Post-processing your measurements by OPUS and others

Need to locate your base station?

In order to setup your base station you will need its precise location, expressed in ECEF (Earth Centered, Earth Fixed) coordinates, not in NAD-83, WGS84 or any other local datum.  This is typically done by the collection of several hours of data and some post-processing by a 3rd party service. Any error in your location will be reflected by an offset in the rover devices using it.

Here are the links to the most commonly used services, at least in the North American region.

In the US, and if you have both L1-L2 data, use CORS OPUS at:

http://www.ngs.noaa.gov/OPUS/

In North America, or if you only have L1 data, use the NR CAN PPP service at:

http://webapp.geod.nrcan.gc.ca/geod/account-compte/login.php

OPUS can be rather picky.  The NR Canada site is easier to use, accepts ZIP files, (and L1 only data files) and on the whole provides very robust results.  For any work in North America, we tend to prefer it. The NR Canada site requires you to create an account, takes only a few minutes.

Need to post-process your measurements in an “OPUS” like form in Australia?
Here is the link you were looking for:

http://www.ga.gov.au/scientific-topics/positioning-navigation/geodesy/auspos

For all of these sites, You will need ~4 hours of essentially clean data to submit.  What you get back you can use as the ECEF position of your base station device.  Enter this into the rovers software settings. SNIP will send it along with other correction messages to you NTRIP Clients.  If you are sending in an RTCM3 message style data stream, SNIP will also parse it from the stream and use it to populate the caster table entry for this stream automatically. You can check the final results by using SNIP‘s map display to confirm the precise location you expected.

Know of another site we should list here? – please post us a note below.

Update: Eric Gakstatter (GPS World) has written a very nice article on the topic of alternatives to OPUS at: http://gpsworld.com/a-comparison-of-free-gps-online-post-processing-services/

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