This old surveyor was including grid coordinates 24 years ago to aid in recovery.
Never used to do anything with SPC. Purposely kept off of it.
Moved to a new firm, and this place is all SPC. They have records 30+ years old with SPC, and the break downs of sections, etc. It is very helpful.
It's interesting reviewing the statutes for this nomenclature; it looks like North Carolina recently updated the naming convention. I don't quite understand why 102.1.1 was repealed but they updated the statute effective 7-10-23. The statute states that the new name is to be the "North Carolina Coordinate System of 2022". It further defines 2022 with a location of the Lambert system and scale factor. However, later in the statute (102-1.2.) it states that for coordinates used in description or identification of surface area or location within this State the coordinates shall be identified as "NATRF2022" or "NAD83" or "NAD27".
I find the statute confusing.
Now, I'm no absolute defender of either NC statutes or procedures, but this one passes my personal muster.
Note that in prior state plane systems, Lambert projections were defined by a central parallel and two secant parallels, the north and south standard parallels. Changing the definition to a central parallel and scale factor is an improvement.
The new definition allows system designers to define the central parallel simply (without excessive decimal places) and also to set the accuracy (1:10000, for example) at the central parallel.
Under the old definition, north and south standard parallels were determined simply and the latitude of the central parallel was calculated. If you refer to Stem's publication 5, you will see the unwieldy result for the central parallel in NC.
The same reference will show that the resulting scale factor at the central parallel does not meet the 1:10000 criterion.
As to projection names vs coordinate descriptions, NAD doesn't correspond to rhe current name for the NC State Plane Corrdinate System, either. I suspect thar similar divergences appear in other states also.
In any event, Lambert projections can be defined by either defining standard parallels and computing the central parallel or by defining the central parallel, assigning a scale factor to it while ignoring the resulting standard parallels.
If you look at the Lambert zones in states like Iowa that have many LDPs, you will find that those zones are defined by central parallel and assigned scale factor. As an aside, all Lambert projections, including the current NC state plane projection, can be defined by a central parallel and its scale factor.
It's all just applied mathematics, and that's the easy part. The hard part is what surveyors do; use the resulting projections to produce a valuable product.
I'm only concerned about the naming convention. Are they wanting it to be named "North Carolina Coordinate System 2022" or the "North Carolina Coordinate System NATRF2022" or "NATRF2022". The first name seems to be the sweet spot, the second seems to be redundant, and the third doesn't give enough information.
The Montana code is more precise as it mandates the new name to be the "Montana plane coordinate system". The older systems are the "Montana coordinate system NAD83" and the "Montana coordinate system NAD27 (zone north, central or south)". I'm assuming from the new name 2022 is only going to have one zone like NAD83. Not a fan!!!
Overall, this is another great video. I would make a few comments.
First, you can almost always be certain that the metadata will be lost as soon as engineers or their ilk get their hands on it. I can not tell you how many times I seen plans based on my design surveys included in plan sets with none of the metadata attached.
Second, maybe I misunderstood what you were saying but you can most certainly derive a project combined scale factor from multiple locations within a project. This often provides a solution minimizing distortion over the entire project area. In a smaller area with minimal vertical relief a single point might work but not so much for larger projects.
It is best to scale about 0,0,0 and then truncate the resulting coordinate to ensure the resulting values are not confused with the grid values. See my first comment for reasoning. I have always disagreed with, the rational with scaling about a particular point to allow for inclusion of some data on an actual projection. I contend that you could just as well translate the data to fit the project coordinates, the distortions will be the same and when your values are released into the wild they will not be confused for something they are not. It makes even less sense now with CAD systems that let you specify how your project coordinates are transformed from projected grid values.
Remember, friends don't let friends scale grid coordinates without truncating.
I agree with John that we may assume that any metadata we offer in our submissions will be jettisoned by the time final plans are generated.
And while I see his point about scaling about 0,0 and truncating I also understand why people scale about a point central to the project and don't truncate. Doing so leaves a survey that will fit to GIS planning level stuff that designers rely on so heavily while having true ground distances - as long as the project area is contained within a few square miles. Which is most of them. It's a PITA, but that is just our cross to bear. Low Distortion Projections address this scaling problem very nicely.
...I also understand why people scale about a point central to the project and don’t truncate. Doing so leaves a survey that will fit to GIS planning level stuff that designers rely on so heavily while having true ground distances – as long as the project area is contained within a few square miles. Which is most of them. Low Distortion Projections address this scaling problem very nicely.
This is the easiest way to make the GIS people happy.
Yes I agree. It should not matter if you scale about 0,0 or a point on site and if you truncate. GIS people should if given the location scale and all other information should be able to build that mini datum right back to nad83 state plane easy enough. Most GIS people I deal with the ones who come to survey conferences and such understand that the LDP is gold but that requires their techs to have the information to build that in and suck it in.
