@mightymoe So you believe that a position on the Clarke 1866 ellipsoid should have the same coordinates on the GRS80 ellipsoid? The ellipsoids have...

@mightymoe This may help. NAD27 is indeed on the Clarke 1866 ellipsoid, but the center of the ellipsoid is not near, let alone at, the center of the...

@mightymoe Hmm How do you define "on the ellipsoid"?

@mightymoe Agreed, there is no mathematical connection between 83 and 27. What I study is the connection between GRS80 and state plane grids and the...

@mightymoe OK, I see. When you criticize NAD27, NAD83, or any state plane system, you're speaking of the totality, the data, the coordinates, the co...

Too long a story to tell, but math and surveying were first woven into the fabric of my mind by elementary trig in high school and B-grade western mov...

@olemanriver An interesting area. Looking along ol' Highway 58, also known as suicide alley in older days, for the few complete control points, the ...

@mightymoe I can understand that. I've seen a lot of data sheets for monuments both here, in Montana and other states that show 5 decimal places in s...

@mightymoe Right. I stand corrected on the 20,906,000 number. The 1945 instructions dictate that number. Consider now these distance calculations f...

@mightymoe You said: "The radius of the earth used for elevation scale is 20,906,000'." There is no "elevation scale" in NAD27. There is a scale f...

@michigan-left Indeed. In the 17th and 18th centuries, the most valuable asset for a sea captain was an accurate map. Mercator developed one in 1659...

@michigan-left No, and the licensing requirement in NC and other states doesn't seem to be guaranteeing their competence either.

@mightymoe Now, Moe, you're arguing against yourself. Above, you said, "Z is there, you had to have Z." Now I'm not sure what you're arguing, but I ...

@rover83 You can take heart in the fact that most GISers have less understanding of map projections than the average surveyor and need to be experts...

@norm I would rewrite part of your takeaways. Neither TM nor Lambert state plane SPCS have parallel meridians. A Mercator projection has parallel m...

@mightymoe Well, yes. Actually, the methods for calculating state plane coordinates from lat/lon are very different along with the absence of ellips...

@mightymoe In the NAD 27 days, I think, x was Easting and y was Northing. The terms Northing and Easting came later. For DQ3133, NAD83 (2011) (Nort...

@mightymoe Fascinating old data sheet! It doesn't have the 3d XYZ coordinates; they had only 2 dimensions to work with.

@michigan-left Yes. But using metric is like everything else we've discussed here. Solving a problem often creates at least one more problem

@michigan-left Look at the differences between the XYZ coordinates between the NC plane and the MT plane in your post on 3/24. Those differences are...