The questions about ITRF97 are good ones, but the reality is that we can't submit any papers using ITRF97 - we must move on to ITRF2000, so this explanation only covers ITRF2000.

Positions in ITRF2000

I am still making the plots for this section.

ACAP MDO1 CAYA PINO OAXA ZIHP YAIG IGUA CHIL

The ITRF2000 velocity for MDO1 is -12.1, -7.2, -0.6 in (mm/yr ENV). The estimate from the GIPSY values is -13.0, -7.2, -0.8 (mm/yr ENV), which is good agreement (both values have sigmas, which are not shown).

The NOAM NNR-NUVEL1A velocity for MDO1 is -12.0, -7.1, 0.0 (mm/yr ENV)
The NOAM NNR-NUVEL1A velocity for ACAP is -7.4, -5.5, 0.0 (mm/yr ENV)

The good agreement between our GIPSY analysis and ITRF2000 and NNR-NUVEL1A suggests to me that if you want to convert the ppp results into NOAM fixed velocities, it is sufficient to substract the NOAM NNR-NUVEL1A velocities given above, i.e. -7.4 and -5.5 mm/yr in east and north components. We could subtract out an Euler based value, which I can extract from the official ITRF2000 publication.

Baselines

Caption: East/longitude is blue; green is north/latitude. Velocities are given in cm/yr.

The linear trends are based on data between 2000 and 2001.9. If ACAP were on the NOAM plate, its velocity relative to MDO1 is -4.8 -1.1 0.9 (ENV mm/yr)

You take the baseline trends and add the values above:

East: 19.1 - 4.8 = 14.3
North: 18.6 - 1.1 = 17.5

For the ITRF2000 positions you subtract out the values from the first section:

East: 5.5 - (-7.4) = 12.9
North: 12.7 - (-5.5) = 18.2

Given how I defined these velocities over such a short period of time, and did not do a rigorous removal of the outliers, I would say agreement to about a mm (1.4 mm/yr in east), is pretty good. Remember, a 5 year time series for MDO1 only agreed at the mm/yr level. I will check the ITRF2000 paper so that we have a better NOAM pole to use.