Gear

I was on Tryfan last Bank Holiday Monday and at the top my Viewranger was still showing me to be a few hundred feet shy? Does it measure the height from sea level or from the base of the mountain? Either way I'm pretty sure it can't be right because even at base level where the A5 is, I know that Lyn Ogwen possibly has to be around 900 feet or more above sea level?

Cheers,

John

Vertical GPS accuracy is usually within 5m, but can easily be as much as 20m out. I wouldn't be surprised if the cheapest GPS chipsets sacrifice some vertical accuracy to keep costs down.

Most high-end GPS handsets include a barometric altimeter to help with this, but if you really wanted reliable figures you should probably just get it from your map

For good vertical accuracy on an eTrex  I've found I need a good lock and a fair bit of settling time.

If I turn on the unit from cold and let it decide where our front garden is the grid ref is good from the start but we can vary in height from below sea level to over 100m.  Leaving it to "think" a bit it homes in on the real figure (~ 50m).

Pete.

IJ - really surprised - mine is usually good to within about 10 - 20 metres.  But I use the map location more - much more useful, and I have a Suunto alimeter watch!