MightyMoe, post: 356946, member: 700 wrote: The reason is because I want to know WHAT my coordinates are.
I don't care if they are 5000, 5000 on a point or 500000, 500000, it doesn't really matter.What is important is that I know how they are generated, and I want to be in control of it.
When you leave the office you know where you are going, you know the lat and long, you know the elevation.
So take a minute and imput into your office computer the parameters of the job, pick a lat and long near, look at the elevations and design an LPD for the project with a scale factor that gets you to the surface. Now you have metadata for the project, sitck it in the file, you now know just what your local coordinates are doing, put that into the dc, use them for the page one.
These coordinates will shift as will the elevations when OPUS or CORS are applied to the values, but the question to ask is why is THAT a problem?
Why do the values 50000, 50000 on some random control point tump everything else, including a well designed LDP?You are saying you aren't sure what JAVAD is doing to the numbers, that is not a good position to be in, heck even if Freeman Dyson is available to calculate mine, I wouldn't want him to.
The next job is a mile to the east, you imput this projection into the data collector for it and you have automatically connected local systems, you don't have to go to SPC coordinates and back them in to connect them.
But using the system described you will create two local coordinates, near to each other, both with the holy grail number of 50000, 50000 on two random control points, and both systems without metadata.
I never said that I didn't know what Javad is doing with the numbers, although there are others who are better suited to explain it. All coordinates in the LS are stored in Lat long and height, then projected to whatever projection is needed. For localization the coordinates are still internally stored as lat long.
I totally agree that working in ÛÏtrueÛ State Plane Coordinates has many advantages, and have no problem with those who chose this modus operandi for their day to day work. In fact, I wish that more folks would use SPC (or UTM) on projects (and in AREAS) where such a spatial paradigm is applicable.
I'm pushing 48 years in surveying this year (come September), and aside from a project in Maine, and another in SE Alaska back in the early 80s, SPC Coordinates have NOT been a good choice for ÛÏProject CoordinatesÛ for me. That's not to say that I haven't done a LOT of SPC/UTM Projects (deliverable) for clients, just that my day-day ÛÏretracementÛ coordinate system was NOT SPC/UTM, even though the client only saw the SPC/UTM results.
My ÛÏaverageÛ project over the years (especially since going ÛÏsoloÛ in 1985), have embraced 10-100 square miles, with elevations ranging from about 5000, to over 12,000 feet. Some of these projects having 5000-6000 feet of relief, and MOST of them having at least a thousand feet of relief. So no matter what Projection I chose, it is far from perfect.
From a purely Cadastral standpoint, the GLO/BLM/PLSS system is the most ACCURATE (and reproducible), but it does not play well with most CAD/cogo packages.
I have found Transverse Mercator Projections to be the most effective in the Great Basin (most of the Mountain Ranges and intervening Valleys run North-South), but Hotine (Oblique Transverse Mercator) Projections are quite handy at times when ÛÏfittingÛ existing ÛÏMine Grids,Û Railroads, and old Highway Projects. I rarely use Lambert Projections, but sometimes that can be the ÛÏbest fitÛ for some Projects.
In any case, the developed surface of the SPC/UTM Systems are simply TOO FAR below the ÛÏgroundÛ to be used in their ÛÏtrueÛ form (around here anyway), and the convergence angle in most cases is just TOO LARGE, and inconsistent with the Patent/Deed bearings.
While I can envision ÛÏsomeÛ advantages to holding SPC/UTM Bearings, the same can be said of ÛÏTrueÛ Bearings (although the Laplace correction is usually non-trivial here in the Mountain West)!
We are now well within the 21st Century, and with the Data Collector and Computer Technology we all have at our fingertips, I just don't see the need for ÛÏmodifyingÛ SPCs anymore. THEY either work for your Project, or they don't. If they DO, then DON'T screw with them! If ÛÏtheyÛ don't, then use a coordinate system (projection) that DOES, and be sure to put the Projection Definition (Datum, Realization, Parameters) on the PLAT! Those areas where Survey Plats are not required (or can't be easily recorded), are going to pose some additional problems in that regard, but that's life.
The last couple of years have been somewhat of an eye opener for me, in that I have found myself in the perilous position of having to deal with many Survey Plats filed for record in Utah. Some of these are very good, but most are the result of undocumented ÛÏcalibration/localizationÛ Charlie Foxtrots, that defy any sort of rational explanation from a spatial standpoint. If (sometimes big IF) you can find enough monuments to get ÛÏon toÛ their bearing and scale, you can usually generate a formal projection that fits pretty well, but I suspect that too many ÛÏcrewsÛ (or office folks) NEVER even look at the ÛÏcalibrationÛ residuals before ASSUMING that all is well.
BEEP, BEEP, dump into CAD, connect the dots, Print, File, Invoice, Next Project!
I'd a lot rather see decent metadata (projection parameters) on every project, than the Alphabet Soup (Add, Subtract, Multiply, Divide) "modification" of a canned Coordinate System that obviously DIDN'T FIT the Project in the first place!
Oh well, I got off track there somewhere (and get off my lawn!)
B-)
Loyal
Loyal, those are interesting comments. Here in North Carolina, elevations range from sea level to something over 6,000 feet. In Arizona back in the early 90s, our desert guide referred to those "hills that you call mountains back East." To me, it was an eye-opener to discover that my son's house in Kansas has an elevation of about 1,000 feet higher than mine in North Carolina. Kansas is supposed to be flat, right? But elevations change rather quickly on the West side of the Mississippi.
So, what works well in NC is not so good in UT. What works well in UT would also work well in NC, but the gains would not be as significant. But the math is fascinating in both states.
I think a lot of guys misunderstand coordinates and complain about a "shift" in modified coordinates. State Plane coordinates are a defined system with an specified origin. Apply a combined factor is to just get a distance that reflects surface distances. Getting used to that fact, it doesn't matter what the origin of you project coordinates are....the only reason it might matter if if you have State Plane "look-alike' coordinates. But reading the explanation is more important. You need to know what you got. If you publish the "metadata" on how to get from your local project coordinates to State Plane is so that someone can follow in your footsteps and/or realize the geodetic coordinates if they need them.
Tom Adams, post: 356960, member: 7285 wrote: I think a lot of guys misunderstand coordinates and complain about a "shift" in modified coordinates. State Plane coordinates are a defined system with an specified origin. Apply a combined factor is to just get a distance that reflects surface distances. Getting used to that fact, it doesn't matter what the origin of you project coordinates are....the only reason it might matter if if you have State Plane "look-alike' coordinates. But reading the explanation is more important. You need to know what you got. If you publish the "metadata" on how to get from your local project coordinates to State Plane is so that someone can follow in your footsteps and/or realize the geodetic coordinates if they need them.
That's the KEY Tom!
Unfortunately, the "metadata" (how he done it) is often missing, and even when it IS there, it doesn't always WORK.
A properly defined LDP is one button away from Lat/Lon OR SPC/UTM, without all of Alphabet Soup manipulations of the Project Coordinates (which all too often LOOK like SPC/UTM coordinates[but are not]).
Loyal
Adam, post: 356951, member: 8900 wrote: I never said that I didn't know what Javad is doing with the numbers, although there are others who are better suited to explain it. All coordinates in the LS are stored in Lat long and height, then projected to whatever projection is needed. For localization the coordinates are still internally stored as lat long.
Ok, then what are they doing with the numbers, what is the coordinate system of these 500000 numbers based on?
And do the elevations shift to the correct numbers, or are they fixed with the ZY?
Moe, I am confused to your question because every point collected is stored in the database as ITFR 08, you can convert to any known state plane coordinate system, LDP, or unknown off the wall rotated to grandma's front porch and the line of sight passing the barn to the other corner, coordinate system you want. All points are stored internally as ITFR 08. I took nates page 1 as being a localization page where 50000 numbers are arbitrary but Nate may be using that as an almost state plane page, I dont know what Arkansas state plane cooordinates look like so forgive me if that is so.
Now just a minute. I know what it is doing. It is exactly what I want it to do. Moe, When the dust settles, I know:
1.) SPC for EVERY point.
2.) I can input SPC and work with it. Any SPC point I input, can be worked with, and expressed in a local system, simply by changing pages.
3.) I know the metadata for any point I want. Including Theta.
4.) I also have a local system, set up, so total station values are easy to work with.
5.) It is a good system.
Nate
Loyal, the most elevation change I have ever seen on one of my projects was around 1000' maybe 2000' and I have worked on Beach Mountain which is a mile high town in NC. I love the West and have close friends in the Rockies. I have been to Burns Colorado and Casper Wyoming and there is no doubt ya'll got your work cut out for you when it comes to surveying. Hats off to you guys.
Adam, post: 356968, member: 8900 wrote: Moe, I am confused to your question because every point collected is stored in the database as ITFR 08, you can convert to any known state plane coordinate system, LDP, or unknown off the wall rotated to grandma's front porch and the line of sight passing the barn to the other corner, coordinate system you want. All points are stored internally as ITFR 08. I took nates page 1 as being a localization page where 50000 numbers are arbitrary but Nate may be using that as an almost state plane page, I dont know what Arkansas state plane cooordinates look like so forgive me if that is so.
The question I have and no one seems to be able to answer is this:
You are using coordinates for your local system, the system you do your drawings and projects on, what is it?
It's not state plane, it's not ITFR, what is the projection?
How is it created, how does it work
Moe,
It is ground coords. Local coords. However, these local coords, in the Javad LS, are sitting on top of true SPC. I can export the Underlying SPC, any time after dpos. Or, import true SPC.
It's just one of many flow charts.
I can export SPC, scale them, and assign some point an arbitrary smaller local value, and achieve the same results.
To send coords back to the LS, I'd have to scale, and translate them back to SPC, and then they would go back in. However, this whole process, is automated, when set up properly, in the LS.
It's the same apple, just looked at from a different angle. I can export pure SPC, at any time. The underlying coords are SPC, of your choice.
It's native coord system is lat lon, and all things inside are tied to that native coord system. One exception. When you bring in coords, of an unknown datum. These are "floating in space" until they are tied down, to their actual lat lon.
I
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MightyMoe, post: 356977, member: 700 wrote: The question I have and no one seems to be able to answer is this:
You are using coordinates for your local system, the system you do your drawings and projects on, what is it?
It's not state plane, it's not ITFR, what is the projection?
How is it created, how does it work
I do all my projects and drawings on Nad 83 2011 zone 3200 bearings and ground distances, The only time I use localization is when I have a deed with no coordinate system or I am orienting to someone else's control for construction. When I localize to the points with no coordinate system they are in reality available for use in my state plane system. I personally dont like having my drawing on some random coordinate but prefer it on state plane bearings and distances or scaled distances depending on the size of the project, so I can insert aerial photos and other georeferenced materials.
I tell you what, I luv everyone of ya'll and much appreciate what all I get from this site. I have learned things from folks there is really not a chance of me ever communicating with in this life except on this forum. I can pinch and grab at little bits of info that will make my life easier from the other end of the globe and I can scratch my head a bunch about why things are done different. But here, there's a lot a learning to gain.
I tell you what, I luv everyone of ya'll and much appreciate what all I get from this site. I have learned things from folks there is really not a chance of me ever communicating with in this life except on this forum. I can pinch and grab at little bits of info that will make my life easier from the other end of the globe and I can scratch my head a bunch about why things are done different. But here, there's a lot a learning to gain.
The LS let's you set up one page on true spc. Then, you have some 10 more pages, to set up on whatever datum you like.
Think of it as a 10 Local systems, sitting on top of true spc, with a 7 parameter translation, to get from spc, to each of those local systems. Just change pages, and you are on that local system. Since the LS is only using one core coord system, lat lon, then making one of these local systems is just a "7 parameter window", that you look at the Underlying SPC through.
It's the bomb!
Adam, post: 356981, member: 8900 wrote: I do all my projects and drawings on Nad 83 2011 zone 3200 bearings and ground distances, The only time I use localization is when I have a deed with no coordinate system or I am orienting to someone else's control for construction. When I localize to the points with no coordinate system they are in reality available for use in my state plane system. I personally dont like having my drawing on some random coordinate but prefer it on state plane bearings and distances or scaled distances depending on the size of the project, so I can insert aerial photos and other georeferenced materials.
That makes perfect sense to me, I do much of my work the same way.
And I hate to harp on this, but back in the day Trimble had a procedure where you did basically what Javad is describing.
Set on a point, give it a coordinate and it would preform a "Plane Projection" around that point.
About 98-99 they stopped supporting the "Plane Projection" for a number of reasons.
It was a bad idea, as you carry the "Plane Projection" for any distance it fell apart.
From then on if you want to do something like that with Trimble it needed to be a Transverse Mercator projection.
So if you set on a point and give it a coordinate it becomes a Transverse Mercator projection with a well defined origin lat, long, origin northing, easting, bla, bla, bla
You can print out all the parameters on a couple of sheets and you have a well defined LDP and all the metadata you can stand.
My question is what are these local coordinates, are they some kind of Transverse Mercator system with well defined metadata that can be applied to recreate them? And then when the base point is changed and the coordinates don't change is the new system created as a new TM projection with the origin point moved or is it the same TM projection with a datum transformation, all this is very important to know, and what happens with elevations?
If, it is doing a datum transformation and holding the "original" TM projection that is important. It would be different than shifting the TM parameters to match the new Lat, Long, and all this should be available in Javads software to see. Often I think salesmen send out this stuff without really explaining what is going on. However, this is very important metadata info that should be available and always looked at.
I much prefer picking my parameters ahead of time, then sticking with them, I'm sure Javad easily supports doing that.
Nate The Surveyor, post: 356985, member: 291 wrote: The LS let's you set up one page on true spc. Then, you have some 10 more pages, to set up on whatever datum you like.
Think of it as a 10 Local systems, sitting on top of true spc, with a 7 parameter translation, to get from spc, to each of those local systems. Just change pages, and you are on that local system. Since the LS is only using one core coord system, lat lon, then making one of these local systems is just a "7 parameter window", that you look at the Underlying SPC through.
It's the bomb!
Nate, I beg to differ a little bit about that.
They aren't translating from SPC to a local system, it's not looking at SPC at all.
They are projections from Lats, and Longs to whatever the XY system is, SPC is completely irrelevant to those coordinates.
There needs to be some rules that create these local coordinates, my point being what are they and why do they hold the coordinate on a point once that lat long is figured out, and what happens to the elevations?
The local system is NOT a re projection. The LS allows a little "fake", local coord system to be built off the actual SPC.
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Nate The Surveyor, post: 356990, member: 291 wrote: The local system is NOT a re projection. The LS allows a little "fake", local coord system to be built off the actual SPC.
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How does it do that?
I'm not sure what you mean... It does keep the elevations, and it does the same things we would do manually, but it does it in an automated way...
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