Garmin 500 or iphone for accuracy

pmcclure

Some friends did a route last week, 12.2 miles with 2152ft climbing using strava on an iphone. I've just done exactly the same route but only done 9.7 miles and 1831ft climbing using my garmin, then transferring it to starva. I know this part of the forum is road/general, but the route was done off road.

Which is more likely to be the more accurate, Garmin or iphone?

BrandonA

Have you plotted the route on a web site to see how long they thing the route is? One short ride doesn't really prove anything.

I don't trust elevation on any device. The joy of both Garmin Connect and Strava is that you can recalculate the elevation. I suspect neither would be very close to the actual amount.

Silly Old Hector

Also check the Garmin autopause feature setting. It can pause at low speeds, missing out distance.

As above, plot route on suitable software and compare.

navrig2

That's too big a difference to be device related. Probably too slow a speed on a steep section to register movement.

markhewitt1978

Go to the Strava route planner and plot the route out That's too big a difference to just be measurement error.

pmcclure

Silly Old Hector wrote:

Also check the Garmin autopause feature setting. It can pause at low speeds, missing out distance.

Yes the autopause was on. Will turn it off. The garmin is used for both road use and MTB use. (Some slow speeds are the norm offroad)

iron-clover

Over longer rides the Garmin will probably be more accurate for elevation as it has an inbuilt barometer. It does get confused when the temperature or pressure changes (you'll often see an elevation cliff after a cake stop for example) but other than that is pretty good.
The iphone will be using the elevation supplied from google maps or similar, which uses a US survey group's data. Outside the US the elevation can have a relatively large inaccuracy. If they used OS data for the UK then it would be more accurate.

markhewitt1978

iron-clover wrote:

Over longer rides the Garmin will probably be more accurate for elevation as it has an inbuilt barometer. It does get confused when the temperature or pressure changes (you'll often see an elevation cliff after a cake stop for example) but other than that is pretty good.
The iphone will be using the elevation supplied from google maps or similar, which uses a US survey group's data. Outside the US the elevation can have a relatively large inaccuracy. If they used OS data for the UK then it would be more accurate.

The iPhone 6 also has a barometer so there's no reason to believe it would be less accurate.

southdownswolf

markhewitt1978 wrote:

iron-clover wrote:

Over longer rides the Garmin will probably be more accurate for elevation as it has an inbuilt barometer. It does get confused when the temperature or pressure changes (you'll often see an elevation cliff after a cake stop for example) but other than that is pretty good.
The iphone will be using the elevation supplied from google maps or similar, which uses a US survey group's data. Outside the US the elevation can have a relatively large inaccuracy. If they used OS data for the UK then it would be more accurate.

The iPhone 6 also has a barometer so there's no reason to believe it would be less accurate.

Does Strava now support the barometer in the Iphone 6, as it didn't at the end of last year?

rafletcher

Barometric height readings do rely on a "base" pressure. Which changes quite a bit IRL, so only a guide (and why plane altimeters are reset to reflect the value at the airport they are departing from / arriving at).

stevie63

A colleague of mine uses their phone with the strava app and the rides look like a wiggly line kind of like they are weaving all over the road. This in turn makes all their rides slightly longer. I think it is because they keep their phone in a bag it means that the GPS is not as reliable. If your friends didn't have their phones mounted to their bars could this have been the reason for the extended distance?

southdownswolf

rafletcher wrote:

Barometric height readings do rely on a "base" pressure. Which changes quite a bit IRL, so only a guide (and why plane altimeters are reset to reflect the value at the airport they are departing from / arriving at).

Forgive my ignorance, but surely for bike riding purposes the barometric value will be fine as long as the Garmin etc doesn't re-calibrate itself mid ride? I can understand that a plane needs to be callibrated at the start as actual height needs to accurate, whereas on a bike it is just the change that is needed to reflect altitude gained/lost?

wongataa

southdownswolf wrote:

Forgive my ignorance, but surely for bike riding purposes the barometric value will be fine as long as the Garmin etc doesn't re-calibrate itself mid ride?

It depends whether the atmospheric pressure changes drastically mid ride which can easily happen due to weather.

keith57

All Garmin's need some time stationary before moving to calibrate their altitude (the ones with a Barometer anyway). With my old 700 this could take up to around 5 mins sometimes to get the altimeter to the right altitude. I used to put it on the bike switched on outside the house while I got ready. If security is an issue you can leave the Garmin somewhere it can see the sky to do the same thing.

All that's happening (so I believe) is it's working out it's height from weak triangulation from the satellites, and it can only do this properly when it's not moving. Because of changes in atmospheric pressure overnight it will always read differently to what it indicated the day before.

With the 800 onwards there is a menu setting to set the altitude manually at the start of a ride.

Even better, if you set a waypoint where you normally start (e.g. your home or hotel) and set the altitude correctly in the waypoint screen, (you need to check!), the altitude will automatically set to this height when you press the start button within range of the waypoint.

Our house, for example, I know is at 190m asl, so my home waypoint is set to this When I press the start button, regardless of what altitude the Garmin thinks it's at, it always changes to 190m asl. Simple.

On holiday in Calpe a few weeks ago I created a waypoint outside our hotel and set the altitude of the waypoint to 5m or so. So every morning after that, once some satellites had been 'seen', I would press the start button and the altitude was set to 5m automatially.

BTW I never pause or switch the thing off when riding - too often I've forgotten to switch it back on again after a cafe stop!! All the paused time, moving average, etc, is worked out in whatever programme you use to log and analise your rides, independently of what the Garmin screen is telling you.

markhewitt1978

southdownswolf wrote:

markhewitt1978 wrote:

iron-clover wrote:

Over longer rides the Garmin will probably be more accurate for elevation as it has an inbuilt barometer. It does get confused when the temperature or pressure changes (you'll often see an elevation cliff after a cake stop for example) but other than that is pretty good.
The iphone will be using the elevation supplied from google maps or similar, which uses a US survey group's data. Outside the US the elevation can have a relatively large inaccuracy. If they used OS data for the UK then it would be more accurate.

The iPhone 6 also has a barometer so there's no reason to believe it would be less accurate.

Does Strava now support the barometer in the Iphone 6, as it didn't at the end of last year?

It doesn't need application support. The Strava app just asks the phone what height it is at the moment and the phone returns a result.

southdownswolf

markhewitt1978 wrote:

southdownswolf wrote:

markhewitt1978 wrote:

iron-clover wrote:

Over longer rides the Garmin will probably be more accurate for elevation as it has an inbuilt barometer. It does get confused when the temperature or pressure changes (you'll often see an elevation cliff after a cake stop for example) but other than that is pretty good.
The iphone will be using the elevation supplied from google maps or similar, which uses a US survey group's data. Outside the US the elevation can have a relatively large inaccuracy. If they used OS data for the UK then it would be more accurate.

The iPhone 6 also has a barometer so there's no reason to believe it would be less accurate.

Does Strava now support the barometer in the Iphone 6, as it didn't at the end of last year?

It doesn't need application support. The Strava app just asks the phone what height it is at the moment and the phone returns a result.

I believe that the app automatically overrides the barometer in the iPhone 6 with Strava's own "corrected elevation", Strava needed to write into the software not to do this on the iPhone 6, however it had not been done at the end of last year.

markhewitt1978

I remember someone posted a comparison of the same ride done with an iPhone 5S (no barometer) and an iPhone 6 both using the Strava app and there were noticeable differences in the elevation profile, with the 6 being smoother.

Chunky101

In my experience the iPhone 6 is well out. Went out for a group ride in Majorca, after 70+ miles my fellow riders Garmins had all registered 7k feet of climbing and my iPhone 6 had registered over 12k feet. Good for the ego, not good for stat analysis.

southdownswolf

I know that at 31st December strava automatically ignored the barometric data from Apple. Smoother or not, it wasn't accurate. There has been an app update since then, but nothing mentioned allowing barometric elevation for the iPhone. Not sure about android app, but I think it is the same story.