TRUE SPCs are a complex animal and are rarely needed for most projects under 6 miles in length. Mixing them with terrestrial measurements almost always bastardizes them. I agree with Kent though and think if you can't deliver the real thing, then don't make them look like it.
You Deliver What The Client Wants...
...or don't take the job.
Paul in PA
> NJ DEP requires the State Plane Coordinate of the Point of Beginning, the Bearings to be in State Plane Grid, but the distance to be ground, for all Green Acres Projects.
>
> Not the greatest of methods. The last project I did I tried to talk them into either a LDP at ground level or State Plane at Grid. I didn't get anywhere with them.
Just Wondering why an LDP in NJ?
Ralph
You Deliver What The Client Wants...
Exactly!
I'm all for this attitude-leaves more work for me. And those jobs are great! I do them all year long and won't complain or get on my high-horse about the surface coordinate system.
The almost reverence attached to ZY grid values which don't reflect ground conditions frankly makes me scratch my head.
They had a neat low distortion projection here called the New Zealand Map Grid. It was highly optimised to fit NZ's long thin twisted shape
But the maths was rather complicated - a power series of complex numbers.
So now they just UTM - never mind that the country sits in three zones - we'll just use the middle one and ignore the distortion around the edges 🙁
You Deliver What The Client Wants...
> The almost reverence attached to ZY grid values which don't reflect ground conditions frankly makes me scratch my head.
Okay, I'll bite. How do you express coordinate positions in some survey description that is to be of record, then? That is where the power of the standard projections of the SPCS lies. There is no need to recite some arcane recipe (two mouthfuls of tequila, one dash of bitters, a dot of salt ...) to allow someone else to figure out where in Hades you were. Standard projections are extremely efficient in that respect.
My opinion is, there are only one kind of State Plane Coordinates. All else is a masturbation and figuring out what the jerk off did to change them.
Pablo B-)
> My opinion is, there are only one kind of State Plane Coordinates. All else is a masturbation and figuring out what the jerk off did to change them.
>
> Pablo B-)
:good:
How ?
What the client wants is an SPC for the POB and ground bearing and distances relative to that position and system. If you so care you can express every corner in SPC coordinates but they would in fact not match the coordinates derived from the POB and the description. The client however is free to discard them prior to recordation.
Paul in PA
You Deliver What The Client Wants...
If what you want is to power up the GIS for any flavor of projection what you need is 3D geodetic coordinates. That is the root of everything for modern mapping.
I don't care for SPC's because neither the bearing or the distance is very real. It gets worse as the elevation gets higher and as you get further from the central Meridian. If the SPC coordinates are only published in 2D (what they are designed for) then the true 3D vector can't be calculated (but maybe estimated by using an estimated elevation, which is just more hassle).
But, we been here done this, eh?
I can certainly get to some spot on the earth given good SPC's. With good 3D geodetic coordinates I can get to any SPC and a whole lot more.
How ?
> What the client wants is an SPC for the POB and ground bearing and distances relative to that position and system.
I'm at a loss to know what the problem is alleged to be. In the metes and bounds descriptions I write, I give a list of the SPCS coordinates of the points described. I give the average value of the Combined Scale Factor that I thought was an appropriate value for the project and (unless the project is very, very large, meaning: over about 8,000 acres or with extreme variations in elevation across it) recite surfaceish distances that were generated from exact grid distances using that average value and that seldom differ from the actual values by more than a few ppm.
If you know that every distance must be scaled by, say, a CSF of 0.999870 to reduce the value recited in the metes and bounds description to grid (and you have the grid coordinates of the terminals of the line in a nice list made a part of the description) where's the problem? Nowhere?
There Is No Problem
Bearings and distances are ground, as was the original survey.
Only sufficient SPC is provided, such that another surveyor can tie in and verify. Unless there is some need the full list is never created, i.e. no 100% conversion from ground to grid.
Why do work you are not being paid for?
Paul in PA
You Deliver What The Client Wants...
How you do it is great Kent. I would really appreciate following one of your surveys using the coordiantes you provide to get started.
However, if you work on a DOT project they will expect everything delivered in surface coordinates that can be converted to state plane by simply dividing the coordinates. That way when they do legals and designs all the inversed distances are on ground. If for some reason state plane coordinates are desired then the surface coordinates are simply converted. I'm good either way.
What I think is great is that many surveyors seem so offended by surface coordinates that they won't even do the work. Leaves more of it for me. That's what's really important, and I'm not the least bit offended.
Loyal
All of our surveys where we are on the grid with our control, so is the plat and field notes. There are no scalings, rotations and translations. All acreages and distances are grid as well as the bearings and the meta data is evident for anyone to get back to the top.
It's just easier that way and we don't molest the numbers any more than we have to.
Loyal
Your acreages and distances will be off unless all you do is close to sea level (which may well be true for you).
Loyal
Montana DOT uses the State Plane CS and just addresses ground distances on their design plans. I like their approach.
Do any other DOT's follow this approach?
z138
That one combination factor on the chart near the end of the document is larger than .8' in 1000'!
The NAD83 lambert projection for Montana was setup with one zone and they tried to keep the grid factor under one. So in the middle of the state the grid factor gets pretty large, while on the north and south borders it is close to 1.
Nothing Wrong With That
That may be true but worries me is that I am also requires to provide a DXF of the lot which they are then incorporating into the State GIS. No idea if the scale factor is being applied to put the DXF back to Grid.
An LDP allows me to work at ground distances, is just as easy to setup in the software (Carlson) as State Plane, is tied to the Geodetic and easily converted to any other system.
While the scale factor in this area is only 0.999913 or .01' in 100', I need to report out ground distances on a survey. I find it a hassle to scale up the grid distances to ground and scale down the record distances to grid. I know the software can handle the scaling but it does not seem to do it for the curves. I find it easier to just to work on ground for a project, and an LDP allows me to do this and still be tied into the Geodetic system.
Not really though Tom
The acreages and distances are accurate to being on the grid. They do not represent surface, nor are they supposed to.
FWIW, the typical elevation for my area of practice is less than 500' 90% of the time and I typically work within 50 miles of the zone boundary giving me scale factors, 90% of the time, with at least 4 9's, sometimes 5 depending on area.
The most I see is a tenth per thousand, 90% of the time. I have one project where they get kinda squirrley due to one of the higher points in the area, and being quite far from the zone line.