Here is how I got where I am.
Here is how I got where I am.
1.) Perform SUNSHOT, and get on Geodetic, with the sunshot.
2.) Look up convergency, to ARKANSAS state plane using the same lat lon for the Central Meridian, to compute the convergency angle.
Apply the convergency angle.
Now, when converting to SPC, the brgs are very close.
I am essentially duplicating that, with GPS.
It essentially places all my surveys on the SAME brg system, at ground.
Nate
Here is how I got where I am.
I will add, that I did a survey, with a theodolite, that was out of adjust. It was 3 miles long EW. I found out later, it was out of adjust.
So, I went back, and took sunshots on about 5 different places, and then looked up the convergencies, for them all, so as to KNOW how much error was in the angles. I wound up rotating the survey TO the sun shots, maintaining ARKANSAS GRID NORTH, as a standard. This allowed me to mostly "fix" the traverse.
Then, I saw the utility of USING the same brg sys, as in PARALLEL basis of brg.
And, I do that now with GPS.
OK?
Nate
Here is how I got where I am.
If you turned 2 sets, closing the horizon or not, of direct and reverse, your traverse angles should have been good.
jud
I agree with Sinc. Loyal got me hooked on local projections and I use them all the time now. North is north, scale factors are negligible, I can reproject into any system I need. Life is good.
Are you talking about one of those bastardized systems, often called something like "Modified State Plane"...?
No, I'm saying that when you do a HERE and place a coordinate on the base point the data collector will create a LDP system. But the default is probably a Transverse Mecator projection. That will place distances on the grid. A scale factor still needs to be applied to get the distances to surface. Without seeing how it's working I'm not positive that's what is happening, but that's what happens in my data collector. It's a grid system, but not state plane.
I think that most will eventually mature into using local grid with low distortion for most work. SPC for everyday local work does little or nothing to make a better survey, in fact the Combo Factors and rotation leave much room for error to creep in. Many will never gracefully stop using their SPC grid and will think I speak blasphemy.
jud
>Or another solution that works really well in many circumstances is to create a "Low >Distortion Projection", and use that. Both are preferable to the "Modified State >Plane" systems, where a CSF is used to multiply coordinate values, and come up with >"ground" coordinates that are different from the grid coordinates.
As long as your bearings on the low distortion projection are the same as SPC Grid then there is really no difference. I don't put coordinates on my plat. I am the only one that will see the coordinates. The SPC grid bearings are what I am after. I have been doing that for years.
James
"and then display a ground distance if necessary. "
What?
> Without seeing how it's working I'm not positive that's what is happening, but that's what happens in my data collector. It's a grid system, but not state plane.
This is your key statement.
If you're not positive of what you're doing, how are you going to equate it to anything else?
You MUST be exactly sure of what you're doing. And the you MUST know how to transfer that information to everyone who follows after. That means including ALL metadata information, in a way that can be transferred later.
This doesn't even include the (usually small) differences in geodetic realizations, but can mean a LOT if huge siezemic variations (like the recent earthquake in Japan) occur.
This is a good part of why I think GPS doesn't mean Surveying is a "dead profession"... as some are projecting. There's too much that happens, where the art of Surveying is important. It's being melded with GPS, and is why I tend to call myself a "Geomaticist" as opposed to a "Land Surveyor". But it's definitely still an art, and you can't do it with a hand-held GPS unit (or even a Survey-grade GPS unit), as some seem to think.
Most records require "ground distances". So in most locations (unless you are very close to sea-level), you can't survey in grid systems like State Plane and UTM, and then record the results.
It's a matter of history... Technology has gotten much better in the last few decades, but many land records were created using the proverbial "one-eyed goat and a rope"...
You could also say: Basis of Bearings, True North, taken at Arkansas Central Meridian.
🙂 Tut tut tut!
Nate
> You could also say: Basis of Bearings, True North, taken at Arkansas Central Meridian.
>
> 🙂 Tut tut tut!
I don't think so...
Things like State Plane are not "True North", except for maybe at the point of origin. Anything else involves a convergence angle. And if one of those bastardized systems are involved (often called something like "Modified State Plane"), all bets are off.
But you're right in that, as long as you're CLEAR on your metadata, you can use pretty much any geodetic coordinate system. You just need to be clear with your metadata.
One of the big problems we've noticed is that, as Civil 3D users, the Transformation Tab settings are NOT honored for most things - a HUGE failure on Autodesk's part. That means if you're on a "ground" or "project" system (often called a "modified state plane system" or something like that), you can't pull in aerial imagery, shapefiles, etc. This is something I've been railing at Autodesk for a couple of years now... I tend to hate the "modified state plane" systems on general principle, since I think they cause more problems than they solve, but our software has to be able to handle this "old style" stuff in an easy fashion, since there are so many legacy projects that use that terrible system. But right now, C3D can't do that. It's a terrible system, but there's too much legacy stuff out there, so C3D needs to be able to support it in an easy fashion. (And that's not even getting into the Map3D issues...)
I don't think you follow what I'm doing.
N
