SECTOR is a utility to estimate coordinates and their one-sigma uncertainties at an arbitrary epoch of time for over 2500 global and regional continuous GNSS stations, with the largest concentration in Western North America.
A common set of RINEX data and metadata (e.g., antenna height, antenna model) from as early as 1992 are archived at Scripps Institution of Oceanography’s Orbit and Permanent Array Center (SOPAC) and analyzed daily by SOPAC and the Jet Propulsion Laboratory (JPL) as part of a NASA MEaSUREs project.
The coordinates (X,Y,Z) are expressed with respect to a geocentric Earth-fixed reference frame in the latest incarnation of the International Terrestrial Reference Frame (currently ITRF2014), as realized by the International GNSS Service (IGS).
The coordinates are also expressed in geodetic coordinates (latitude, longitude, and height) with respect to the WGS84 ellipsoid (semi-major axis, a = 6378137 m and inverse flattening, 1/f = 298.257 223 563), as well as with respect to NAD83(2011) as defined by the National Geodetic Survey (NGS). The user can choose either “WGS84” or “WGS84 and NAD83”.
All uncertainties (one-sigma) are given in meters in north and east directions for latitude and longitude, respectively, and for height above the WGS84 ellipsoid.
Using JPL’s analyze_tseri (ATS) software, the epoch-date coordinates are derived from a time series analysis of daily positions, independently estimated by JPL using their Gipsy-X software and by SOPAC using MIT’s GAMIT/GLOBK software.
Epoch-date coordinates are available for each of the individual time series (SOPAC and JPL). In addition, the independent SOPAC and JPL displacement time series are optimally combined into a single time series, called the “Combination” time series (see ATBD reference below).
Each of the three flavors of time series, SOPAC, JPL, and Combination, are also filtered using a Principal Component Analysis (PCA) to reduce noise due to a common signature seen at all stations. However, PCA is only performed for stations in Western North America.
Note: SECTOR coordinates are based on the parametric fit to the displacement time series for velocity, coseismic offsets, non-coseismic offsets (artifacts), annual and semi-annual signals, and postseismic motion (see ATBD reference below), not individual data points.
There are several time series versions (the default is Unfiltered Combination):
- Unfiltered Combination
- Filtered Combination
- Unfiltered SOPAC
- Filtered SOPAC
- Unfiltered JPL
- Filtered JPL
For U.S. West Coast surveyors including California Spatial Reference Center (CSRC) users, it is recommended to use the default unfiltered combination time series.
Important note: The coordinates are refined weekly as we collect and analyze more data so users should expect small changes over time for requests at the same epoch date. In addition, requests at epoch-date 2017.5 may differ slightly from the published values (see final report below).