Stupid altimeter in GPS

Let’s be honest here. What’s the point of having a barometric altimeter in your GPS? Specially if you live in Taipei and around.

I don’t know how inaccurate GPS technology is for calculating your current altitude, but it can’t be worse than a barometer. Come on, yesterday I leaned my bike against a wall for about 25 minutes and when I took the bike again, apparently it was in a parallel reality, 200 meters above me.

It doesn’t make any sense. I don’t know why companies keep including barometers in GPS units. Is it perhaps that there are other more expensive and reliable devices in which the barometer does work, and Garmin and Garmin-like companies include it too, so that your GPS looks more professional?

Weather conditions vary greatly, even during the same ride. Road cyclists, at which these devices are target (mainly), climb mountains (because it’s in their stupid nature) and surprise, there’s a number of factors that alter the air pressure in the mountain, so the GPS gives you absurd reads.

So… anybody, please explain me why companies keep using barometers instead of GPS (+GLONASS) for telling your altitude. I don’t get it. specially useless for rides that involve valleys, mountains and coast. GPS can not be worse than barometric altimeters… can it?

1 Like

Are you just upset that you reported a wrong elevation gain onto Strava? I know I would be.

Honestly, how I see it is, barometric altimeter is more accurate for elevation than GPS.

However, from recent research and asking around, any water getting into your unit through the USB charger or any other cracks and your altitude can be thrown off by a few hundred (even thousands of meters).

My ride two Sundays ago was a race and everyone knew total elevation gain was 2200m, but everyone’s Garmin reported either 1400m or 3000m. Surprisingly, it did not happen last year. I think it’s time to bring in the Garmin for maintenance.

That’s interesting. Wrong data update?

Nope, Garmin is old and has been taking beatings from rides in the rain. The rubber cover over the USB input doesn’t do the greatest job of blocking water being spit into the unit.

It’s too bad Garmin changed its policy recently. Used to be free repairs and replacements even if the unit was over warranty period. Now they charge =(

AFAIK GPS altitude is hopelessly inaccurate, and varies from moment to moment depending on where the satellites are at. Could be anywhere up to +/-50m, it seems.

I’m sure that could be improved upon by adding GLONASS data - there are lots of receivers out there that support both these days - but presumably it’s cheaper to incorporate a barometer instead :slight_smile:

Probably GPS is not very reliable when it comes to altitude, but the barometer sensor is useless cycling around Taipei :frowning:

@finley, nowadays many phones and tables support GLONASS too.

So get a phone that uses GLONASS instead

If that were true, everyone’s altitude would be completely screwed up in Taipei and you know that’s not the case.

You rode a few weeks ago and got stuck in rain right? Any kind of water damage to the interior of your unit will completely f up the unit.

No, it’s not because the rain. It’s something about atmospheric changes, which happen a lot around Taipei, and affect every single barometric sensor.

I went out one day before you and had zero issues with total elevation gain. I remember that weekend having very similar weather reports too.

I’d like to see the numbers and stats behind this…

You can google it. Barometric sensors meter… pressure. And pressure can change any time.

That I knew and I now see I had a lost in translation moment when reading your post.

You meant, the atmospheric pressure effects barometric sensors.

I read, the atmospheric pressure caused all cyclists’ barometric sensors to be off in Taipei on that day.

barometric sensors meter atmospheric preassure. If there are changes in the atmosphear, in the air pressure, of course that affects every single unit with a barometric sensor. It’s like if you had a metereological sensor in your garden for collecting water and… it rains. That thing will read that there’s water and how much. And if I pour a glass of water, it will also be “affected by it”, because it collects water. Same for barometric sensors: they are designed for that. The problem is to be exposed to pressure changes because the place were you live or ride has lots of weather changes. These reads have to be taken with a pinch of salt.

BTW, the other day I read that the barometric sensors that are used in aircrafts, are being continously adjusted during the flight with some other data. Why so? because of air pressure fluctuations affect the read from the sensor.

From Wikipedia:

Because barometric pressure changes with the weather, hikers must periodically re-calibrate their altimeters when they reach a known altitude, such as a trail junction or peak marked on a topographical map

A very comprehensive post on this:

it is an interesting topic, but it’s almost 6:00 AM here and I feel like to take a shower and go to ride… the only problems are cold and dark! :frowning: