Sailors thank Clinton

In a popular May Day move, US President Bill Clinton authorised the military administrators of the Global Positioning System (GPS) to remove the deliberate error that has prevented civilian users from receiving an entirely accurate reading. The move has been enthusiastically welcomed by sailing organisations, although a note of caution has also been added.

The GPS was already used widely as an aid to navigation, but sailor and event organisers can now consider more accurate plotting of race courses, particularly for offshore races, in addition to improved position fixes in general safety situations. The price of GPS units has fallen dramatically in recent years with handheld battery-powered units now selling for less than £200.

The upgrade to the system means an improvement by a factor of 10 for non-military users and is part of a programme which was first mooted by the administration in 1996. This latest step is to be reviewed annually until full implementation in 2006 when an additional 18 satellites will be in orbit.

Welcoming the news, Paddy Maguire, the president of the Irish Sailing Association, said: "It's a significant contribution in relation to those using navigation equipment, but shouldn't be taken out of proportion: over reliance should be avoided."

The ISA and other bodies have repeatedly stressed that GPS and other aids should not be used a primary means of navigation over accepted techniques.

The GPS system utilises a network of 24 satellites in fixed positions over the earth. Users on or close to the surface use receivers to work out their own positions by automatically calculating the signals from accessible satellites in each region.

However, as the system was originally intended for military purposes, an error known as Selective Availability (SA) only allowed estimates to within 30 metres.

The system also acquired a degree of notoriety in various conflicts through precision bombing techniques and stories of various missiles navigating themselves along urban streets to the target.

During such attacks, the GPS system was totally isolated from all non-US and allied military users so all civilian navigation relying on the system ceased. The White House statement this week stated that in future GPS would be isolated on a local basis only where the US was involved in military conflict.

Even outside these times, civilian users of the system will still not have full military accuracy although the improvement is already noticeable. A second signal is planned for the main GPS system by August of this year. A third signal is also envisaged some time later. These additional signals will assist in reducing the naturally occurring error that comes from various radio atmospherics affecting the signal coming from the satellites to the user's receiver unit.

The world rankings of the International Sailing Federation were published this week. This eagerly-waited update brought mixed news for Ireland's leading sailors, as encouraging results at several major regattas were expected to boost several sailors higher in their classes.

However, strong performances by lower-ranked sailors saw Maria Coleman slip one place to fifth in the Europe class. David Burrows also dropped two places to ninth in the Finn class in spite of a third place, his best yet, at the European Championships three weeks ago.

Star sailors Mark Mansfield and David O'Brien have improved 14 places to 21st overall and remain firmly on course for qualification at their world championships at Annapolis next week. Tom Fitzpatrick and David McHugh are ranked 39th in the 470 class with their world championships looming next week as well, while Jon Lasenby is 37th in the Laser ranks.