[PROJ] Plate motion models

Kristian Evers kreve at sdfe.dk
Mon Feb 14 00:39:41 PST 2022 

Even,

I clearly didn’t read the conclusion of the study very carefully when I originally added this. The conclusion is clear, we should include the translations from table 2. I don’t have a lot of time to really do a deep dive into the paper but from a quick read it is unclear to me if the translate rates in table 2 is only applicable for EURA and NOAM or if they are general translations to be used for all plates.

I would suggest to add them as new entries in the ITRF2008 init file, e.g <NOAM_T> or something like that.

/Kristian

From: Even Rouault <even.rouault at spatialys.com>
Sent: 11. februar 2022 23:33
To: Steve Riddell <sriddell at geocue.com>; proj at lists.osgeo.org
Cc: Kristian Evers <kreve at sdfe.dk>
Subject: Re: [PROJ] Plate motion models


Interesting... The "ITRF2008 plate motion model, Z. Altamimi, et al" paper (https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2011JB008930) says:

- "The estimated ORB could be considered as not significant at the 95 per cent confidence level (i.e. two-sigma confidence level)." (and indeed if you look the values at one sigma dy=0.22 ± 0.32 mm/year , the significance seems questionable) and "we found a small origin rate bias, at the level of 0.4 ± 0.6 mm/a (95 per cent confidence limits), which could be considered as insignificant",

- but also "However, the users are advised to use the complete ITRF2008-PMM parameters: the plate angular velocities (Table 3<https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2011JB008930#jgrb17142-tbl-0003>) and the translation rate components (Table 2<https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2011JB008930#jgrb17142-tbl-0002>)."

@Kristian : do you think we should alter the existing ITRF2008 values or add a ITRF2008_with_tr file that incorporates them (I guess from the ITRF2008 paper that this would be for all plates, even if HTDP only mentions that for the 3 plates of interest for the US), the later would be advised for people wanting to reproduce HTDP values ?

(note: I don't pretend to understand the paper :-))

(note2: Table 2 of https://geodesy.noaa.gov/TOOLS/Htdp/HTDP-user-guide.pdf has also a lot of values for secondary and tertiary plates for ITRF2014 coming from other sources than Z. Altamimi et al, 2017, ITRF2014 plate motion model


Le 11/02/2022 à 22:27, Steve Riddell a écrit :
It did not occur to me initially, but all I had to do was add +dx/dy/dz terms in the Helmert string for NOAM in the init file. It works perfectly.

From: Steve Riddell
Sent: Wednesday, February 9, 2022 3:43 PM
To: Even Rouault <even.rouault at spatialys.com><mailto:even.rouault at spatialys.com>; proj at lists.osgeo.org<mailto:proj at lists.osgeo.org>
Cc: Kristian Evers <kreve at sdfe.dk><mailto:kreve at sdfe.dk>
Subject: RE: [PROJ] Plate motion models

Thank you again for the assistance. That was a huge help. It works as expected, based on the delivered ITRF2008/ITRF2014 init files.

Perhaps it should be noted that the delivered models support only 3-rotation parameters. The paper, “ITRF2008 plate motion model, Z. Altamimi, et al.”, and the HTDP documentation indicates that plates NOAM, PCFC, and CARB, include translation rates as well: (0.41,0.22,0.41)mm/yr.  The practical difference then is sub-centimeter, but noticeable when comparing with HTDP (over areas not covered by HTDP’s velocity grids).

Thanks again,
steve

From: Even Rouault <even.rouault at spatialys.com<mailto:even.rouault at spatialys.com>>
Sent: Monday, February 7, 2022 9:18 AM
To: Steve Riddell <sriddell at geocue.com<mailto:sriddell at geocue.com>>; proj at lists.osgeo.org<mailto:proj at lists.osgeo.org>
Subject: Re: [PROJ] Plate motion models


Hi Steve,

Assuming lon=-100 lat=40 z=0,  I believe (not sure! and in particular if that's geodetically meaningful to chain so many transformations) you should use a pipeline like the following one, which will do:

- conversion to cartesian coordinate space

- apply the ITRF2000 to ITRF2014 transformation preserving observation epoch of 2022.1

- apply the ITRF2014:NOAM model using a target epoch of 2010 (hence the +inv, as naturally the transformation would use +t_epoch as the "source") for a point at observation epoch of 2022.1

- force the observation epoch to 2010

- apply the ITRF2014 to ITRF2000 transformation (at epoch 2010)

- conversion to lat, lon coordinate space

echo -100 40 0 2022.1 | cct -d 8 +proj=pipeline \
    +step +proj=cart +ellps+GRS80 \
    +step +inv +init=ITRF2014:ITRF2000 \
    +step +inv +init=ITRF2014:NOAM +t_epoch=2010 \
    +step +proj=set +v_4=2010 \
    +step +init=ITRF2014:ITRF2000 \
    +step +inv +proj=cart +ellps+GRS80

I get:

-99.99999790     40.00000064    0.00755196     2010.0000

If using ITRF2008 instead of ITRF2014, I get:

  -99.99999854     40.00000065    0.00909276     2010.0000



I've also tried using a plate-fixed CRS as an intermediate using what is available in EPSG

First with NAD83(CORS96) since there's a direct transformation for it in EPSG (not quite "direct" since when looking at the comments, it already results from concatenation of ITRF96>97 and IERS ITRF97>2000 transformations)

(order is lat, lon here)
$ echo 40 -100 0 2022.1 | cs2cs -d 8 "ITRF2000" "NAD83(CORS96)" | cct -d 8 +proj=set +v_4=2010 | cs2cs -d 8 "NAD83(CORS96)"  "ITRF2000"
40.00000067    -99.99999766 -0.00447640     2010.0000

Or if using NAD83(2011) (there's a transformation between NAD83(2011) and ITRF2008 in EPSG (concatenation of ITRF96>97 and IERS ITRF97>2008 transformations), and PROJ will use the ITRF2008 to ITRF2000 transformation in addition
$ echo 40 -100 0 2022.1 | cs2cs -d 8 "ITRF2000" "NAD83(2011)" | cct -d 8 +proj=set +v_4=2010 | cs2cs -d 8 "NAD83(2011)"  "ITRF2000"
40.00000066    -99.99999765 -0.00447668     2010.0000

So results are somewhat consistent, at least in the lat, lon space (not for z values)

Best regards,

Even


Le 07/02/2022 à 14:49, Steve Riddell a écrit :
The data for the ITFR2008 & ITRF2014 plate motion models are delivered with PROJ as init files. From the documentation, 8.7, I think I see how an +init proj string can be used for changing epochs between ITFR frames (e.g. ITRF2000 to ITRF2005), but can someone please give an example of using the plate models? For example, if I have a point in ITRF2000 epoch 2022.1 and I want to use the NOAM plate model to move it to 2010.0, what would be the +init string? I’m assuming cct would be an appropriate application for processing this string?
Thanks for any assistance!
Steve


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