Image copyright Strava Image caption The outline of the Welsh dragon, created by Alan Stone and Martyn Driscoll using Strava

Two Cardiff runners have used a GPS tracking app to draw the outline of a giant Welsh dragon.

Martyn Driscoll and Alan Stone ran the length of a marathon to create the art work using the running app Strava.

The 28-mile (45km) route in Upper Brynamman, Carmarthenshire, took them more than eight hours.

The route was plotted by tracing the dragon's outline on a map and then using the app to track their run.

When uploaded to Strava, the route shows up as a picture.

The pair did their dragon run on 1 April and said their friends did not believe it was real at first - but they eventually convinced them it was genuine and not an April Fool.

Image copyright Martyn Driscoll

Mr Stone, 57, from Whitchurch, said: "We needed to chose an area which was quite big, on open land with no fences, major rivers or roads or cliffs to fall off.

"You just have to follow the way the app is showing you. There were a couple of quarries we had to go around, so if you look at the tail it's a bit wobbly.

"I don't think anyone has done anything so detailed over such a large area before. It was great fun and kept us entertained on a wet day."

Mr Driscoll, 38, from Radyr, said the pair were inspired by other people doing similar things on Strava from across the world.

"The images people have created are quite basic and we wanted to test ourselves. What could be better than doing the Welsh dragon?" he said.

"It was quite easy to navigate using an iPhone with a spare battery pack.

"We are both competent runners but it took us a lot longer than we thought. At the bottom there was a huge bog which slowed us down, but we persevered."

A number of "Strava artists" have previously made headlines for using the cycling app to plot drawings.