PRECISE REAL-TIME DIFFERENTIAL NAVIGATION

USING NTRIP STREAMS FROM CONTINUOUSLY OPERATING,

WIDE-AREA GNSS NETWORKS.

Oscar L. Colombo

GEST/NASA Goddard Space Flight Center Maryland, USA

COMMENTS• NTRIP data freely available from GNSS networks provide

an invaluable test-bed for innovation.• SBAS networks now begin operations, or are under

development, in several countries, including developing ones, while more plan to build their own in the future.

• Wide-area precise real-time kinematic positioning (with “floated ambiguities”) typically needs a long time (30min – 1.5 hs) assimilating data before the solution converges to its full precision.

• New signals (L2C, L5, P5) can help shorten the convergence time, but their transmitter code biases have to be corrected using estimated values. Also the non-integer part of un-differenced L1, L2 ambiguities could be calibrated with data from the world-wide IGS network, to assist wide-area point-positioning.

• The IGS (or some IGS’ ACs) could help by providing some, or all, of the corrections mentioned above, much as CODE does now with the P1-C1 biases.

Map: BKG, Frankfurt

NTRIP Sites, Many Available through BKG(Mostly 1 Hz GPS data, Raw or RTCM 2.x, 3.0)

Some countries are developing or considering SBAS, DGPS, Precise DGPS. More could soon join them.

Source: BKG, Frankfurt

USA Off-Line Test, April 2004

The “IT” Real-time navigation software has been developed with

support from the US Navy (NSWC-Dahlgren Division)

Spanish Sites’ Test, 25 February 2008

Iberian Test Sites, April 28, 2008

A WORD OF CAUTION:First Sunspot of Cycle 24 Already Sighted

Prof. Claudio Brunini, UNLP

Near Solar Max., Ionospheric Scintillation can be a serious problem at low latitudes

(Tropical Anomaly)