The software has the convergence angle and what it needs to calculate the geodetic azimuth and grid azimuth.
The rotation is adding or subtracting.
That's what it seems like to me, but I was programming computers before computer science degrees were available at more than a handful of universities and the biggest market for computers was for accounting.
Now the few lines of code is in the surveying software and it all may actually be there now but not widely known.
In the case of CAD, it may be harder; a branch here, a jump there, and a multiply or two and 450 pages of documentation.
I believe this was all tossed in with the general term "alchemy" back in the day. A dozen different people take on the same task and arrive at a dozen slightly different answers.
I believe the state plane system did exactly what it was intended to do. It was designed to keep math simple in the days of mostly hand calculations so the plane mapping system to keep things as close to geodetic as possible. The only thing the ground had to do with it was reducing the distance along the surface to ellipsoid. Surveyors on the boundary side and construction side nor engineers accepted that geodetic as the gospel. On the non geodetic surveying side we kinda play its flat enough or close enough. Which at the time the first state plane system was put in the difference of grid and ground was negligible because of the chaining and poles Also the system was perfect at that time for highway projects and the like We have simply out grown the system because we can position things within such a tight tolerance over miles and miles today. But we still have to give a large amount of credit to those who designed the system because it still works today if it’s applied correctly. It actually could be simple to i theory just do everything in state plane period design boundary etc etc And yes that would make some properties just shrink in size but it could be done. And yes we need to follow in the footsteps as well which can be done also the one thing that always gets mentioned is the distortion from ellipsoid to the plane grid or from geodetic north to grid north. We have to be on ground because of distortion Well let me open a can of worms If you think surveying on ground is not distorted then you are fooling yourself . It is the very reason we have professions of geodesy and geodetic surveying etc we have just accepted that surveying on ground is more accurate subconsciously I guess . Now we are developing a system that the distortion will be smaller at the ground to grid level in areas but further from the geodetic datum . Maybe LDP is the best answer. Have a datum that everyone is required to tie to period and simply instead of assuming 5000 5000 create a ldp on every job and that way when junior gets the project next door he can see your ldp information and it will all tie on the datum side I mean they created the system in the 1900’s this thing state plane if used correctly is awesome But it boils down to time = money No way around it i see And not everyone has the education to understand it either There are some top notch surveyors probably still out there today that have more brains than i could ever but they might have never ever use a system like state plane i knew several that had been around and every job was the same assume north 10000 east 5000 and run around a boundary hold a plat bearing and then everything was on that forever throughout design etc . Maybe we could design a new unit of measure that had a scale in it that could be the fix lol call it something we have 2 feet had several definitions of the meter change. Chains veras hands poles . Wheels how far a horse could walk trot I am amazed after working all over the world and seeing different coordinate systems designs datum’s mapping projections used etc . I mean the people who did these things are some very intelligent people and they had enough compassion to create a system for a dummy like me to understand .
"And yes that would make some properties just shrink in size but it could be done."
How would using state plane make a property shrink?
At the time the SPCs were designed, they probably didn't have the data in m manageable form to design LDPs. A card file of coordinates and elevations is not like a computer data base. Even with the data the calculations to find good parameters would have been arduous.
If that had been practical at the time, I imagine they would have done it.
A couple of inches per half mile tends to add up. Seriously.
One guy lists a distance of 2639.41 between monuments and the other guy says it's 2639.57 between the same two points. One creates the description and the second comes along later and reports all description distances are off by varying number of hundredths. One is writing descriptions in State Plane, the other one is using direct measurements with a total station.
@mathteacher if we are on grid the mapping projections. The distances are shorter so the square feet will be less and acreage will bel less numerical not in physical. Than if we measured the same lines at ground. Also this gets to the understanding of mapping projections themselves. No one mapping projection can hold all truths. Size shape distances directions. If one is aware of what mapping projection they have and where what all is needed is equal area direction etc. and where it is not then it again is simple math. I can’t remember now but take a larger area and simple square and compute the area length x width at grid. Then do same at surface. I believe the math is square of the combined factor or squared root of it divided or multiplied to do the same thing as we do with distances. Not all properties are square and not all are at same elevation around property. For a long time i never even carried elevation assumed or otherwise on just a boundary survey. I have one coming up that id did a rough check on that i would affect the acreage enough that i will have to do my computation for the acreage at ground. I guess poor grammar here of stating property would shrink could have been clear. Not physically the property would be what it would be. But using grid distances to close it would change the numerical value vs same thing at surface or ground.
One is writing descriptions in State Plane, the other one is using direct measurements with a total station.
Using SPC distances on a plat WITHOUT NOTINGTHEM as such should be cause for disciplinary action. Doesn't every state call for ground distances?
I'm close to you on RX0088, I get 4.57 ppm, but we're pretty far apart on RX1056.
I think it's west of the airport with distortion of -147.5. It's 1,000 or so meters higher than RX0088.
It's a good example of what @mightymoe is talking about. It's also a good example of how a standard state plane distance calculation can be advantageous in mountainous terrain.
That's what I get too. I gave you the wrong station. I was looking at one 12 miles east at a lower elevation. Please don't take this wrong. It might be advantageous in a mathematical sense but not necessarily a practical sense for reasons or excuses already made.
But that's the point of this whole discussion. NAD83 is not designed for measurements on the grid to be equal to measurements on the ground. It's impossible to create such a projection for an entire state.
To use state plane, you have to first understand that the plane is not the topographical surface. Then you have to know how to convert between the two. That is why we have scale factors and elevation factors.
A calculation of acreage using state plane distances shouldn't even be considered; it's meaningless.
But state plane distances won't always be less than ground distances. Beyond the lines where the secant plane intersects the ellipsoid, grid will be greater than ground.
No problem. Thanks for testing that hastily designed LDP.
The topography changes rapidly out west. We have a little of that here, but 5,000 feet here is exceptional, 2,500-4,000 fairly common.
Any LDP in the Rockies is bound to be limited in size.
