OK, so let's replace the nail in pavement with NGS mark EZ4026. If I set the GNSS over that mark, I want it to give me the superseded coordinates below:
EZ4026 NAD 83(2007)- 35 59 49.32944(N) 079 54 47.97618(W) AD(2002.00) 0
You type it in, you're the one in control.
Well yes. If I set up a base on ol' EZ4026, then I want the rover to believe that the coordinates of that point are the NAD83(2007) coordinates, so I punch in that Lat/Lon. Then 'm on NAD83(2007) coordinates.
But I can't just type in NAD83(2007) and have the machine record correct coordinates.
Well yes. If I set up a base on ol' EZ4026, then I want the rover to believe that the coordinates of that point are the NAD83(2007) coordinates, so I punch in that Lat/Lon. Then 'm on NAD83(2007) coordinates.
But I can't just type in NAD83(2007) and have the machine record correct coordinates.
I'm confused, do you want the machine to type in the coordinates for you?
Translations from one realization of NAD83 to another are always rubber-sheet type affairs - not something I'm interested in from a surveying perspective. I suppose that it has some value to GIS people.
THE BLUE BUTTON IS BACK!!!
@bill93 you about nailed this. The GPS satellites don’t truly know about wgs84 they are in there own system each satellite only cares about center of the earth gravitational position within reason. Wgs84 is actually created via the satellite GPS and some other systems and models. The satellite’s system is a coordinate system always changing. We would not have wgs84 as we know it without the satellites themselves and the monitoring stations. We actually let the satellites tell us where they are then we tell them where they were. Its an endless cycle. Lol. I believe it was wgs72. Dave help me with that. Which was created as a world wide system prior to gps as we know it now. Also we need to be careful that gps. Wgs84 are ONE and gnss is a totally different animal all the other satellites systems. So other systems can be used in conjunction with what we do on nad83 or any other datum. But we don’t need them in order to be used for TRUE wgs84. However they are all working closely to be used effectively together. I believe the op can simply do his rtk like he has been with his here position but log data to send to opus and then update that so every thing moves to datum. In his tsc3 choose nad83 and whatever state plane zone with the base results being updated it has essentially moved to nad83/2011 because the nad83 datum has not changed just the realization has and at a epoch of time. He will be so close within the measurement uncertainty he is good to go. Of course it is better to stay updated with software. But much more important is the firmware in the receiver itself in my opinion. This keeps gps and tech note changes up to date. And correctly listening to codes messages from the satellite themselves.
Moe, with all due respect, please do not ever try to mentor someone. I love you and I respect you more than you'll ever know, but don't mentor. I'm just trying to, using your terminology, "get on" a coordinate system.
No confusion, just tell me step by step how I do that.
@mathteacher on gps.gov. You should be able to pull the latest tech mote document that manufacturers should use as a guide for all messages codes and signals that the gps satellite broadcasts and how to use them. Now thats what is for public release. And not every manufacturer follows that guidelines to the T. They figure out other ways to do things. But thats what they were intended for. Tech note 36 was one of the latest big significant changes which on the public side was very thoroughly attended and tracked meetings for a while as it was being defined etc. lots of very intelligent people from manufacturers scientists in the pnt environment and such that had a presence during that change. Of coffee there is that side of the house and then another side that is not for the publics need to know.
Moe, with all due respect, please do not ever try to mentor someone. I love you and I respect you more than you'll ever know, but don't mentor. I'm just trying to, using your terminology, "get on" a coordinate system.
No confusion, just tell me step by step how I do that.
You set on the known point with your base receiver. You tell that receiver what the coordinates are and you broadcast to the rover so the rover knows where it is.
That's a base/rover configuration, if there are broadcasting base's nearby from a service such as a CORS point or an RTN system then you pick up those broadcasts to figure out where your receiver is.
But, no matter which system you use you have to be in control. You have to set-up the system you want, then you have to connect your receiver to the base station you set on the 2007 point with the coordinates you gave it or a service provider. If it's a service provider you need to know what flavor of coordinates they are broadcasting.
Basically there is a disconnect between what a single receiver can do. It really can't "get itself" on any accurate position. There are huge improvements from the early days, but if you really want to have coordinates accurate enough to distinguish them from ITRF and NAD83 then you have to connect with known points, that's true for RTK and PPK. Trimble has a service you pay for called RTX that "gets you on" but it's the same principle, there are base stations broadcasting to position the rover. I don't use it, but I have colleagues that say it's really good.
I'd double-like this and many others if I could. Too many to mention; I'd leave somebody out, but everybody who replied or commented on my questions, THANK YOU! And a huge amount of consistency!
I can do a lot of math, some of which I actually understand, but using those models on the actual ground is what I'm mainly clueless about.
Thanks for the understanding.
No confusion, just tell me step by step how I do that.
In order to establish control in a certain realization of NAD83 you need to begin your measuring at some point for which coordinates are known in that realization.
If the realization you want is 83(2011) one way to do that is to set your base up and collect data to send in to OPUS. OPUS will return a value for the base in 83(2011). Alternatively, you can set up over some passive mark for which 83(2011) values are known.
If you want to work in some earlier realization you will have to find some monuments for which values in that earlier realization are known. NGS Datasheets frequently include "superceded values" for monuments, including CORS stations, which are values for legacy realizations. If you have the resources to compute static vectors you could download CORS data, combine it with base station static data, and compute a vector. Then use that vector data and the legacy realization position to compute new positions in the legacy realization.
So you have to go back to source and make measurements. There is no other way that is not an approximation. There is no direct mathematical relationship between one realization and any other.
@mightymoe you can do PPP precise point positioning or absolute positioning and use a single receiver and get on whatever datum you prefer. Not utilized a lot YET on our side of the house Land Surveying side it would not be a cost effective way to survey. To time consuming. But i am not much on making prophecy but If i were i would say we are not far at all from doing this in a near realtime type environment. The amount of processing power we have in such small devices these days along with the extra constellations I might live to see this. When I first started doing PPP was in the 2000-2005 years. We collected 2 24 hour sessions by the time i left and a few years later we could get better accuracy in just 2 4 hours worth of data. This was GPS only. Now a bit different math than solving vectors but what i can say it might just blow your mind at what can be achieved.
However this was not to argue with you but just to make you aware if you were not. Also one of the things we all should be thinking on and how we all will deal with the fact when the new datum is released is all those monuments for us to get on and fix to a datum will not be the primary. The CORS backbone will. So Active vs passive control is terminology that has been used. NGS will not be maintaining the monuments. I will be one when possible and feasible to use them just so much history but the datum will not be from sitting on that monument it will be from the primary CORS that NGS states for us. How this will effect the profession is still somewhat unclear. There are still many many surveyors who do not use gps or gnss at all. I have set control for them when required for the recordation in certain ares of a plat and have spc on it. So only having access through gnss to the new datum and that history we have of that monument or monuments is a concept that is talked about frequently in my area. I mean even those with gps often check at minimum to a monument in the NGS database.
So probably something worth mentioning as I was asked this question just the other day. For some reason a person asked about the difference in doing transformations in NCAT. Vs NADCON and VERTCON. No difference just ncat is the front end user interface to both of these tools. I hope i am stating this correctly. Also whenever you do a transformation say nad83 2011 to nad 83 harn example. Or to nad 27. Etc navd 88 to ngvd 29. It gives you estimates on how well it thinks the transformation is. I have found several times that my error in physically measuring a monument in my small piece of the world to be fairly good and fall withen the error ellipse it states. Now i have seen outliers. Was it the transformation that was not good or has the monument moved settled etc.
Time for confession. I've used the same NAD83 datum selection on my field software whilst surveying as I used 20 years ago. Even though the coordinates may get updated on control and reference stations our checks have been fine regardless of what realization it is. You just need to know what realization your coordinates are for record keeping and for not mixing various realizations. I never could understand the need for so many choices of NAD 83 on the field software side. I think the customers freaked every time control coordinates were updated and the vendors went along with it. Essentially all they do is copy the old parameters and rename it to the new name being used. The NAD 83 cage built of lines of latitude and longitude has the same definition as always. The earth and the control points move around inside the cage thus updated coordinates are realized. It doesn't mean you need a new NAD83 configuration in your survey field software.
