On 4/4/13 12:51 AM, gary wrote:
Isn't this what WAAS does?
http://igs.bkg.bund.de/ntrip/about
Yes..
There's lots of ways to get real time (or near real time) correction
data. WAAS is but one. TASS (experimental) is another. There's various
and sundry local High Accuracy Reference Networks (HARN) around, some
run commercially, some run by governments. Heck, you used to be able to
subscribe to corrections broadcast on a FM broadcast station subcarrier
like stock quotes and sports scores. These days, "the internet" is
probably the preferred medium.
Different corrections are in different formats for different end uses.
If you are flying a plane, you only need "meters" kind of accuracy and
you're probably using a L1 only receiver. If you're doing real time
kinematic surveying, you are looking for 1mm sorts of accuracy, so a
local reference station (or a synthesized reference station) would be
handy for taking out smaller ionospheric and solid earth tides kinds fo
things.
There are also lots of folks distributing corrections and reference
data. In the US there's commercial providers, so federally funded data
providers have to be careful about "government doesn't compete with
industry" rules. For instance, to get the JPL precision data, you need
to have an account and certify you're using it for educational and
research purposes, and not as part of a commercial enterprise. In other
countries, they just put it out there for anyone to use.
It's like mapping data, the availability of which (for free) varies a
lot from country to country.
{Political comment: I think that mapping and precision geodesy data is
a common good or infrastructure. It's an appropriate use of tax money to
provide universal access because there isn't a "business case" to cover
everything with equal performance. A fine example is USGS topographic
maps and NOAA Marine Charts. }
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