Nate The Surveyor, post: 356995, member: 291 wrote: 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...
Sent from my VS880PP using Tapatalk
Nate, it's a modified state plane,,,,,,I'm guessing,,,,,a simple subtraction from the spc number to the one you give,,,,then it calculates an adjustment factor and applies it somewhere, at your base or 0,0
At your scale base coord, I believe.
Sent from my VS880PP using Tapatalk
Got it, thanks nate
It can do a simple subtraction of northings. And a subtraction of eastings. And a simple scale. And a simple rotate. And a simple EW tilt. And a simple NS tilt. To make or fit this local system.
Thus, it can work on a localized system, based on local level runs, and uneven gravity.
Sent from my VS880PP using Tapatalk
Moe, I'd like to set my LS up out behind the house here and give you a link to where you can control it from your desktop if you would like. You can put any Coord sys or ldp u like and play around with it.
Nate The Surveyor, post: 356999, member: 291 wrote: It can do a simple subtraction of northings. And a subtraction of eastings. And a simple scale. And a simple rotate. And a simple EW tilt. And a simple NS tilt. To make or fit this local system.
Thus, it can work on a localized system, based on local level runs, and uneven gravity.Sent from my VS880PP using Tapatalk
Nate, they all do those things
Yes.
Sent from my VS880PP using Tapatalk
You can go to the Javad website and select.road show and control an LS from your computer as well. Feel free to put in any parameters you like. Keep in mind the receiver is probably not located in your state.
Adam, post: 357001, member: 8900 wrote: Moe, I'd like to set my LS up out behind the house here and give you a link to where you can control it from your desktop if you would like. You can put any Coord sys or ldp u like and play around with it.
That's sounds interesting adam, but I understand what Nate is doing now, the projection is state plane with a scale at the base, it's what we all have been doing for decade's,,,,,,there is no local projection or
"local coordinates" but modified state plane
coordinates.
So...let me get this straight Nate, Ya'll go out and push this here button, then that button, then scroll to Page 1 and enter some arbitrary N/E values, push another button, Calc some stuff in your laptop, then stake some stuff out. Then ya go home, connect to something, get a new set of numbers, scroll to another Page, then push a button, then scroll back to another Page, then dump some numbers into CAD, and create a PLAT. The Plat has metadata that says:
Go to Page 0 to see where I are in relation to the real world!
Got it!
That makes a lot more sense than just publishing NAD83 Projection parameters.
Bottom line... it doesn't sound like YOU really KNOW what the hell is going on behind the curtain, and neither will the next guy who tries to follow your work.
Just saying...
:angel:
Loyal
In Javad's software, and this is true for most, but not at all, you have several choices for projections. In all cases for Javad, the points are stored in the database as Latitude, Longitude and Ellipsoid Height in ITRF 2008, epoch 2005. By way of HTDP built into the software, these ITRF positions can be expressed as NAD83(2011) positions, epoch 2010. Most users will not see this however as most will opt for a projection. The projections make use of HTDP to obtain geodectic coordinates in NAD83 that are then projected into the grid system. The projection options are:
- Use standard well known projections from library. This would include State Plane, UTM, several county wide LDP systems that are published and a few State wide systems not connected to State Plane. When starting with an autonomous base position, the user collects points, then can process the base data through DPOS automatically and allow the software to translate the rover points based on applying the vector from base to rover to the newly solved base position. All of the surveyed coordinates will change by whatever translation there was from the autonomous base position to the DPOS base position. Users can do this manually with OPUS also, but DPOS offers a lot more convenience.
- Use a LDP. I have several loaded in the LS that I use daily. I use them more often than State Plane. The LS software (J-Field) supports several different projection types. Most of mine are Transverse Mercator. DPOS operates the same way with an LDP as it does for a published projection in the library. Coordinates will shift by the same amount as the base shift from autonomous to DPOS if a DPOS adjustment is performed. I like LDP because I can have all coordinates in an entire county on the same system and the inverse between these coordinates will very nearly approximate a ground inverse with no need to apply a scale factor. (LDP has been exhaustively discussed elsewhere).
- Use a localization (or calibration for Trimble users). A localization is a set of instructions to transform coordinates in a projection. This transformation will usually include options for 7 parameters: translate N, E, U (North, East, Up), rotation around each axis, N, E and U, and Scale. In Javad's software these can be solved by Helmert Transformation or can be entered manually. The localization MUST have an underlying projection. This is because the localization is simply a transformation (or set of instructions) and must have a base projection to which the transformation will be applied. Often a surveyor will select State Plane as his underlying projection. Javad actually allows users to select a geographic system (latitude and longitude) to create a localization upon. I believe Trimble does this as well. I'm not familiar with Leica or Topcon. Carlson does not allow a localization to be created from a geographic system that I am aware of. For Trimble and for Javad, the software still doesn't actually perform the localization from the geographic positions, but creates a projection on the fly, and projects the geographic coordinates onto the new projection, then performs the Helmert Transformation from these grid coordinates. Javad uses an Oblique Stereographic, and I believe Trimble uses an Oblique Transverse Mercator. For the smallish sites generally used for localizations, there is not a functional difference between them and most will not use this technique anyway, but will use a standard projection. DPOS behaves differently with a localization for reasons I will explain below.
A localization and a LDP vary in some significant ways. A LDP is a projection. Each grid coordinate equals a unique geographic coordinate on the Earth (within the valid range of the projection type). A localization grid coordinate is equal to a point (not a coordinate value) on the Earth that has an underlying projection coordinate that has a unique geographic coordinate. Typically a localization is developed because a particular object on the ground has an assigned coordinate. Perhaps a control point has an assigned local grid coordinate of N 5000, E 5000. This point will always have this coordinate. However, in a projection, this control point may have a coordinate today of N 1,234,567.89 E 9,876,543.21. Tomorrow we observe it again and the coordinate is N 1,234,567.92 and E 9,876,543.18. The point hasn't moved, the measurement is simply different, but from a purely mathematical sense, the projection coordinate has moved by +0.03 and -0.03. For the localization the coordinate is still N 5000, E 5000. So if we start our base with an autonomous coordinate and perform our localization (for simplicity let's say that it's a single point localization) our localization point has a Geographic Coordinate 40å¡N and 100å¡W and it has a projection coordinate of N 1,234,576.54 and E 9,876,545.67, Anywhere Plane System, 2011, and we've assigned a localization coordinate of N 5000 E 5000. Our localization would look like this:
Underlying System: Anywhere Plane System, 2011
Unit: US Survey Feet
North Origin: 1,234,576.54
East Origin: 9,876,545.67
North Ground: 5,000.00
East Ground: 5,000.00
Rotation: 0å¡00'00"
Scale: 1.0000 0000
Tilt North: 0å¡00'00"
Tilt East: 0å¡00'00"
Vertical Translation: 0
Now a smart roller is going to figure up what the combined factor for this origin point is in the Anywhere Plane System of 2011. Maybe it's 1.000123, for example. In that case, he should manually enter that or perhaps the software loads it for him. Either way, this should be accounted for. This would allow him to have his coordinates roughly scaled to ground. Or better said, it would scale his coordinates roughly to that particular elevation. Now the localization projection surface is actually the same as Anywhere Plane System. It's not likely that the Anywhere Plane System is parallel with the ellipsoid where this job is, so the grid factor is not going to be consistent for long distances. The plane is either diverging from the ellipsoid or it is converging. But it probably isn't consistently offset. It okay as long as the localization is for a small area. But the "ground" coordinates will cease to represent the ground with severe changed is a change in elevation (terrain) or severe differences in the distance between the grid and the ellipsoid. The smart roller will also know what the underlying system is so that he will know what North is for his localization. If it's a new projection on site, North will be geodetic(ish). If the underlying system is State Plane, North will be Grid North.
So in this example, the horizontal translation between the two systems is N -1,229,576.54 and E -9,871,545.67. But this was based on an autonomous position of the Anywhere Plane System origin. What happens if our intrepid user decides to correct this autonomous position by post processing using DPOS (or OPUS for non-Javad users). Now the origin comes back from DPOS (or OPUS) as 1,234,567.89 and 9,876,543.21. This is a translation of -8.65 and -2.46 feet. So our surveyor that wanted a clean 5000, 5000 for his physical point now has a localized coordinate of N 4991.35 and E 4997.54. To rectify this, Javad will automatically recompute the localization, shifting the Anywhere Plane System coordinate according to the post processing result, but leaving the local coordinate at 5000, 5000. This is simple enough, changing the translation ever so slightly in the localization parameters. This is key. Don't miss this. The coordinates are all in Latitude, Longitude and Ellipsoid Height in the database. Projections and localizations are lenses for view these geographic coordinates. We can change lenses and things look different even though the thing itself is unchanged. The geographic coordinates make one movement, from autonomous base position to DPOS (OPUS) base position. (In truth, this translation is XYZ ECEF, but the coordinates are stored as LLH) Because the projection coordinates are directly tied to the geographic coordinates, they translate as well. They must. One grid coordinate equals exactly one geographic place on Earth. The localization however isn't tied in the same way. For a localization, a local coordinate is attached to a point. The point didn't move when we post processed the base. It's still in the same place: 5000, 5000. The geographic position changed. The projection coordinate changed. The local coordinate did not. So we redefine the translation parameters between the projection and the local system to accommodate the change to the projection coordinates. So now our translation is N -1,229,567.89 and E - 9,871,543.21. If we look at our surveyed points with a projection "lens" we see projection coordinates. If we look at the coordinates with a local "lens" we see local coordinates. But the coordinates themselves do not change. The lat/long remains the same.
This is somewhat simplified. Changing the projection coordinates slightly, as we have here changes the distortions slightly. But that's for a different discussion.
Loyal, it is not a problem to put spc metadata on the plat.
Nate The Surveyor, post: 357020, member: 291 wrote: Loyal, it is not a problem to put spc metadata on the plat.
Of course NOT...BUT you were talking about some kind of 5k/5k thingamajig!
Now whether or not (or HOW) THAT set of "Page 1" (or was it Page2) coordinates relate to "true" SPC, was somewhat unclear (to me anyway).
Maybe I just misunderstood your explanation (wouldn't be the first time).
:-$
Loyal
Ok, I'll try again. (i didn't get it 1st time around either)
We have multiple things going on at once.
We have NAD 83 projected to Arkansas South. Spc.this is Set on page 0. This becomes our core datum.
This then becomes our window, through which we view NAD83. It is a plane, and is our core system of addressing NAD83.
Now, we go to page 1. It is a ground local system. It is scaled to ground, it has smaller coord values. This now is our window, through which we view Arkansas South. SPC If you change elevation too much, or travel too far, you begin to see distortion.
But it works good for a small area.
So, to summarize:
We are using a local system, on page 1, to look at a state plane system (Arkansas south), which is on page 0, which is our state plane system, which we are using to address NAD83, which is our core coordinate system.
Got it?
Since our core coords, are NAD83, we can set it up, at our pleasure, with Arkansas North, on another page, and then build another Ground system based on that, if we so desire. Or it can be expressed as Texas North. Whatever we decide, based on our needs. Or our client's needs.
Loyal, this is my attempt to express the practical things I have learned to work with in the last few years. I'm sure I'll be better at explaining it next year.
All of this coming from a guy who didn't even want to hear about spc, 20 yrs ago. Now, they are part of my life.
The use of pages 0 to 10, are tools, through which we can view or express data, in differing formats. They are just tools. Data view ports. There are other uses for these pages, but we wo,t clutter up this discussion with more information, at this time.
Seems the simple definition of the localization is that it is a tangent plane system connected to SPC at only the localized point?
Because tds does not allow this versatility, the confusion surrounding this discussion is understandable.
The "point of understanding" for one fellow was the awareness that Page 0 stays spc. For me, that would be usually Arkansas South Zone, projected from nad83. But, it can be whatever you assign it to be., for where you work. With the one modification of this data, from autonomous, to corrected, or adjusted spc, via dpos.
These are convenience tools, that accomplish many things at once.
Forgive my attempts to explain new tools, in my language.
I'm wondering if a data collector can be made that only uses nad83, exclusively? Possibly eventually. Until then, these are tools, in the surveyors toolbox.
Scott Zelenak, post: 357030, member: 327 wrote: Seems the simple definition of the localization is that it is a tangent plane system connected to SPC at only the localized point?
Not really. A localization can be based on a tangent projection (stereographic). But in Nate's case, the localization utilizes a State Plane Coordinate System. A localization can be thought of as a table of the 7 parameters of a 3D affine transformation. (An affine transformation is a transformation in which the shape of a thing is maintained - straight lines are straight, parallel lines remain parallel, interior angles remain the same). The localization carries all of the same distortion as the underlying grid system.
This is not the case for comparing State Plane and an LDP, except in the case of perhaps of Loyal's use of LDP design to replace modified State Plane Systems. In most cases the projection type is different and the geographic origin is different. This means that the rates of change for distortion is different. So there isn't an affine transformation between LDP and State Plane. Over small areas the transformation can be treated as affine because the difference is negligible.
If the localization carries all the distortions of the SPC system how can it be affine?
I grasp the LDP concept but the lightbulb over my head isn't lighting up for the affine localization.
I need some coffee...
I suppose a user could create localization Metadata. Before we started using LDPs, we were basically using affine transformations of SPC to deliver ground coordinates rotated to geodetic North at some arbitrary point in the survey. In our Metadata we stated that bearings were related to geodetic North, rotate by x to get state plane grid. Distances are horizontal at the surface, multiply by csf to get grid distance. That's two of the 4 parameters for a 2D transformation. All that was left was the translation in North and East. We never published the local coordinates, only the State Plane, so this was unnecessary. But we could have added that 5k, 5k equals SPC N, E, and then published local coordinates all over the drawing.
