NEW YORK (Reuters) — Exhausted and triumphant from what was surely a ten-mile run through the neighbourhood, you get into your car to retrace your route and clock the distance.You check the car's odometer. Eight miles, it reads. Only eight miles? How can that be?

It's the sort of disappointment that is well-known to most runners, walkers and cyclists, who for years could make only rough estimates about how far or fast they went.

That's changing, however, thanks to a host of websites like MapMyRun (http://www.mapmyrun.com), WalkJogRun (http://www.walkjogrun.net), MotionBased (http://www.motionbased.com) and USA Track and Field's America's Running Routes (www.usatf.org/routes).

The idea behind the sites is to allow everyone, from casual athletes to professionals, to put their courses on a map.

Chris Pilla, a veteran of 40 marathons, is on MapMyRun two or three times a week.

"Once I saw it, I loved it," he said. "It's easy to navigate, it's easy to see, it works well with my computer."

Pilla is a coach for Team in Training, the Leukaemia & Lymphoma Society programme that raises money for research and services while providing training programmes for long-distance running. He uses MapMyRun to create courses around Princeton, New Jersey, where his team trains.

"I've got distances through the town of Princeton anywhere from a 4-mile run up to a 21-mile run that we use," he said. "I can tweak them based on an event that a person is training for, if it's got more hills, if it's flatter, whatever."

He then prints the course maps and passes them out to his team before group runs.

Creating a map on MapMyRun starts with entering an address, whether in your neighbourhood or some place you may be visiting on business or vacation. A simple map then appears, provided by Google, and users are asked to use their mouse to click around and create a course.

You can view the course using satellite pictures, calculate the mileage and judge how hilly the route is. Later you can go to a special section where you can calculate your pace and the number of calories burned, based on your age, sex, weight, and time it took you to complete the run.

Courses can be saved and shared with other runners, said MapMyRun co-founder Jeff Kalikstein, who makes changes to the site according to requests posted on his blog.

Kalikstein calls MapMyRun a part-time hobby that he became involved with after he got more serious about running and started writing software to work with his global positioning system wristwatch.

"I was living the cubicle lifestyle, not necessarily being very healthy, and put on some weight after college," he said. "I thought: 'I need to do something about this.' So I started running. Now we want to encourage other people to do the same thing."

Like Kalikstein, many runners are now tracking their activities through GPS systems, whether on cell phones, watches, or devices clipped onto shoes.

Indeed, Garmin Ltd., a maker of GPS devices, owns the MotionBased website, which allows users not only to map runs, but also to collect and analyze detailed data.

Athletes can download maps from MotionBased to their wrist or shoe devices to be sure not to lose their way. They can also upload data from their devices to the Web site to create graphs and charts showing everything from speed, distance and heart rate to elevation, time or even the weather and wind speed.

"It's not only that people can search and see where a route would take them, but they can put it into the device for navigation," said MotionBased marketing manager Mike Maxson.

Co-founder Aaron Roller created the site to help collect and sort information from a Garmin GPS device he had received as a gift. About a year ago, Garmin bought the site.

MotionBased offers subscriptions for about $95 a month, but also has a free service with a broad range of functions. It has about 50,000 users and a vast library of maps for activities that include hiking, skiing, running, and climbing in areas ranging from California to China.

"We get great feedback on this," said Maxson, who added that many of the staff are weekend warriors who use the site. "We have a lot of fun."