LONDON, July 1 (Reuters) - With $2 million on the line at this month's SailGP Grand Final, every points penalty imposed by Craig Mitchell and his team of umpires during the season has had a potentially big impact.

But Mitchell, a professional umpire who will also be working as "rules adviser" for Germany's sailing team at the Olympic Games, appeared unfazed by any pressure as he oversaw the practice races for the New York Sail Grand Prix last month.

What is unique about SailGP's umpiring is that as the crews "fly" their foiling 50-foot catamarans thousands of miles away, every split-second call is made remotely from west London, taking the video assistant referee (VAR) concept to an extreme.

The software which allows the umpires to make rulings within seconds about incidents on the water is called "UmpApp". Based on technology first developed for the America's Cup, it gives the GPS position of each boat to within 2.5 centimetres.

"It's the kind of GPS that you put in a bomb .. They are proper military grade units we are using," Mitchell told Reuters in the control room of SailGP, the league set up by Oracle founder Larry Ellison.

Resembling air traffic controllers, the umpires track the race on screens showing colour-coded blobs and lines representing the 10 catamarans, which can also be seen whizzing past New York's Manhattan skyline and the Statue of Liberty at speeds nearing 100 kilometres per hour through live video.

The league, approaching its season finale in San Francisco on July 13-14, has decided to get tougher on penalising collisions on the water because of the cost and time involved for its technicians in repairing the one-design craft.

"We brought in some penalty points for contact and still people were hitting each other, so we doubled the points. So people are very nervous about getting close to each other now," said Mitchell.

DISPUTE RESOLUTION

After umpiring for nearly 25 years, Mitchell says that doing it remotely is proving better for making accurate calls, getting technological support and ultimately for the environment as the team and all their kit do not have to fly between events.

It is also safer and more comfortable.

"Following these boats at 50 knots in a power boat is really dangerous, and it really hurts. We've gradually moved from having people on the water to in a booth," said Mitchell, who communicates with his four fellow umpires via headsets.

"In terms of officiating you've got all the data so you can make accurate calls, and you can go back in time. You can look back at an incident instantly, whereas if you are on the water you only see it once and that's it," he said.

But the technology cannot replace the human connection.

"The downside is you don't get to see the teams ... that's the bit we miss," said Mitchell, adding that the umpires give the skippers and the crews a video debrief when they go through the details of any incidents.

One of the most startling crashes of this season's SailGP was when Tom Slingsby's Australian crew ploughed head on into one of the marker buoys. Reigning champion Slingsby was heavily penalised for the damage to the "Flying Roo".

"That ended up at 12 (points) because it was serious damage, so that was huge," said Mitchell, who boils down the role of the umpire to "dispute resolution".

As they prepare for San Francisco, the impact of that crash is clear on the leaderboard, with Australia in second on 78 points, 15 behind Peter Burling's New Zealand crew.