A new US national space policy document unveiled recently by President Obama marks a major change of direction on the relationship between the country's GPS system and other GNSS systems around the world. And the change can only accelerate the development and interoperability of systems such as GLONASS, Compass and Galileo.

Whereas US policy as affirmed in a December 2004 national security directive was focused on maintaining the country's lead in GNSS on a unilateral basis, the new initiative reflects a more open attitude and calls for the USA to “engage with foreign GNSS providers to encourage compatibility and interoperability, promote transparency in civil service provision, and enable market access for US industry”. It also allows that “foreign positioning, navigation and timing services may be used to augment and strengthen the resiliency of GPS”.

The latest contender in the global navigation sweepstakes has moved a little closer with the launch of the fourth satellite in China's second-generation Beidou constellation during the first week of June 2010. Beidou (which means Big Dipper) will cover all of China and neighbouring lands by 2012, and will then be expanded to provide global coverage through a constellation of 35 Compass satellites by 2020.

Compass will differ from other GNSS systems in that five of the intended 35 satellites will be in geostationary orbit, while the other 30 will have medium earth orbits similar to the GPS, GLONASS and Galileo constellations.

Many world governments have a long-standing target for car manufacturers to reduce average CO2 emissions for their vehicles. The European Union target is 120g/km by 2012 and longer term to 80g/km by 2020. The view of the industry has been that this is very challenging and unlikely to be met via conventional approaches alone. Indeed, the 2012 target already represents a slip from an original 2005 target date. As most manufacturers will not be able to meet the 2012 target, further slippages (possibly to 2015) and concessions (exclusions for heavier vehicles) are already on the table.

So what has all this got to do with GPS? The answer is that GPS is one technology that might be able to help reduce vehicle emissions. How might this work? Let’s assume that your vehicle is a hybrid, running on batteries part of the time to help meet the 120g/km and certainly the 80g/km target. The more the batteries are used, the lower the emissions. Hybrid car systems have limits set on the depth of discharge that the battery systems can be taken to before the engine kicks in. Often these limits include quite large margins.