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Discussion Forum - Gear ! - GPS height gain data


Author: Tony Willey
Posted: Sun 21st May 2006, 18:28
Joined: 1989
Local Group: Lakeland
Information provided by GPS comes in 3 categories. "Where am I?" & "What height am I?" are potential life savers. "How far have I walked?" & "How much have I climbed?" are nice to know, and it was the apparent errors in the cumulative height gain data (and I'm talking hundreds of metres difference here) that caused me to start this thread off. Like most modern technology GPS can also provide lots of other information of marginal value - who really wants to know present and average rates of ascent/descent? After the initial novelty wore off I found that the GPS stays in my pocket most of the time, except in an emergency or if I am feeling too lazy to use the map & compass.
Author: Matthew Hand
Posted: Sat 20th May 2006, 9:55
Joined: 2001
Local Group: Mid Wales
We all want to know before an event what is involved. But for years we seem to have survived simply by measuring the distance on a map and counting the contours (have to wear my glasses for that bit)! Do we actually gain anything from the extra information supplied by modern technology - other than something to talk about and compare with other walkers afterwards. I normally have a pretty good idea if measurements are incorrect during an event, from a glance at the map and knowing my own speed and how I am going. I feel we are in danger of putting too much emphasis on exact measurements (simply because some can do it) and possibly running down those events that get things slightly wrong in this department - when it doesn't matter. Matt.
Author: Norman C Corrin
Posted: Fri 19th May 2006, 17:06
Joined: 1981
Local Group: Beds, Bucks and Northants
Garfield, don't mince words my friend say what you mean!
Author: Garfield & Helen Southall
Posted: Fri 19th May 2006, 15:41
Joined: 1991
Local Group: Merseystride
It matters when I feel the route may have been wrongly measured, as on the last Calderdale Hike. If I seem to be taking longer than expected to do an event it's good to know that the extra 4 miles and 3000 ft equate to at least 3 hours via Naismiths rule !! I tend to use the altimeter in my watch, rather than my GPS, during an event. It tells me how much further I have to climb up this bl**dy hill !! - Garfield
Author: Norman C Corrin
Posted: Fri 19th May 2006, 12:10
Joined: 1981
Local Group: Beds, Bucks and Northants
Matthew & Jane, good point. Height climb may be useful when taking part in an event in mountainous areas but on the pretty flat Daffodil Dawdle will you be able to notice?
Author: Matthew Hand
Posted: Thu 18th May 2006, 22:12
Joined: 2001
Local Group: Mid Wales
I appreciate this is a serious question, and nobody is more qualified to answer it than Chris.

But I pose another question .... " Does it matter"? Obviously guidelines are needed on all events, so entrants can assess fitness, times etc. for the walk. But why become obsessed by the minutiae of figures, such as: distance to the nearest meter, overall ascent/descent? Surely these are meaningless figures compared to the overall enjoyment of the event? The more technology advances, the more we embrace it and the more we become obsessed by it. Just one question, is a walk better for knowing that you climbed an extra 50 ft over 30 miles?
Posted: Thu 18th May 2006, 21:48
Joined: 1972
Hi,
The eTrexVista instrument relies on a barometer sensor to measure elevation and not on satellite data so presumably it is liable to all idiosyncrasies that effect that method of measurement. The advantage over GPS triagulation(or should it be quadangulation) is that atmospheric pressure is measured and so you draw meteorologiclal inferences from the data displayed. But, as you have found, you will also acquire spurious ascents due to pressure variations caused by wind pessure on a breezy day. Interestingly in altimeter mode you can continue to receive valid data if for any rerason you lose satellite data.
Author: Tony Willey
Posted: Sun 9th Apr 2006, 22:22
Joined: 1989
Local Group: Lakeland
Following up on Geoff Saunders' post on the Calderdale hike thread, my belief is that GPS height gain is often substantially overstated, by more than can be accounted for by the tiddly bits that contour counting misses. My unscientific observation is that it may be worse on windy days. Does the mechanism pick up pressure changes from wind buffeting and interpret these as height changes? My Etrex Summit recorded 500 feet of height gain on a circuit of Brothers Water one windy day!

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