## 1 Introduction  
Time variable deformation of the Earth caused by ocean tides could reach up to 100 mm at some special coast regions [1,2]. With the growing demands for high precision geodetic observations, ocean tidal loading (OTL) correction has come a must in precise global positioning system (GPS) data processing with baseline lengths of up to several thousand kilometers. Up to now, many ocean tide models (OTMs) were provided by the ocean loading service [3], and geodetic users could easily implement OTL corrections by introducing global grid or station list files for different OTMs. The accuracy of the OTL values depend on the errors in the OTM, Green's function, coastline representation as well as the numerical scheme of the loading computation itself. Currently, the largest contributor to the uncertainty of the loading value is the errors of the OTM itself. Therefore, it is recommended to use the most recent OTMs, for example, the TPXO7.2 and the Finite Element Solution 2004 (FES2004) models [4]. The OTL at a particular location on the Earth caused by a given tidal harmonic is computed by integrating the tide height with Green's function over the whole ocean area [5], and the total impact of OTL equals to the effects of all tidal harmonics. The 11 discrete ocean tide constituents are considered sometimes in OTL modeling during routine precise GPS data processing, including displacement induced by four semidiurnal tide waves M2, S2, N2, K2, 4 diurnal waves K1, O1, P1, Q1, together with three long-period waves Mf, Mm, and Ssa [6, 7, 8]. Aside from these 11 main tidal components, however, other principle tidal constituents could also cause surface displacements, e.g., the larger and smaller solar elliptic semidiurnal waves T2 and L2, the smaller and small lunar elliptic diurnal waves M1 and J1, the long-period waves Sa Msf, _etc._[9,10]. The shallow water ocean loading tides (the third-diurnal and higher-frequency) can be large and significant too, for example, the shallow water constituent M4 exceeds 50 cm at several locations on the northwest European shelf, while the amplitude of the shallow water tides S3, S4 and S5 at the Japanese east coast reaches a few millimeters [11,12]. Since early February 2006, [PERSON] has posted a fortran routine hardisp.f by considering a total of 141 constituent tides from the 11 main tides, which then became a conventional implementation in November to calculate local site displacement due to OTL, and [PERSON] found that completely neglecting the other ocean tides and nodal modulations with only the 11 main tides may lead to errors of up to 5 mm weighted root mean square (WRMS) at high latitudes using the GOT00.2 ocean model [13,14]. Later on, the 141 constituent tides was included in most of the processing of most, if not all, analysis centers (ACs) for the first IGS reprocessing that contribute to ITRF2008 [15,16]. Thanks to the efforts of many OTL researchers, hardisp.f is being continuously updated online. Until now, it includes a total of 342 constituent tides whose amplitudes and phases are found by spline interpolation of the tidal admittances based on the 11 main tides, and has been implemented in most of the ACs' analysis strategy [17,18]. Currently, among the three most widely used precise GNSS data processing software, Bernese has already implemented the 342 constituents OTL correction, GIPSYconsidered an additional 32 smaller tidal components aside from the 11 principle tides, while the latest version of GAMIT still applied the 11 constituents OTL correction [19; 20; 21]. Here, among the total 342 constituents, we define all the other tidal constituents except for the 11 main tides as the minor ocean tides (MOT). Since many routine precise GPS data processing are being done by GAMIT, which is provided free for non-commercial application, the questions raised are what's the magnitude of station's displacement caused by MOT for global IGS stations? Do they have any impact on station's daily positions derived from the 24-hour GPS solution?