Using NGS Online Positioning User Service (OPUS)
Online Positioning User Service (OPUS) allows users to submit their RINEX (Receiver
Independent Exchange) format GPS data files online to the National Geodetic Survey
(NGS), where the data will be processed to determine a position using NGS computers
and software. Each RINEX file that is submitted will be processed with respect to 3
National CORS sites. The resulting position is automatically e-mailed back to the user.
You do not need software for baseline processing or least squares adjustment software
on your computer. You only need to download the file from your GPS receiver, convert
to RINEX format, and submit online to NGS.
At this time, NGS requires that you use a dual-frequency GPS receiver
have a plan to allow single-frequency receiver data in the future.
NGS requires a minimum of two hours of data per file, but recommends at least four
hours of data. To comply with BLM Cadastral GPS standards, I recommend doing two
four-hour sessions, breaking down your tripod and setting up again in between sessions
in order to achieve an independent occupation with an independent antenna height
You must download the files from the GPS receiver, convert the file to RINEX format,
and then submit the RINEX file to NGS via the OPUS on-line submittal form.
The following instructions assume a Trimble .dat file and Trimble Geomatics Office
(TGO) software; however, the executable for “Convert to RINEX” in TGO is
“dat2rinw.exe”, which can be run as a stand alone program without TGO.
Dat2rinw.exe, which is typically located in C:\Program Files\Common
According to the NGS, UNAVCO has developed software called TEQC (pronounced
TEK) that is freely available at http://www.unavco.org/facility/software/teqc/teqc.html."
TEQC will convert data files to RINEX format, but I have not used the TEQC software.
Converting the downloaded Trimble .dat file to a RINEX file in TGO.
1. Using Trimble Geographics Office (TGO), with all projects closed; pick
“Convert to RINEX” from the “Utilities” menu.