More Vista HCx Altimeter / Total Ascent problems

[AlunS]

Well, I thought the problems with the calculation of total ascent on my Vista HCx had been sorted out, but today I went on a hike with a calculated 800m or so of ascent, and the thing reported 1657m ascent, more than double.

 

Looking at the track log, I see myself in a few places jumping up and down 10m or so, several times in a row, while I'm actually standing still! The only thing I can think of is that it was a particularly windy day today, and I'm wondering whether that could have been the problem. I have the GPS in a case mounted high up on my rucksack strap, so it would be quite exposed.

 

So, does anyone know if the altimeter in the GPS would be particularly affected by the wind like this? If so, then in a windy place like Ireland, it renders the altimeter next to useless for this purpose.

[groth]

Well, I thought the problems with the calculation of total ascent on my Vista HCx had been sorted out, but today I went on a hike with a calculated 800m or so of ascent, and the thing reported 1657m ascent, more than double.

 

Looking at the track log, I see myself in a few places jumping up and down 10m or so, several times in a row, while I'm actually standing still! The only thing I can think of is that it was a particularly windy day today, and I'm wondering whether that could have been the problem. I have the GPS in a case mounted high up on my rucksack strap, so it would be quite exposed.

 

So, does anyone know if the altimeter in the GPS would be particularly affected by the wind like this? If so, then in a windy place like Ireland, it renders the altimeter next to useless for this purpose.

 

Hmmm....

 

I have a summit, a vista, a vista C and now a vista HCx. All have a barometric altimeter with the little hole in the back that leads to the pressure gauge. Never noticed a problem with the wind. However, I did get water on the little hole once. Not surprisingly, I got bogus altitude readings until it dried out.

 

(No, I didn't drop it in the toilet, it was on my handlebars on a fast downhill in the rain!)

 

If you like, you can email your track log and I'll try and see what my software gives for the total ascent.

 

groth

 

at

 

princeton

 

dot

 

edu

 

- Ed

[+julianh]

Well, I thought the problems with the calculation of total ascent on my Vista HCx had been sorted out, but today I went on a hike with a calculated 800m or so of ascent, and the thing reported 1657m ascent, more than double.

 

Looking at the track log, I see myself in a few places jumping up and down 10m or so, several times in a row, while I'm actually standing still! The only thing I can think of is that it was a particularly windy day today, and I'm wondering whether that could have been the problem. I have the GPS in a case mounted high up on my rucksack strap, so it would be quite exposed.

 

So, does anyone know if the altimeter in the GPS would be particularly affected by the wind like this? If so, then in a windy place like Ireland, it renders the altimeter next to useless for this purpose.

It's certainly plausible. Driving at 60 to 80 km/hr steady speed on flat ground, and opening and closing the windows in my car, will generate instantaneous apparent elevation jumps of the order of 5 to 10 metres, as the air pressure in the car equalises. Being blasted by wind gusts of similar speed could plausibly generate similar effects.

 

You could try keeping the GPSr in a pocket or inside a backpack, to see if that would "damp out" the air pressure changes in very blustery conditions.

 

(Just speculation by the way - I have not personally monitored the reported elevation under such conditions, and of course, your GPS reception may suffer when the unit is concealed in this way, although the "H" series models seem to be sensitive enough to give good reception under such circumstances.)