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iGage iG9 User Manual
The user location can be up to 50 KM from the polygon surrounding the selected sites which allows
OPUS-RS to succeed in coastal areas where there are no CORS sites offshore. However, every CORS
site that is used must be within 250 KM of the user site.
If you are in Michigan:
There are plenty of CORS stations within 250 KM of everywhere. OPUS-RS is likely to always succeed,
even if a few of the stations are offline, are missing data or are very noisy and must be discarded. It
is likely that OPUS-RS will work all the time in Michigan.
If you are in the middle of Utah there are very few CORS sites available on the best of days:
On a bad day, if a few stations are offline or have not yet archived data then your OPUS-RS solution
will fail because there are not enough stations close to your occupation.
In many areas a single offline CORS station without data will make OPUS-RS use impossible.
#4 Daily vs. Hourly CORS Availability
If you click a CORS station pin on the NGS CORS map, you will get a station summary which includes
an ‘Availability’ note. There are two availably types:
Daily
Hourly
Daily means that a full day’s CORS station data is collected and then sometime after midnight UTC
the data is archived and becomes available for use as CORS data. Collection is ONCE PER DAY.
