201205 May/June 2012 Archives - Page 2 of 2 - Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design

201205 May/June 2012

Demystifying GLONASS Inter-Frequency Carrier Phase Biases

EQUATIONS 1 -11

GLONASS currently uses a frequency division multiple access (FDMA) technique to distinguish the signals coming from different satellites in the Russian GNSS constellation. The GLONASS L1 and L2 bands are divided into 14 sub-bands, and each satellite transmits in one of these.

The sub-bands are identified by frequency numbers k, from -7 to 6. The GLONASS L1 and L2 carrier frequencies, in hertz, at a frequency number k are defined by:

Read More >

By Inside GNSS
May 24, 2012

How do GNSS-derived heights differ from other height systems?

FIGURE 2: Example of a national geoid (upper diagram) and a correction surface for the transformation from the new orthometric height system to the old height system (lower diagram). Country is Switzerland. Geoid undulations range from 45 to 55 meters in ETRS89 and from -5 to +5 meters in the national System CH1903+. Lower diagram: Correction surface to transform from the new orthometric height system (LHN95) to the old height system LN02 with corrections from -0.10 to 0.55 meters.

Q: How do GNSS-derived heights differ from other height systems?

A: Height estimation using GNSS always seems to be trickier than horizontal coordinate estimation.

Why?

On the one hand, the GNSS technique has error sources that are more critical in the vertical direction. Height estimates are weaker because of a combination of satellite geometry, the presence of strong correlations to other parameters, such as atmospheric delays, and the antenna phase center model applied during data analysis.

Read More >

By Inside GNSS

GPS Receiver Specifications

An increasingly urgent call to certify performance of Global Positioning System (GPS) receivers is being heard from several sectors of the national political and business landscape. This issue has arisen now as a direct result of the LightSquared initiative that has generated so much attention over the last 18 months.

Instead of diving into those issues directly, however, a little historical perspective is in order first — and it’s amazing in itself that a technology as new as GPS in the public eye would actually have a history to reflect upon, but it does.

Read More >

By Inside GNSS

Truth on the Range

Typical Rack-Mounted UHARS System

A next-generation “truth” reference system for the U.S. Air Force (USAF) — the Ultra High Accuracy Reference System (UHARS) — is currently under development by the 746th Test Squadron (746 TS) at Holloman Air Force Base, New Mexico.

Read More >

By Inside GNSS