape on the concrete and get the slope distance which IMHO is easier to measure accurately than level. I set up the gun and a second tribrach/prism, measure heights and distance and and check the calculated slope distance on the DC compared to the taped slope distance. I also rotate the tribrach/prism 90 & 180 for a check on the optical plummet. Occasionally I leave the tribrach/prism alone and rotate the tribrach/gun 90 & 180 for a check on it's optical plummet and so far it has been +/- 0.002'.