Technical description of the global solution opa2018a 1. Origin of input data: databases from IVS data center, version 4 or more. 2. Authentic processing steps after data retrieval: re-calc with Calc 11.0, transform to superfile and treat with BATCH Solve. 3. Origin of meteorological data: use database content. 4. Use numerical weather model: ECMWF for computing VMF1. 5. Setting of mapping functions: VMF1. 6. Origin of cable cal data: use database content. 7. Application of cable cal flags: use database settings. 8. Selection/settings of geophysical models: replace database settings. 8.1. Nutation/precession: IAU 2000A nutation and IAU 2006 precession. 8.2. Short-period tidal variations in x, y, UT1: IERS 2010. 8.3. Troposphere mapping functions: VMF1. 8.4. A priori mean gradients: from VLBI data or DAO weather model. 8.5. Solid Earth tide: IERS 2010. 8.6. Ocean loading displacements: FES 2004. 8.7. Atmospheric loading displacements: APLO. 8.8. Permanent tide correction: applied. 8.9. Thermal expansion: Nothnagel (2008). 8.10. A priori station positions and velocities: ITRF 2014 or database content for new stations. 8.11. A priori source coordinates: ICRF2 or database content for new sources. 9. Parameterization 9.1. Clock: quadratic + continuous piece-wise linear with 60-mn interval. 9.2. Atmosphere: continuous piece-wise linear 20-mn interval. 9.3. Gradients: estimated at 6-hr interval at all sites. 9.4. Earth orientation: polar motion and rate, UT1 and rate, nutation offsets. 9.5. Station positions: 9.5.1. Most of the station positions and velocities estimated globally at epoch 2000.01.01. 9.5.2. Jumps: YAKATAGA 871201 * Earthquake SOURDOGH 871201 * Earthquake WHTHORSE 871201 * Earthquake FORTORDS 891001 * Seismic event PRESIDIO 891001 * Seismic event MOJAVE12 920627 * Earthquake DSS15 920627 * Earthquake MEDICINA 960601 * Rail reparing EFLSBERG 961001 * Rail reparing DSS65 970415 * Rail reparing MIURA 000901 * Dike intrusion, June-Aug. 2000 TATEYAMA 000901 * Dike intrusion, June-Aug. 2000 GGAO7108 030101 * Station relocation MK-VLBA 061015 * Earthquake ZELENCHK 070701 * Rail repair ?????? USUDA64 110311 * Earthquake 9.5.3. Nonlinear position variations modeled with splines using Solve's option SPLINE_POS for: HRAS_085 PIETOWN GILCREEK 9.5.4. The data relevant to the stations used for polarization tests or backend tests were removed: NOTOX WIDE85_3 VLBA85_3 MOJAVLBA LEFT85_1 HARTDBBC YEBESDBC YEBDBBC ONSALAAN YEBEDBBC OHIGGADS WETTDBBC LEFTKOK LEFT85_3 NYALDBBC 9.6. Station velocities: mostly estimated as global parameters. 9.7. Source coordinates 9.7.1. All global except sources showing strong nonlinear displacements: 0014+813 0235+164 0637-752 0738+313 1308+326 1448+762 2145+067 3C120 1610-771 0208-512 0438-436 0451-282 0919-260 0607-157 2243-123 NGC1052 2128-123 3C279 0106+013 2134+00 1021-006 3C273B 0528+134 2121+053 0202+149 3C454.3 1611+343 OQ208 2201+315 2234+282 OK290 4C39.25 3C345 0711+356 3C84 1739+522 1044+719 0212+735 3C309.1 9.7.2. The data relevant to the following sources were removed: The radio stars: 0236+610 0459-753 1612+339 0334+004 0323+285 1458-083 The known gravitational lenses: 0218+35A 0218+35B 0218+357 1422+231 1830-21A 1830-21B 1830-211 9.8. Antenna axis offsets: estimated for the following sites which have observed in more than 5 sessions and treated as global parameters. 10. Outlier elimination: use database settings. 11. Constraints (only of interest for direct EOP estimates) 11.1. Sources: loose no-net rotation is uniformly applied to the 295 ICRF2 defining sources: 0002-478 0007+106 0008-264 0010+405 0013-005 0016+731 0019+058 0035+413 0048-097 0048-427 0059+581 0104-408 0107-610 0109+224 0110+495 0116-219 0119+115 0131-522 0133+476 0134+311 0138-097 0151+474 0159+723 0202+319 0215+015 0221+067 0230-790 0229+131 0234-301 0235-618 0234+285 0237-027 0300+470 0302-623 0302+625 0306+102 0308-611 0307+380 0309+411 0322+222 0332-403 0334-546 0342+147 0346-279 0358+210 0402-362 0403-132 0405-385 0414-189 0420-014 0422+004 0426+273 0430+289 0437-454 0440+345 0446+112 0454-810 0454-234 0458-020 0458+138 0506-612 0454+844 0506+101 0507+179 0516-621 0515+208 0522-611 0524-460 0524-485 0524+034 0529+483 0534-611 0534-340 0537-441 0536+145 0537-286 0544+273 0549-575 0552+398 0556+238 0600+177 0642+449 0646-306 0648-165 0656+082 0657+172 0707+476 0716+714 0722+145 0718+792 0727-115 0736+017 0738+491 0743-006 0743+259 0745+241 0748+126 0759+183 0800+618 0805+046 0804+499 0805+410 0808+019 0812+367 0814+425 0823+033 0827+243 0834-201 0851+202 0854-108 0912+029 0920-397 0920+390 0925-203 0949+354 0955+326 0955+476 0954+658 1004-500 1012+232 1013+054 1014+615 1015+359 1022-665 1022+194 1030+415 1030+074 1034-374 1034-293 1038+528 1039+811 1042+071 1045-188 1049+215 1053+815 1055+018 1101-536 1101+384 1111+149 1123+264 1124-186 1128+385 1130+009 1133-032 1143-696 1144+402 1144-379 1145-071 1147+245 1149-084 1156-663 1156+295 1213-172 1215+303 1219+044 1221+809 1226+373 1236+077 1240+381 1243-072 1244-255 1252+119 1251-713 1300+580 1308+328 1313-333 1324+224 1325-558 1334-127 1342+662 1342+663 1349-439 1351-018 1354-152 1357+769 1406-076 1417+385 1418+546 1420-679 1423+146 1424-418 1432+200 1443-162 1448-648 1451-400 1456+044 1459+480 1502+106 1502+036 1504+377 1508+572 1510-089 1511-100 1514+197 1520+437 1519-273 1546+027 1548+056 1555+001 1554-643 1557+032 1604-333 1606+106 1611-710 1614+051 1617+229 1619-680 1622-253 1624-617 1637+574 1638+398 1639+230 1642+690 1633-810 1657-261 1657-562 1659-621 1705+018 1706-174 1717+178 1726+455 1730-130 1725-795 1732+389 1738+499 1738+476 1741-038 1743+173 1745+624 1749+096 1751+288 1754+155 1758+388 1803+784 1800+440 1758-651 1806-458 1815-553 1823+689 1823+568 1824-582 1831-711 1842+681 1846+322 1849+670 1908-201 1920-211 1921-293 1925-610 1929+226 1933-400 1936-155 1935-692 1954+513 1954-388 1958-179 2000+472 2002-375 2008-159 2029+121 2052-474 2059+034 2106+143 2106-413 2113+293 2123-463 2126-158 2131-021 2136+141 2142-758 2150+173 2204-540 2209+236 2220-351 2223-052 2227-088 2229+695 2232-488 2236-572 2244-372 2245-328 2250+190 2254+074 2255-282 2300-683 2318+049 2326-477 2333-415 2344-514 2351-154 2353-686 2355-534 2355-106 2356+385 2357-318 11.2. Stations: loose no-net rotation/translation on positions and velocities is applied to a sub-network: ALGOPARK BR-VLBA DSS45 FD-VLBA FORTLEZA HARTRAO HATCREEK HAYSTACK HN-VLBA HOBART26 -ASHIM34 KASHIMA KAUAI KOKEE KP-VLBA LA-VLBA MATERA -K-VLBA NL-VLBA NOTO NRAO20 NRAO85_3 NYALES20 ONSALA60 OV-VLBA OVRO_130 PIETOWN RICHMOND SANTIA12 SC-VLBA SESHAN25 -SUKUB32 VNDNBERG WESTFORD WETTZELL SVETLOE YEBES40M HOBART12 KATH12M YARRA12M WARK12M 12. Generation of pre-reduced datum-free normal equations: will be done later in the SINEX (rapid) solution processed in independent mode. 13. Further details 13.1. Data type: group delays. 13.2. Data editing: 5 degree elevation cutoff. 13.3. Data weighting: weights are defined as follows: 1/sqrt(f**2+a**2) where "f" is the formal uncertainty of the ionosphere free linear combination of group delays at X- and S-band obtained by fringe fitting on the base of achieved signal to noise ratio. Station-dependent parameter "a" was computed for each session by an iterative procedure such that the ratio of the sum of squares of the weighted residuals to the estimate of their mathematical expectation is about unity. 13.4. Standard errors reported: all errors are derived from least-squares estimation propagated from the data weights and the constraints applied to the troposphere, clock and EOP parameters. 13.5. Software: Calc 11.0, Solve revision date 2017.xx.xx. 13.6. Other informations about the solution are reported at http://ivsopar.obspm.fr.