Table 1.
Models used to produce the ITSG 2016 and ITSG 2018 series
| ITSG 2016 | ITSG 2018 | |
|---|---|---|
| Earth rotation | IERS 2010 | IERS 2010 |
| Moon, sun, and planets ephemerides | JPL DE421 | JPL DE421 |
| Earth tide | IERS 2010 | IERS 2010 |
| Ocean tide | EOT11a | FES2014b, co-estimated |
| Pole tide | IERS 2010 (constant mean pole) | IERS 2010 (linear mean pole) |
| Ocean pole tide | Desai 2004 (IERS 2010) | Desai 2004 (IERS 2010, linear mean pole) |
| Atmospheric tides (S1, S2) | van Dam, Ray (2010) | AOD1B RL06 |
| Atmosphere and ocean dealiasing | AOD1B RL05 | AOD1B RL06 |
| Relativistic corrections | IERS 2010 | IERS 2010 |
| Permanent tidal deformation | Included (zero tide) | Included (zero tide) |
1 Based on information from TU Graz website (https://www.tugraz.at/institute/ifg/downloads/gravity-field-models/, accessed on 25.01.2022)
Figure 1.
Methodology flowchart, which shows all the calculation steps
Figure 2.
Comparison of the (a) χ1 and (b) χ2 components of nonseasonal series of GAO, HAM + SLAM, and HAM obtained from ITSG 2016 and ITSG 2018
Table 2.
Comparison of STD, min, and max values from χ1 and χ2 nonseasonal series of GAO, HAM + SLAM, and HAM obtained from ITSG 2016 and ITSG 2018
| STD [mas] | Min [mas] | Max [mas] | ||||
|---|---|---|---|---|---|---|
| Series | χ1 | χ2 | χ1 | χ2 | χ1 | χ2 |
| ITSG 2016 | 5.48 | 7.28 | −15.91 | −23.15 | 19.46 | 24.25 |
| ITSG 2018 | 3.90 | 5.05 | −12.04 | −14.11 | 14.03 | 17.84 |
| GAO | 13.71 | 21.76 | −67.01 | −76.18 | 42.90 | 76.10 |
| HAM + SLAM | 1.99 | 2.24 | −6.65 | −7.38 | 6.68 | 7.18 |
Figure 3.
Comparison of (a) χ1 and (b) χ2 amplitude spectra series of GAO, HAM + SLAM, and HAM obtained from ITSG 2016 and ITSG 2018 from 20 to 120 days
Figure 4.
Comparison of (a) χ1 and (b) χ2 amplitude spectra series of GAO, HAM + SLAM, and HAM obtained from ITSG 2016 and ITSG 2018 from 2 to 20 days
Figure 5.
RMSEs of ITSG 2016-based series, ITSG 2018-based series, and HAM + SLAM calculated using GAO as the reference series. The exact RMSE values are given above the bars for each series.
Figure 6.
Varexp of ITSG 2016-based series, ITSG 2018-based series, and HAM + SLAM calculated using GAO as the reference series. The exact explained variance values are given above the bars for each series.
Figure 7.
Correlations between ITSG 2016-based series, ITSG 2018-based series, GAO, and HAM + SLAM in (a) χ1 and (b) χ2
Table 3.
Correlation coefficients between GAO and ITSG-based HAM series computed from ITSG 2016, ITSG 2018, ITSG 2016 with changed AOD1B data (AOD1B RL06 instead of RL05), and ITSG 2018 with changed AOD1B data (AOD1B RL05 instead of RL06)
| ITSG 2016 | ITSG 2016 RL06 | ITSG 2018 | ITSG 2018 RL05 | |
|---|---|---|---|---|
| χ1 | 0.35 | 0.31 | 0.35 | 0.32 |
| χ2 | 0.51 | 0.30 | 0.41 | 0.56 |
Figure A1.
Comparison of (a) χ1 and (b) χ2 amplitude spectra series of HAM + SLAM and HAM obtained from ITSG 2016 and ITSG 2018 from 2 to 120 days
Figure A2.
Comparison of (a) χ1 and (b) χ2 amplitude spectra series of HAM + SLAM and HAM obtained from ITSG 2016 and ITSG 2018 from 2 to 20 days