5. Conclusions

Measurement of OLT vertical deformation with millimeter level uncertainties from GPS data alone appears possible for the M2, S2, N2, O1, P1, and Q1 harmonics. GPS derived K1, and especially the K2 parameters show significant errors which additional research may reduce.

These results showed good agreement with the existing OLT models, particularly the more recent enhanced models, in all regions examined. It should be possible for OLT measurements from permanent GPS tracking sites to contribute to developing and refining OLT models in the future. In the interim, measurements of OLT parameters could be generated from the GPS data to confirm existing models or replace values in regions where significant model errors are suspected.

Estimation of OLT parameters from GPS would require additional terms in the data processing observation equation which imposes an additional, non-trivial computational burden, but not an overwhelming one given the rapid increase in computer capabilities. Distributed processing, already in use in some organizations, can further reduce this burden reducing it to an easily manageable level.