I seem to be becoming GPS enabled in all walks of life these days. First there was my eTrex which I used for checking my speed whilst windsurfing and then used for walking and geocaching in the hills. Then I got a TomTom One XL for my birthday which I use in the car and I've just bought myself a Garmin Forerunner 305.

This really is a cool piece of kit. A little bigger than a normal watch, but it has GPS built in. the receiver is better than the one in my eTrex and the accuracy better too. It also has a wireless heart rate monitor as well. It comes with a USB cradle so after a day cycling in the hills oyu can just clip it into its cradle and use the software to find out all sorts of interesting things.. The route you took is automatically super-imposed on a Google Earth map/satelite image... Here's one from the Pendam Trail earlier this week, using the software you can then show various stats along this route such as your speed, heart rate, pace, elevation, gradient etc. It also gives you loads of graphs and such like showing all of these stats and more.

It is supposed to be waterproof and a few peopl do use them for windsurfing, but i haven't decided to be brave enough to use it like this yet.. I might put it in an Aquapac and take it with me though... Would be good to see where I go, what sort of speeds I get on each tack and of course my heart rate when confronted by big walls of whitewater!!

All in all a pretty cool gadget.

Al.

Alan, very nifty.

Could Dunks use it to check his altitude during his jumps?

jon

LOL... Altitude isn't supposed to be that accurate, but I compared the altitude readings from a ride the other day with those from an OS map and they were pretty much spot on. There was a little discrepancy as far as absolute readings were concerned, but only a few feet, and relative readings surprised me with their accuracy... I'm not sure how it calculates the altitude though?

Al.

GPS calculates your 3d position (altitude) the same as your 2d position. A GPS receiver needs at least three satellites to calculate a 2D position (latitude and longitude) and to track movement. With four or more satellites it can calculate altitude as well, producing a 3D reading. Its all done by time. The satelites all have atomic clocks, they transmit time continuously to a ground station which has a similarly accurate clock. The time taken to travel to the ground station gives the satelite's precise location. Your GPS software then picks that data up from the ground station and computes the exact positions of the satelites to work out your location.

GOD - I'm sounding really anal now aren't I!!

Ahhh...But many of them use barometric altimeters rather using GPS as GPS isn't very accurate for altitude readings.

Al.

Phew... Went for a run today and got my heart rate up to 180bpm.

Of course once I got back from the run I had to have 3 bacon and egg sarnies to make up for it!

Al.