Jeez! Now we need 4-dimensional coordinate systems??!?!? I was just getting used to 3! :p
This will be an issue here as well. The new horizontal datum will probably be aligned with the ITRF on a certain date, say 1/1/2022 (not sure if this has been decided definitively yet). After that date, we will slowly drift way from ITRF if we use a static datum like we have been using. However, if we use a dynamic datum, that will create its own set of problems. For example, I do a lot of deformation surveys, we compare coordinates epoch to epoch to detect movement. But, if the coordinate system is moving, we must remove that from the coordinates to detect movement.
Not an easy issue to resolve (static versus dynamic), but as autonomous GNSS becomes more accurate and precise, this will be a big issue. I would realistically estimate we will soon (several years) have autonomous accuracy on cell phones of 0.1 meters. That is only a few years of movement of the NA plate.
John Hamilton, post: 383261, member: 640 wrote: This will be an issue here as well. The new horizontal datum will probably be aligned with the ITRF on a certain date, say 1/1/2022 (not sure if this has been decided definitively yet). After that date, we will slowly drift way from ITRF if we use a static datum like we have been using. However, if we use a dynamic datum, that will create its own set of problems. For example, I do a lot of deformation surveys, we compare coordinates epoch to epoch to detect movement. But, if the coordinate system is moving, we must remove that from the coordinates to detect movement.
Not an easy issue to resolve (static versus dynamic), but as autonomous GNSS becomes more accurate and precise, this will be a big issue. I would realistically estimate we will soon (several years) have autonomous accuracy on cell phones of 0.1 meters. That is only a few years of movement of the NA plate.
That's an interesting thought. Wouldn't it be moving by the same amount that the overall reference frame in the static system would be drifting by anyway? Would it be noticeable?
What I mean is, if you are monitoring the deformation using GPS, then the actual latitude and longitude values would be moving anyway due to continental drift.
I would be surprised if NGS changes their philosophy of maintaining a datum linked to the North American Plate. They will probably continue providing both IRTF and NAD(xxxx) in OPUS reports. Other software does and can continue doing so. Somebody has to do it in order to go back to where you were on a previous date, and it makes more sense to maintain the present work flow.
The real problem will be that the numbers are so close between systems that many people will be confused by which they have due to carelessness with metadata.
Dan Patterson, post: 383274, member: 1179 wrote: That's an interesting thought. Wouldn't it be moving by the same amount that the overall reference frame in the static system would be drifting by anyway? Would it be noticeable?
What I mean is, if you are monitoring the deformation using GPS, then the actual latitude and longitude values would be moving anyway due to continental drift.
To detect movement over time I need to compare coordinates at different epochs. If the coordinate system is moving as well, that introduces another level of complexity. What I will probably do is create local coordinate systems at each project (there are 39) and keep fixed coordinates there. The "origin" at each project will have a constantly changing ITRF coordinate, albeit slow and predictable, but the local coordinate of that "origin" will remain the same.
John Hamilton, post: 383284, member: 640 wrote: To detect movement over time I need to compare coordinates at different epochs. If the coordinate system is moving as well, that introduces another level of complexity. What I will probably do is create local coordinate systems at each project (there are 39) and keep fixed coordinates there. The "origin" at each project will have a constantly changing ITRF coordinate, albeit slow and predictable, but the local coordinate of that "origin" will remain the same.
But that's not how you do it now? I would think that's kind of how you've been doing it all along. If the whole site moves it's no big deal, but if the bridge or dam or tank or whatever it is moves relative to fixed points at the site, then it's a problem.
I'm just trying to understand what the difference will be. I've never used GPS to monitor anything before. Maybe for the initial site control, but after that we used differential leveling and total stations.
I hope I'm retired when the new datum comes out, I already have enough problems with trying to compare surveys done last week with surveys done in NAD83(NSRS2007)/Geoid03 to model beach erosion or the like.
We're moving over 4cm/year over here on the West coast. Isn't this movement what we already take account of via the Epoch date and the NGS HTDP utility?
Bill93, post: 383280, member: 87 wrote: I would be surprised if NGS changes their philosophy of maintaining a datum linked to the North American Plate.
NGS will be replacing NAD 83 and NAVD 88 in 2022:
http://www.geodesy.noaa.gov/datums/newdatums/index.shtml
from http://www.geodesy.noaa.gov/datums/newdatums/WhatToExpect.shtml
Other changes regarding how you access the new datums and transform existing data will await decisions to address challenging technical issues including:
- Adopting a USA-specific reference frame with Ûplate- fixed coordinatesÛ or ÛÏtemporal coordinatesÛ using International Terrestrial Reference Frame (ITRF) coordinates and velocities.
So it seems they are evaluating both approaches. Either way, you or they will have to apply the time-dependent transformation so that coordinates can be related by measurements taken at different dates.
What I find hard to believe is that Kent doesn't actually figure in plate tectonics with his supercalifragibodacious vector analysis when determining where monuments REALLY are...
With an average drift of the NA continent of .7cm to 1.5cm per year, he probably has to spend a week per year repunching divots in the tops of all his monuments. 🙁
This is an interesting issue. I'm not worried for myself as surveyors who deal with small parcels of data wont be affected that much, however I believe the entire decision making process by ISCM ( http://www.icsm.gov.au/index.html ) was flawed.
The main driver of the issue in Australia is that they powers that be think that by 2020 everyone will have a mobile phone that will give them accurate 0.5m coordinates. Then the 1.8m shift will become apparent to everyone, not just surveyors.
See here for full documents ( http://www.icsm.gov.au/geodesy/modern.html ) and ( http://www.icsm.gov.au/gda2020/index.html ).
From that site with my comments in red.
The major trends identified by the PCG include:
- The fully operational and enhanced global and regional satellite navigation constellations including Galileo (Europe), GPS (USA), GLONASS (Russia), Beidou (China), QZSS (Japan) and IRNSS (India) that will enable affordable consumer grade GNSS positioning to better than 50 cm accuracy and augmented positioning to better than 3 cm accuracy in realÛÒtime. The issue here is that they are talking about each of the millions of users as if they are individual. Instead it should be remembered that all of these users will be using only a few thousand apps. Why not write the conversion software for ios, android, etc and distribute it freely?
- A growing economic dependence on highly accurate positioning to underpin efficient transportation, spatially enabled business and government, and industrial automation (e.g., robotic mining and precision agriculture). The two best examples of the growing economic dependence are listed as robotic mining and precision agriculture. Robotic mining would be using a mine site datum and/or base station which moves with Australia. Precision ag is the same. If they use a CORS or have their own base, the moving Australian plate has no affect on them.
- A growing reliance on spatially enabled business processes that in turn utilise machine to machine (M2M) communication of highÛÒaccuracy positions and high resolution geospatial data in real time and three dimensions. This can happen regardless whether the current coordinate system or new one is used.
- Globalisation of coordinate and geodetic frameworks as a result of increased global services, the development and widespread adoption of nonÛÒAustralian consumer (nonÛÒenterprise) geospatial applications. See the first red comment.
- Many users including those in the transportation sectors (aviation, maritime and road) operate within globalised frameworks that are constrained by requirements that limit the support of individual national datum and have a necessity to conform to international standards. There are different laws and regulations in every country (and lots of differences within countries too) of the world and now apparently Australia is not allowed to be different on this issue??
It has been demonstrated that most people care about relative position, not coordinates. All they want to know is how far they are away from something, not the exact lat long (or utm or ?) coords. Why stuff around with the background numbers then?
The people most affected by this are the municipal authorities, service owners, etc that have lots of GIS data. They will see no benefit from this change and bear the majority of the costs. I'm just hoping that these organisations have a sufficient budget to enable GIS staff to properly address the issue because if they don't there will be some interesting times ahead.
Apparently organisations are supposed to be able to prepare and convert at their own leisure. This ignores the fact of the increased reliance on CORS. The real truth is that the majority will have to convert at the same time as the CORS networks. So much for choice!
The Australia proposal is a two stage one. Starting 1 Jan 2017, the coordinate system will shift approx 1.8m and then starting 1 Jan 2020, the fixed system (that starts 1/1/2017) will operate together with a fully dynamic datum. The issues will come with inadequate meta data so a coordinate may be the old MGA1994, the new MGA2020 or the new MGA dynamic. All three coords for the same point in the ground will be within 2m or each other!
No cost benefit report has been done. I attended an ISCM meeting last year and asked about this and got shrugs as a response. They are fiddling with national infrastructure with no idea of the eventual cost. I am just glad that the same people are not in charge of the roads here as their decision process would lead to the something like this: "the majority of the world has left hand drive cars so we should too to save car makers the inconvenience of making right hand drive cars" and order the change with very little thought to the costs and consequences of such a decision.
What do US surveyors think considering that you will be addressing the same issues come 2025?
(all this is NOT Esri's position)
I'm wishing that I was retired by then...seriously. Your post just sparked an idea--is going semidynamic or dynamic cheaper for the geodetic agencies? I know the NGS has been struggling with a hiring freeze (recently lifted, I believe), plus several retirements.
"Customers" complained bitterly to NGS when they released NSRS2007 and 2011 without any transformation software to convert between those and the earlier versions (HARN, etc.). You'd think they'd realize the customers aren't going to want to deal with a dynamic/semidynamic datum, even in several years.
Seb, post: 383711, member: 7509 wrote: The issues will come with inadequate meta data so a coordinate may be the old MGA1994, the new MGA2020 or the new MGA dynamic. All three coords for the same point in the ground will be within 2m or each other!
It seems to me that the lack of knowledge of the existence of the metadata, is the problem now. The changes are to ensure that when people are wrong, they are only wrong by a little bit, instead of 1.8m.
Is my understanding wrong that road locations had been done by actual travel of GPS data collectors along said roadways.?Therefore roads have already been established with the GPS coordinates that receivers would agree with, While an actual destination may come from a map, 2 meters is close enough. Too much concern about nothing, or are people actually depending on GPS to keep them centered in the traveled lane?
Paul in PA
As for locating road data, it would depend on if the GPS was autonomous or corrected (real-time or post processed). I believe to get accuracy sufficient for navigation would need corrected data. Of course if the road data is in NAD83 (2011), then the WGS84 (i.e. ITRF) real time autonomous position would have to be transformed. Otherwise you will be driving on the shoulder!
I believe that this issue is relatively unknown in the US, despite the efforts of NGS at education. You can only educate people who want to be educated. Often at state conferences there is a workshop on this issue, but it is the same people going.
I totally agree with Seb that all of this could be dealt with in software. One reason given for going dynamic is so that user devices will autonomously position on WGS84. But a simple transformation will bring that to NAD83 (2011), or whatever fixed datum is being used. The transformations would have to be updated for earthquakes, but that could be done "over-the-air" in the case of smartphones. Most users probably don't realize that services like OPUS, OPUS-RS, Trimble RTX, etc all do computations in ITRF (or IGS, pretty much the same thing), and at the end transform to NAD83 (2011) if the user requests it. And if I use AUSPOS (which returns positions in ITRF08) or similar services to position, I can easily transform from ITRF08 to whatever datum I need, as the transformation parameters are well known and published.
So, my personal opinion is that in the US we need two datums, one static and one dynamic, with software to deal with the constant slow movement of one system with respect to the other. And being slightly offset from geocentric, as NAD83 is, should not be a problem with software able to transform in real time.
mkennedy, post: 383744, member: 7183 wrote: "Customers" complained bitterly to NGS when they released NSRS2007 and 2011 without any transformation software to convert between those and the earlier versions (HARN, etc.). You'd think they'd realize the customers aren't going to want to deal with a dynamic/semidynamic datum, even in several years.
Here is what I perceived as the "read between the lines" NGS position on this from the presentations I've heard about the 2022 datum changes:
Look...we understand that all sorts of end users use the NSRS for varying purposes. We can't know what every industry or profession is doing now or will be doing in the future with these coordinates. Our mandate, as scientists working for a government scientific agency, is to create a spatial reference system that as closely corresponds to the actual physical characteristic of the earth as our skills allow. Period. We'll help to whatever extent possible given our budgetary and mission constraints, but in the end how you are able to efficiently use our NSRS data is ultimately your problem.
We (the surveying and GIS communities) have used the NGS products when they have been easy (relatively) to adapt to our purposes. I suspect ten years down the line we'll follow one of two paths: either someone will develop a simplified procedure to use a dynamic datum for the majority of our work (state plane coordinates version 2.0 with an approximate time scale factor to go from current positions to whatever fixed time frame is used based on generalized areas of similar movement) or Javad will release a product that does it all in a funny looking box atop the range pole and advertise it with cheesy graphics showing him riding a tectonic plate - and Kent won't approve.