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SW version 24.19 gradient issue

chfreund38
6 months ago

Hello,

With the latest FW release (24.19), I'm facing a severe issue with grade (percentage) : The slope values displayed by the device are incorrect.

For example, on a severe slope, gradient values of 1 or 2% are displayed instead of 9 to 10%, and sometimes even negative values are displayed ..... This was not happening with previous FW version ....

This happens whatever the speed is during the climb .

Despite this issue altitude values remain correct, only gradients are wrong.

Seems really like a software bug ???

  • 0 6 months ago

    Maybe showing Wahoo vs Garmin will help better to understand what b..it grade is displaying Garmin 

    photos.app.goo.gl/MYnwYrVGQqtotFwk9

  • 0 6 months ago

    Agreed. This is a bug. In my case I was on a long ride and it went from reporting accurate gradient to 1% or 2% somewhere around hour 16. Elevation was still reporting correctly so it was not a barometer problem. 

  • 0 6 months ago

    Yes, it seems like a software bug. My girlfriend and I both have 1040S units and we experienced the same 1% to 2% readings while climbing double digit climbs. The altitude gains are coming up correctly. But sometimes the grade readings are correct. Pretty random but frustrating.

  • 0 6 months ago

    I think most will agree that there's an issue with gradient on the 1040, and this seems to have been introduced in one of the 24.** releases. (I don't use gradient a lot, and first noticed it when riding in a hillier region about three months ago). It's been suggested that it's hardware-related, but notwithstanding the limitations of the device, it can't be, really, because it used to work much better.

    It would probably be worth referring to this post on the beta forum. I haven't checked the hypotheses, but it sounds feasible to me, and given that elevation still seems to wok reasonably well, and that ClimbPro (when it uses Garmin's climb database) is also pretty awful I'd say it's probably the answer. Shame it's been done, because unless the database is improved MASSIVELY I can't see how it will ever work as well as using barometric pressure. My guess (??) is that it was an attempt to overcome the gradient lag issue. 

    24.15 - Gradient just GNSS based and altitude - Edge 1040 Series - 24.xx Bug Reports - Edge 1040 Series - Public Beta Bug Reports - Garmin Forums

  • 0 6 months ago in reply to simondaw

    About grade: I found out that grade was completely decoupled from the altimeter, it was solely GNSS based. How: After switching GNSS completely off, grade stopped working, i. e. remained on zero. @Garmin: Why? No wonder it's not working reliably anymore.

    Well, the grade was always (partly) GNSS based, here is why: it checks the your current altitude and GPS position, you move a bit (~50m), you have a new altitude and new GPS position, so the edge divides the difference between altitudes with the difference between the positions and tadam, you've got the grade 

  • 0 6 months ago in reply to pxl

    Yes, absolutely. Makes the methodology used to establish hs point a bt suspect, doesn't it? However, I still think he may be right; after all, a lot of people (including me) have found that elevation has suffered no obvious reduction in accuracy, whereas grade is now all over the place. The theory proposed would stll fit this, even though his "proof" is clearly flawed.  

  • 0 6 months ago in reply to pxl
    pxl said:
    Well, the grade was always (partly) GNSS based, here is why: it checks the your current altitude and GPS position, you move a bit (~50m), you have a new altitude and new GPS position, so the edge divides the difference between altitudes with the difference between the positions and tadam, you've got the grade 

    Wouldn't that only be the case when no speed sensor is used? Before the 24.xx firmware upgrade (which went hand in hand with the 11.00 GPS firmware update - that's why downgrading didn't work) I still had gradient riding through tunnels without any GPS signal.

  • 0 6 months ago in reply to OliverS73

    It would be absurd if only the GPS elevation were used for the gradient calculation, even though a barometer chip is present. And I can't believe that either. But what makes me think: if you use a speed sensor and switch off GPS, there is no longer a gradient display. Why is that?

    https://forums.garmin.com/sports-fitness/cycling/f/edge-1040-series/385903/elevation-graph-is-completely-wrong/1839068#1839068

  • 0 6 months ago in reply to mcinner1

    Because we guess it's not the GPS elevation that is used currently but the gradient that is stored in the very imprecise map and that needs the current GPS position and direction.

    By the way I don't have this problem because I use the DIY IQ app from hundsmiachn that calculates the gradient correctly with elevation changes divided by distance changes over a time period by my choice.