Garmin elevations in crisis.
- Thread starter Milzy
- Start date
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fossyant
Ride It Like You Stole It!
- Location
- South Manchester
By much ?
N0bodyOfTheGoat
Über Member
- Location
- Hampshire, UK
On the activity webpage on Strava, click the "..." and "correct elevation" to have your log look reasonable.
- Location
- Inside my skull
If that if the only crisis in your life, first world problems…
nogoodnamesleft
Senior Member
Is everybody else using a Garmin 10x0 or are you comparing your 1040 with Wahoo/Bryton/Sigma devices?
I have always felt my Garmin overstates ascent/descent but that's always based on a few m ascent and then looking at what the Garmin ascent increases by and such low ascents will be subject to a fair variation and precision.
I have once had a real anomaly on measured ascent on my Garmin 1040 (might have been the 1050). Ascent way off but descent sensible and it must have been an anomaly as it was circular from home and invariable ascent is within a couple of meters of descent and on this occasion it was way different. Next ride it had been restarted and not happened again.
Checking against an online route is also not particularly useful as onling route creation/analysis necessarily has to use interpolation and from that some estimation so I always regard the figures they give as an index rather than a true height eg this rote is 300<x> and the alternative 600<x> and best I can say is the 2nd alternative is twice the ascent of the first.
OP
OP
Milzy
Legendary Member
Boiler was broken but now fixed. Fix the first world problems first & work on the bigger ones will be easier.
fossyant
Ride It Like You Stole It!
- Location
- South Manchester
Come and fix my fridge LED please. Ordered a new one !
- Location
- Inside my skull
Does it not come on when you open the door? Try closing the door to see if that works.
EckyH
It wasn't me!
- Location
- Nottuln, North Rhine-Westphalia
Garmin 1040 and other Garmin devices guess the elevation by atmospheric pressure: barometric height "measurement".
Therefore I don't trust them not as high as I could throw them.
E.
This.
Once everyone has done it the elevations should be similar. Pre-correction hundreds of metres difference is not unusual.
fossyant
Ride It Like You Stole It!
- Location
- South Manchester
I never really bother with what the device says, I only really look once it's uploaded, then the height corrections are done.
- Location
- Inside my skull
Atmospheric pressure derived is considered more accurate than GPS elevations. Only really a problem if you have a massive low or high pressure system moving rapidly across where you are.
nogoodnamesleft
Senior Member
But even that will be subject to algorithms used by Strava. Garmin Connect offers the same feature.
Online and computer (mapping) systems calculate a route ascent by looking at altitude along your chosen route or track. But they don't know the altitude at every point along your route so they have to interpolate between points nearby they do have the altitude for. Most use SRTM (Shuttle Radar Topography Mission) which provides altitude for a grid with between 100m and 30m spacing over much of the surface of the Earth but with constraints.
How useful interpolating points 100m apart depends on the landscape. Gentle long slopes, etc. it might work well but other areas eg with clifs and steep hills it is pretty poor. eg Look at an altitude profile online systems generate cycling up Eurovelo 6 through the Doubs valley in France. mHorrible and expect a few hard days ... except the path you take is right next to the river and pretty flat and level as you ride sometimes next to cliffs, sometimes more open areas with steeper hills both sides, etc.
Constraints and sources of error are eg the SRTM sensors detect the altitude of eg top of trees as their signal can't get to the ground so move from open ground into a forect along flat ground and SRTM will suggest you altitude has jumped by the height of the trees. But subsequent processing has removed some of these forest anomalies. But different grid spacings have been released at different times for different areas of the world and users of the data taken the updated data at their convenience (id atall).
TL;DR on device vs computer "corrected" have constraints and at best useful only for comparing different rides on different days ignoring the units eg today I did 300<whatevers> where yesterday <150<whatevers> to today was twice the ascent. Relevant number is "today twice the ascent".
fossyant
Ride It Like You Stole It!
- Location
- South Manchester
Life is too short to worry about such things TBH.
nogoodnamesleft
Senior Member
For me I find the ascent estimates in online route creation systems useful. Provided I stick with the same system (I use cycle.travel) when I create my route for tomorrow I can see the sort of ascent I might be getting. Sometimes I can add some via points to add a couple of miles distance and reduce the ascent a fair bit. Sometimes if I have no choice on terrain and my legs are suffering I might look for a campsite a bit closer to shorten the ride or if plenty of energy and terrain fairly flat maybe I look to go further.
But that only works if you stick to one site and you have the experience to know that when that site says 500<whatevers> what that means in practice over the ride.
Similarly with any system when touring the steep ascent systems can be useful where they tell you the points along your route there are "significant" climbs (and you can qualify "significant") Helps as for a few miles before getting to a steep ascent I'll take things a bit slower and easier so my legs are better able to manage the coming steep section.
