Poor Elevation Gain Accuracy - Garmin Instinct

Info on gear, conditioning, and preparation for hiking/climbing.
Forum rules
  • This is a mountaineering forum, so please keep your posts on-topic. Posts do not all have to be related to the 14ers but should at least be mountaineering-related.
  • Personal attacks and confrontational behavior will result in removal from the forum at the discretion of the administrators.
  • Do not use this forum to advertise, sell photos or other products or promote a commercial website.
  • Posts will be removed at the discretion of the site administrator or moderator(s), including: Troll posts, posts pushing political views or religious beliefs, and posts with the purpose of instigating conflict within the forum.
For more details, please see the Terms of Use you agreed to when joining the forum.
User avatar
Ed_Groves
Posts: 142
Joined: 6/6/2019
14ers: 25 
13ers: 11
Trip Reports (4)
 

Poor Elevation Gain Accuracy - Garmin Instinct

Post by Ed_Groves »

I was in Colorado two of the last three weeks hiking some 13ers and 14ers. Previously, I have noticed an approximate 200 feet inaccuracy on the low side in the elevation gain indicated so I don't expect perfection from this, or any watch. But on some of my hikes, it was really off. As an example, I hiked Father Dyer's East ridge to the summit, and then over to Crystal Peak A and back down to the basin on the Crystal Peak trail. Once that hike was completed my Instinct indicated I had gained just 2694 feet of elevation. The route description on this site shows that the east ridge of Father Dyer alone is 2700 feet of elevation gain. I checked a few other blogs and websites and found reported elevation gains for both peaks of 3100 to 3371 feet. Also, I find that every time I return from Colorado to Kansas City the elevation is about 300 feet above what it is supposed to be and I have to recalibrate it.

Has anyone else ran into this problem with this watch? Should I maybe recalibrate it when I arrive at my lodging, or maybe at the beginning of every hike? I don't mind being off by a couple hundred feet but three hundred or more seems to be a little bit much. Otherwise, I love the watch and all of its features.
"Education is the process of moving from cocksure ignorance to thoughtful uncertainty." (Utvich)
User avatar
LetsGoMets
Posts: 394
Joined: 9/9/2012
14ers: 58  5 
13ers: 132 6
Trip Reports (2)
 

Re: Poor Elevation Gain Accuracy - Garmin Instinct

Post by LetsGoMets »

Ed_Groves wrote: Sat Sep 11, 2021 4:26 pm I was in Colorado two of the last three weeks hiking some 13ers and 14ers. Previously, I have noticed an approximate 200 feet inaccuracy on the low side in the elevation gain indicated so I don't expect perfection from this, or any watch. But on some of my hikes, it was really off. As an example, I hiked Father Dyer's East ridge to the summit, and then over to Crystal Peak A and back down to the basin on the Crystal Peak trail. Once that hike was completed my Instinct indicated I had gained just 2694 feet of elevation. The route description on this site shows that the east ridge of Father Dyer alone is 2700 feet of elevation gain. I checked a few other blogs and websites and found reported elevation gains for both peaks of 3100 to 3371 feet. Also, I find that every time I return from Colorado to Kansas City the elevation is about 300 feet above what it is supposed to be and I have to recalibrate it.

Has anyone else ran into this problem with this watch? Should I maybe recalibrate it when I arrive at my lodging, or maybe at the beginning of every hike? I don't mind being off by a couple hundred feet but three hundred or more seems to be a little bit much. Otherwise, I love the watch and all of its features.
Garmin makes great watches, but the barometer leaves something to be desired. Generally it will drift and be off a few hundred feet on climbs regardless of it you calibrated it before (or even during an activity as some watches can do). Just something to deal with unfortunately. Use the GPS elevation where possible (or both)., but a barometer enabled watch uses the barometer elevations for all its calculations (thus your Garmin Connect activities are always going to be off elevation wise). I've owned 3 barometer enabled Garmin's and have always had the same issues. (Currently using a Fenix 6). No experience with other watch brands.
User avatar
yaktoleft13
Posts: 426
Joined: 4/17/2017
14ers: 58  15 
13ers: 262 22
Trip Reports (21)
 

Re: Poor Elevation Gain Accuracy - Garmin Instinct

Post by yaktoleft13 »

My Garmin Fenix 5 rarely reads close to the correct elevation, but oddly enough is always pretty accurate for total gain at the end of the days my Garmin etrex 20, however, usually nails elevation to within 10 feet. The watches are so useful for many things, but unless I truly climbed to 15,200 in Colorado, altitude isn't one of them. One of the reasons it so worth carrying a dedicated gps unit
User avatar
justiner
Posts: 4396
Joined: 8/28/2010
14ers: 58  8 
13ers: 138
Trip Reports (40)
 
Contact:

Re: Poor Elevation Gain Accuracy - Garmin Instinct

Post by justiner »

Calculating altitude based on barometric pressure is more accurate than calculating it by GPS because lots of difficult geometry I'll hand wave. If you're in a plane, your altitude is being calculated via barometric pressure.

There's also databases that have calculated elevation based on coords. If your watch says one elevation gain/loss total, and then Strava tells you something different, Strava is probably using a database, and throwing out the barometric pressure.

And actually calculating elevation gain/loss from a track is also not so straightforward:

Good read:

https://www.gpsvisualizer.com/tutorials ... _gain.html

I went down a huge rabbit hole about this, and noted a weirdness in Caltopo, which they responded by fixing the issue!

https://justinsimoni.com/2021/05/12/got ... gain-loss/

Anyways, finding elevation of any random coord is an inexact science, and total gain loss is an estimate.
User avatar
nyker
Posts: 3231
Joined: 12/5/2007
14ers: 58 
13ers: 25
Trip Reports (69)
 

Re: Poor Elevation Gain Accuracy - Garmin Instinct

Post by nyker »

I I haven't used that specific Garmin model but I use older replaceable battery powered Suunto T6D and T6C watches and while the altimeter and vertical gain and descent is usually fairly accurate within 50-100 ft I do usually have to recalibrate it often at the trailhead then they're fine.
User avatar
martinleroux
Posts: 299
Joined: 4/6/2012
14ers: 28 
13ers: 23
Trip Reports (2)
 

Re: Poor Elevation Gain Accuracy - Garmin Instinct

Post by martinleroux »

LetsGoMets wrote: Sat Sep 11, 2021 5:41 pmGarmin makes great watches, but the barometer leaves something to be desired.
Garmin's altimeters are no better or worse than anyone else's. They're all very accurate at measuring barometric pressure (that's all they do, really), but whether or not a pressure reading translates into an accurate elevation reading depends on the vagaries of current atmospheric conditions. All barometric altimeters translate barometric pressure into elevations using a standardized formula published by the Int'l Civil Aviation Organization (ICAO). However, this formula is based on idealized assumptions that are routinely violated in practice. In particular, in warm summertime conditions the ICAO formula can easily underestimate elevation gains by roughly 50-100' for every 1,000' of gain since the altimeter was calibrated. If you're climbing a peak with a 3,000' net gain, it shouldn't be a surprise if your barometric altimeter under-reads by 200-300' at the summit.

There's nothing that manufacturers can do to correct for this, because it would require information about the temperature profile of the column of air above your head. A portable altimeter can't measure this.
justiner wrote: Sat Sep 11, 2021 6:57 pmIf you're in a plane, your altitude is being calculated via barometric pressure.
That's true, but somewhat misleading. In general, pilots don't care about elevation in absolute terms. What they really care about is (a) avoiding mid-air collisions and (b) ensuring that altimeter readings converge on actual elevation as they come in for a landing. An pilot doesn't really care if an altimeter under-reads the elevation above the ground by 5-10%, so long as all other aircraft in the vicinity are equipped with altimeters that behave in exactly the same way.
User avatar
tlerunner
Posts: 172
Joined: 9/1/2008
14ers: 27 
13ers: 57
Trip Reports (2)
 

Re: Poor Elevation Gain Accuracy - Garmin Instinct

Post by tlerunner »

My Garmin way overestimates my elevation gain. I always adjust after uploading to Strava. It comes up with a more realistic number.
User avatar
Reg0928
Posts: 174
Joined: 8/17/2016
14ers: 58 
13ers: 253 2 11
Trip Reports (0)
 
Contact:

Re: Poor Elevation Gain Accuracy - Garmin Instinct

Post by Reg0928 »

My Instinct swings by a couple hundred feet in the high alpine as well. I calibrate it before every hike, run, or mtb ride.

Garmin Connect has a feature to adjust the elevation profile based on topo map data, but you have to be on a computer to access it. I haven't found a way to do it on the app. Strava has an option to adjust based on topo data as well, and it can be done on the app.

The watch is usually really accurate and consistent for all my runs and mtb rides, it just seems that all the pressure changes in the high alpine coupled with the large amounts of gain throw it off a bit. While I'm hiking I usually just take the number with a grain of salt, knowing that it's probably a little higher than actual.

When I get the hike uploaded to my phone I adjust it based on the topo and call it good. I'm usually just looking for a reasonable ballpark on my what I've gained anyway.
User avatar
martinleroux
Posts: 299
Joined: 4/6/2012
14ers: 28 
13ers: 23
Trip Reports (2)
 

Re: Poor Elevation Gain Accuracy - Garmin Instinct

Post by martinleroux »

tlerunner wrote: Sun Sep 12, 2021 9:27 am My Garmin way overestimates my elevation gain. I always adjust after uploading to Strava. It comes up with a more realistic number.
But how would you know which one is "more realistic"? As Justiner points out, there's no standard definition of elevation gain. The more precisely you try to measure every little up and down, the greater the apparent gain. It's like trying to measure the length of a coastline; there's no right answer.

As an illustration of the problem, here's something I posted a few weeks ago on another thread. These are my reported elevation gains for the 2021 San Juan Solstice race, all based on the same GPX file recorded by a Garmin Fenix 5X:
  • Per the device itself: 11,457' (using barometric elevations). This is almost certainly an understatement, because the barometric elevation at the course highpoint understated the actual elevation by a couple of hundred feet.
  • Garmin Basecamp: 11,742' (using barometric elevations as recorded by the device)
  • Garmin Basecamp: 12,524' (using a Digital Elevation Model)
  • Strava: 12,111' (using a DEM)
  • CalTopo: 13,292' (using a DEM)
So, which one is "correct"? You tell me!
User avatar
Ed_Groves
Posts: 142
Joined: 6/6/2019
14ers: 25 
13ers: 11
Trip Reports (4)
 

Re: Poor Elevation Gain Accuracy - Garmin Instinct

Post by Ed_Groves »

martinleroux wrote: Sat Sep 11, 2021 10:31 pm It shouldn't be a surprise if your barometric altimeter under-reads by 200-300' at the summit.
I agree that 200 to 300 feet off after approximately 3000 feet of elevation gain is acceptable with a barometric altimeter. I can live with that. My Garmin Instinct measured around 5900 feet on the Harvard - Columbia Traverse which is only 200 feet lower than the 6100 shown on this site, or 3.3 percent off of that figure. That is negligible.

However, in the example from the original post, the same watch gave me 2694 feet on a loop that was close to probably 3200 feet. (Figures from sites I have looked at seem to hover around 3200 to 3300 feet with outliers of 3100 and 3500 on the low and high ends respectively. Of course who really knows, right? 🙂). So my watch is 506 feet under the 3200 figure which is 15.8 percent. This site shows the first mountain I climbed as 2700 feet and my watch didn't even reach that for both mountains. Maybe barometric conditions were just right on this day to create measurement issues.
Last edited by Ed_Groves on Mon Sep 13, 2021 5:15 am, edited 1 time in total.
"Education is the process of moving from cocksure ignorance to thoughtful uncertainty." (Utvich)
User avatar
justiner
Posts: 4396
Joined: 8/28/2010
14ers: 58  8 
13ers: 138
Trip Reports (40)
 
Contact:

Re: Poor Elevation Gain Accuracy - Garmin Instinct

Post by justiner »

These are hard questions to answer without looking at the track. Perhaps one of the issues with a watch is that, to save battery life, the recording intervals between each point is a minute - or even 5 minutes, rather than every few seconds. Then the problem doesn't necessarily have anything to do with the barometric pressure being read incorrectly (or the barometric pressure changing drastically), it's just that the algorithm is doing its best with the information gathered.

Here's a similar example: the Elbert NE Ridge GPX on this site is only 175 points, for a 4.3 mile route. So one point for every 130 feet of distance traveled. Is that going to be super accurate? I can see a few hundred feet being "forgotten" here and there.

There's also the issue of perhaps the base GPX is under-reporting "true" elevation gain, and your device is over-reporting it. Then, the % diff between the two would be wider than you would suppose.
User avatar
bdloftin77
Posts: 1090
Joined: 9/23/2013
14ers: 58  1 
13ers: 58
Trip Reports (2)
 

Re: Poor Elevation Gain Accuracy - Garmin Instinct

Post by bdloftin77 »

justiner wrote: Sat Sep 11, 2021 6:57 pm My guess is that GPSVisualizer is really leaning hard on its horizontal noise filter. The docs mention being able to adjust this, but I don’t see the option on the initial form – so it may not be something available in the web-based app. I’ll leave that mystery here for someone else to solve.
Hey Justin, in your blog you mentioned not being able to find the horizontal distance filter online. Unfortunately the "Make a Profile" tab doesn't give this option. However, any of the tabs on the left do give that option. So it looks like you can filter horizontally, but you just have to do that first, save as a kml (for example), then bring that track into the Make a Profile tab to adjust vertically.

Thanks for the links! That was really interesting.
GPSVisualizer.jpg
GPSVisualizer.jpg (27.44 KiB) Viewed 3965 times
GPSVisualizer2.jpg
GPSVisualizer2.jpg (174.54 KiB) Viewed 3965 times
Post Reply