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Need GPS unit advice

Old 05-30-22, 09:35 AM
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bruce19
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Need GPS unit advice

I've been using Garmin units for 6-10 yrs. The first was an Edge 200 and a couple years ago an Edge 130 Plus. I typically use the Edge 130 and keep the Edge 200 as a backup. I like the simplicity and don't need a lot of the enhanced functions of some units. But, recently both units are giving me bad elevation data. I spoke with a Garmin rep about the 130 and reset it. It had been giving me very high readings. After the fix it worked perfectly for a few rides. Yesterday I did a 1300 ft. ride and it gave me 400 ft. The backup 200 read 800 ft. So, I'm looking for a unit that is fairly basic. Any suggestions or ideas about what I should consider?
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Old 05-30-22, 09:53 AM
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I cannot suggest anything or any manufacturer for reliable elevation. You would want a unit that has a barometric sensor as that supplements the GPS elevation, but really I'd say the elevation issues is the most common complaint about all the units and is a problem in general as GPS just cannot accurately measure elevation, its the very nature of how the signals get received from the satellites. Then you deal with how the assorted tracking apps deal with the data sent from the device and what they think they know in their database. And it varies wildly.
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Old 05-30-22, 10:05 AM
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Originally Posted by Steve B. View Post
I cannot suggest anything or any manufacturer for reliable elevation. You would want a unit that has a barometric sensor as that supplements the GPS elevation, but really I'd say the elevation issues is the most common complaint about all the units and is a problem in general as GPS just cannot accurately measure elevation, its the very nature of how the signals get received from the satellites. Then you deal with how the assorted tracking apps deal with the data sent from the device and what they think they know in their database. And it varies wildly.
I just attempted to reset my 130 and noted that the base elevation had shifted from 431 ft to well over 600 ft. The 431 ft is where my house is on a topo map. I had reset it to 431 about a week ago. Why it reset itself to 600+ is beyond me. I'm thinking there is a problem with the unit.
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Old 05-30-22, 12:29 PM
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I would want to know what happened to make the units suddenly act this way?

Are you able to calibrate the barometer in the 130+? Or check the calibration?

If you want to fix the problem with money, the barometers in Fenix watches are spectacular. Typical for me is about 3 feet error per thousand feet of gain. But all barometers drift and are vulnerable to atmospheric effects.
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Old 05-31-22, 01:23 AM
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Originally Posted by bruce19 View Post
I've been using Garmin units for 6-10 yrs. The first was an Edge 200 and a couple years ago an Edge 130 Plus. I typically use the Edge 130 and keep the Edge 200 as a backup. I like the simplicity and don't need a lot of the enhanced functions of some units. But, recently both units are giving me bad elevation data. I spoke with a Garmin rep about the 130 and reset it. It had been giving me very high readings. After the fix it worked perfectly for a few rides. Yesterday I did a 1300 ft. ride and it gave me 400 ft. The backup 200 read 800 ft. So, I'm looking for a unit that is fairly basic. Any suggestions or ideas about what I should consider?
I think if you go with a unit that has built in maps, it should accurately give you elevation data based on the map data. Units like the Wahoo Elemnt Roam or Bolt V2, or the Garmin Edge 530/830/1030. Or even the Hammerhead Karoo2. I think these all have built-in maps with elevation data in them. (double check each unit just to make sure).

The accuracy of the elevation data in the maps can vary from brand to brand. I thought I'd heard the Karoo2 elevation data (at least the grade %) can be off quite a bit. The Wahoo and Garmin units do a bit better I think. Most of these units also have a "climbing" function which shows metrics for a climb like which part you are on, the gradient, upcoming gradient, elevation covered, elevation remaining, etc.

Good luck.
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Old 05-31-22, 02:42 PM
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Originally Posted by Steve B. View Post
… in general as GPS just cannot accurately measure elevation, its the very nature of how the signals get received from the satellites.
It measures elevation/altitude the same way it measures geographic location. That is, your (the device) distance from the satellites.

Dan
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Old 05-31-22, 02:58 PM
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Originally Posted by _ForceD_ View Post
It measures elevation/altitude the same way it measures geographic location. That is, your (the device) distance from the satellites.

Dan
Here's what Garmin has to say on the issue. "It is not uncommon for satellite heights to be off from map elevations by +/- 400 ft"

Understanding the Accuracy of the GPS Elevation Reading | Garmin Customer Support
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Old 05-31-22, 03:47 PM
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GPS elevation is less accurate than GPS lat/lon for mathematical reasons. There's really no way around that. Barometric altitude is much better as long as the barometer is calibrated properly. Many bike computers automatically calibrate their barometers from GPS at the start of a ride, some do it continuously to addresses barometer drift.

Modern GPS units do a pretty good job with GPS altitude. It's rare in my experience for it to be off by more than 50 feet with a good lock.
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Old 07-02-22, 03:26 PM
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Originally Posted by _ForceD_ View Post
It measures elevation/altitude the same way it measures geographic location. That is, your (the device) distance from the satellites.
Yes, GPS elevation is determined the same way as GPS position. But elevation error will aways be higher than position error, due to the positions of the satellites.

It's a geometry problem — none of the satellites below the horizon are visible.
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Old 07-02-22, 04:25 PM
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Just use "Elevation Correction" in Garmin Connect until they stop messing with the GPS positions to confuse the Russians.
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Old 07-10-22, 10:31 AM
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I use a Lezyne Mega XL. From what I have read about them, they use a barometer (GPS - Elevation Data – Lezyne Customer Service and Warranty Support). I am at an elevation of 301 feet at home and I have my GPS unit consistently read between 297 and 303 ft.
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Old 07-10-22, 11:45 AM
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Originally Posted by maartendc View Post
I think if you go with a unit that has built in maps, it should accurately give you elevation data based on the map data. Units like the Wahoo Elemnt Roam or Bolt V2, or the Garmin Edge 530/830/1030. Or even the Hammerhead Karoo2. I think these all have built-in maps with elevation data in them. (double check each unit just to make sure).

The accuracy of the elevation data in the maps can vary from brand to brand. I thought I'd heard the Karoo2 elevation data (at least the grade %) can be off quite a bit. The Wahoo and Garmin units do a bit better I think. Most of these units also have a "climbing" function which shows metrics for a climb like which part you are on, the gradient, upcoming gradient, elevation covered, elevation remaining, etc.

Good luck.
My 1030 seems to be much more accurate than a friend's new Bolt. We did a 40+ mile ride a few weeks ago, and the 1030 showed +1200' which matched Ride with GPS, but the Bolt showed about 800'. Of course, he was coasting on the wings of angels while I was pedaling squares by the end so that may have played a part.
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Old 07-10-22, 11:51 AM
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My Garmin said 1,984 feet of elevation gain yesterday (over 2.75 miles!) but the topographic map and route database both say 2,000 exactly. That's a total disagreement of 16 feet, or less than 1% difference from the best source available.
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Old 07-10-22, 03:20 PM
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Originally Posted by maartendc View Post
I think if you go with a unit that has built in maps, it should accurately give you elevation data based on the map data. Units like the Wahoo Elemnt Roam or Bolt V2, or the Garmin Edge 530/830/1030. Or even the Hammerhead Karoo2. I think these all have built-in maps with elevation data in them. (double check each unit just to make sure).
Garmin uses a barometer to measure elevation and gain. They use map data to correct for devices that just have GPS. This suggests that the map data isn't as good.

Originally Posted by maartendc View Post
The accuracy of the elevation data in the maps can vary from brand to brand. I thought I'd heard the Karoo2 elevation data (at least the grade %) can be off quite a bit. The Wahoo and Garmin units do a bit better I think. Most of these units also have a "climbing" function which shows metrics for a climb like which part you are on, the gradient, upcoming gradient, elevation covered, elevation remaining, etc.
There are not many sources for world-wide elevation data. Most of the brands are likely using the same base data. They might be doing different things interpolating it.

Strava used actual rider data (most of which is probably based on barometers).
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Old 07-10-22, 03:22 PM
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Originally Posted by znomit View Post
Just use "Elevation Correction" in Garmin Connect until they stop messing with the GPS positions to confuse the Russians.
Garmin provides this for devices that don't have barometers (or have broken ones). This suggests that Garmin sees barometric data as better than map data.
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Old 07-10-22, 03:23 PM
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Originally Posted by Seattle Forrest View Post
My Garmin said 1,984 feet of elevation gain yesterday (over 2.75 miles!) but the topographic map and route database both say 2,000 exactly. That's a total disagreement of 16 feet, or less than 1% difference from the best source available.
That's a lot of gain over a very short distance. It's not surprising that both are close.
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