New Realization of WGS84

Thanks John, I knew this was close to being released, my oh my, new ITRF, new WGS84, new NAD83, new geoid model, lots of stuff to keep straight this year!

Do you know if there will be a EGM12 geoid soon too?

SHG

THAT does it. I hereby am renewing my membership in the flat earth society. Yikes! I've been slaming solutions lately before OPUS changes and we have to do all the conversion by hand again. Sigh.

New Realization of WGS84>Confusion abounds!

You know what?

This is why trying to use SPC for everything is just plain dumb.

Can you even imagine how you would ever explain to a judge or jury that SPC change and the point doesn't (bound that is). But to convert to SPC we have to 1) know the elipsoid of the day; 2) know the Geoid of the day, and then 3)jump between various datums using corpscon etc...

I can understand having a nice easy system for in house use, and for submitting to GIS for the towns, because the accuracy will be "close enough" But, how can you ever argue that SPC will someday control property corners? Not so long as it keeps changing, and with continental drift it's going to change. Amd so long as someone keeps finding a better elipsoid, or as we acquire more geoid data....

And how do you build a large building with grid dimensions or coords? Gotta convert!!

Doesn't that all sound like a bunch of make work??

Go ahead, slap me with the wet noodle, it's been a long day and I'm grumpy anyway!! 🙂
(oh yeah and first day without cigarettes makes me a little "pissy")

Don

New Realization of WGS84>Confusion abounds!

Don-

Right on !!

DGG

PS

Congrats on being smokeless.

How's your # 1 GPS daughter doing ?

New Realization of WGS84>Confusion abounds!

Amen brother! I couldn't agree more!!

Of course when the meter (or metre) is updated in value due to a more recent and more accurate definition of the distance from the north pole to the equator through Paris we will be able to define an even more useful WGS84.

And of course the "old" meter may still linger for a while as the "US Survey Meter".

I use WGS84 everywhere in my area on horizontal control as I match it consistently 0.02±.

Looks like a read with morning coffee.

Since the National Geospatial-Intelligence Agency (NGA), who define and manage WGS 84 don't provide any terrestrial realization for the system (e.g. CORS or passive marks) that we in the civilian community can access how do you (or anyone else for that matter) get WGS 84 positions +/- 0.02 ft?? The only way any of us in the civilian community can access real WGS 84 values is by autonomous point positioning which gives you +/- 3-4 m.

Howdy,

I thought the new WGS84 realization was released in February? See: http://earth-info.nga.mil/GandG/sathtml/gpsdoc2012_02a.html - Effective date February 08, 2012

For some interesting technical information about attempts to keep WGS84 and ITRF consistent see:

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA326324
http://earth-info.nima.mil/GandG/sathtml/IONReport8-20-02.pdf

As the esteemed Mr. Doyle indicates, the term "WGS84 coordinates" seems to be frequently misused. The 8 February document does refer to WGS84 precise orbits. Who uses them other than DOD elements? Perhaps when working on US military installations there is a requirement to provide WGS84 coordinates. In that case I would hope the DOD would provide monument information and their coordinates in WGS84.

Cheers,

DMM

"Who uses them other than DOD elements? "

Apparently more than would be accounted for by esteemed geodesists of the DOD.

There is a WGS84 requirement at many DoD installations, HOWEVER at others I have been asked to provide NAD83 positions, usually in SPC.

Not all installations have DoD provided WGS84 monumentation.

While not exactly the same, for all intents and purposes WGS84(G1674) is essentially coincident with ITRF08 as each time the ITRF is updated there is an adjustment of WGS84 to align with the newest version of ITRF.

Therefore, except for the most exacting demand for absolute WGS84 coordinates, civilians can have WGS84 positions as there are tools readily available most notably the NGS program HTDP to obtain ITRF / WGS84 from NAD83, in addition OPUS actually returns ITRF08 positions directly which at the 1-2 cm level are the same as WGS84(G1674) positions. (The 1-2 cm level applies to the previous WGS84(G1150) alignment to ITRF00, I am making the assumption that the new alignment is as good or better, BUT have not read any papers as of yet stating that fact)

In some cases this procedure might even produce a better absolute WGS84 position than NGA produces themselves as I have seen installations were the official NGA WGS84 control was established using precise point positioning, of course that isn't to say as a contractor on the installation you wouldn't use the provided monuments in the ground and the record positions, as with any survey a more accurate absolute coordinate may not be the required goal, instead matching the less accurate exisitng control might be the goal.

In ALL cases post the original WGS84 and original NAD83 there is a difference between NAD83 and WGS84, unfortunately many, dare I say most software programs still assume they are the same and that can and will screw something up if you accept that as true.

SHG

Give that man a kewpie doll - Shelby nailed it. Regrettably we deal with users almost on a daily basis that don't know this. They assume that NAD 83 and WGS 84 are the same (different by about 1 m each in horizontal and ellipsoid height), and in the vast majority of cases don't know that like NAD 83, WGS 84 has gone through several iterations.

foggy

That's why I always request NAD83 (CORS96) Epoch 2002.0 so they are all on the same page.

Dave

I think Andy was picking at the situation. 🙂 I'm sure he knows what he said was in error, but did it to make it look like he did. 🙂

"post processing" without any height differential B-)

foggy>>Kris

> That's why I always request NAD83 (CORS96) Epoch 2002.0 so they are all on the same page.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

And I do most of my work in NAD 83 epoch 2010, latest and greatest, no?

It really doesn't make a difference to me since it's all just a matter of button pushing, but you do have to know 1) what to ask for, and 2) what you're getting!

I am working on a site now that has SPC coord's for the building layout. Of course the coordinates don't match once you start calculating the column lines intersections and so on. So, one coordinate will be held and a line of the building will be held. I don't do layout myself, but I do quality control for the contractor on this site. Last building got skewed about 5 minutes over the 500' length. Not a big deal since the all the anchor bolt locations were in good relative location to each other. Just that the hanger wasn't parallel to the taxi way by 3/4's of a foot.....

I don't think that most folks are educated enough to understand the iterations of working with SPC.

Don

New Realization of WGS84>Confusion abounds!

good luck with the smoke free lifestyle
my buddy Tommy smoked for 35 years and quit cold turkey the day after his 50th birthday. you'd like him, he's a deadhead.

as far as the systems, it is obvious what will have to happen before the coordinates will fully control boundaries: we will need our software to quickly convert between the iterations of the datums and also take into account continental drift. isn't the ALTA / ACSM Survey Summit based on 4d points (assuming they are using the simplified theory of the 4th dimension being time). i think it will be fairly easy to show the judge how the change in the coordinate system changes some numbers but the point is in the same relative location. just take the obtuse example of geographic coordinates v. state plane. our current software lacks the necessary simplified metadata attached to each location of each point; someday someone will fix that.

additionally, too many of the monuments I find are not in their original and undisturbed locations. contractors, landscapers, homeowners and even people driving appear to aim for the bounds. subsequent monuments are often found in locations that do not match the original monuments. I can rely on a coordinate - even if it changes by a transformation - because I know that some contractor did not rip it up and put it back 'in the same spot'.

see the future, it's not going to be with ground based monuments. NGS is doing away with theirs... how far behind them are we?

New Realization of WGS84>Confusion abounds!

Whenever possible, connect the survey with proper adjustments to the Massachusetts Plane Coordinate System. [250 CMR 6.01(1)(C)(5)]

Dave, what's really concerning is that most folks out here never contact you at all! I would guess that you hear from less than 10% of us in the public sector. There are multitudes of folks running around with electronic boxes that have no clue what they are doing...