GPS precise point positioning (PPP) ambiguity resolution (AR) is a challenging task for ambiguity-resolved PPP. So far, two PPP AR methods, i.e. un-differenced decoupled clock model and single-differenced between satellites model, have been proposed. Various publications have demonstrated that the...More>>

The National Geodetic Survey (NGS) is conducting a 12-year project to re-define the vertical datum of the US. This project, referred to as GRAV-D (Gravity for the Redefinition of the American Vertical Datum), is accomplished by flying airborne gravity missions over the continental and coastal US. ...More>>

To reliably navigate with fewer than four satellites, GPS pseudoranges need to be augmented with measurements from other sensors, such as a reduced inertial sensor system or RISS. What is the best way to combine the RISS measurements with the GPS measurements? The classic approach is to integrate...More>>

JAVAD GNSS announced that it is partnering with broadband company LightSquared. In promotional material handed out at the ION-GNSS conference in Portland, Oregon, JAVAD GNSS says "LightSquared not only can coexist with GPS, it complements it."More>>

In this month’s column, we look at how a team of Dutch and Japanese researchers is using GPS to determine the attitude of a payload launched from a high-altitude balloon.More>>

The Garada project, funded by the Australian Space Research Program, aims to establish an Australian space engineering capability to provide a disaster-monitoring earth observation system. Satellite-borne earth observation is very important for Australia and for other countries that need to monitor...More>>

Multipath is real and omnipresent, a detriment when GPS is used for positioning, navigation, and timing. The authors look at a technique to reduce multipath by using a pair of antennas on a moving vehicle together with a sophisticated mathematical model. This reduces the level of multipath on...More>>

A look at how Doppler measurements can be used to smooth noisy code-based pseudoranges to improve the precision of autonomous positioning as well as to improve the availability of single-frequency real-time kinematic positioning, especially in urban environments.More>>

As announced in IGSMAIL-6354, the IGS will adopt a new reference frame called IGS08 that should be used together with igs08.atx, an updated set of receiver and satellite antenna phase center corrections. Those will replace the absolute phase center correction model igs05.atx adopted in November...More>>

As announced in the previous post, the IGS will switch from the (IGS05 + igs05.atx) framework to (IGS08 + igs08.atx) in the coming weeks. Many users have accumulated results expressed in the old framework, either based on the regular IGS operational products since November 2006, or in concert with...More>>