Recent Contribution to the ITRF and its Realization in Canada

Abstract

Natural Resources Canada (NRCan) is processing data daily from a subset of at least eight Canadian automated GPS tracking stations, the Active Control Points (ACP), and from at least twenty five of the International GPS Service (IGS) stations using a modified version of JPL GIPSY-OASIS II software. NRCan contributes to IGS solutions for satellite orbit, clock corrections, earth orientation parameters (EOPs), station coordinates and more recently tropospheric delays and ionospheric grids.

In the daily estimation process, station coordinates are constrained by a subset of station positions of the current epoch in of the International Terrestrial Reference Frame (ITRF). Removing a priori constraints is required for the rigorous station coordinate and velocity estimation.

In the most recent NRCan contribution to IERS, four years of daily station coordinates and EOPs were combined. A consistent set of station coordinates, velocities and EOPs were obtained by back substituting the final station coordinates in the daily solutions. The NRCan and ITRF station coordinate and velocity solutions were compared, as well as the NRCan station velocity estimates were compared to the NUVEL1A plate motion model. Analysis and comparison between the time series of residuals are also presented.

This approach, through the Canadian Active Control System, provides a convenient globally consistent realization of ITRF in Canada.