# GLONASS vs Galileo



## Sparticus (Dec 28, 1999)

My Garmin 530 offers three satellite options:

GPS 
GPS + GLONASS 
GPS + Galileo 
 I've had my Garmin 530 for a few weeks now and like it. This is my 3rd or 4th Garmin and all my units have recorded dissimilar distances over identical courses, some differing only slightly and some more significantly. I ride with many others who use Garmins as well and our units always vary for distance/gain, sometimes insignificantly and sometimes quite a bit. For example on yesterday's ride, my 530 recorded just a hair over 14 miles and my GF's Garmin 520 (the one that I gave her when I got my new 530) recorded nearly 15 miles even though we rode exactly the same route.

Nearly 1 mile in 15. That's significant. Weird.

On yesterday's ride my Garmin 530 was set to employ GPS + GLONASS -- so was my GF's 520.

My home turf is Oregon's Cascades Range & foothills which include some serious terrain including high ridges, deep forests and canyons. In the past (using my old 520) I always ran GPS + GLONASS but now with the 530 I have a third option: GPS + Galileo.

Which supplementary satellite system (if any) will provide optimum linear distance accuracy -- GLONASS or Galileo?

TIA,
=sParty


----------



## Lone Rager (Dec 13, 2013)

I don't think there's any systematic or consequential difference between them for our purposes. Supposedly, the more you use, the more satellites are being received which will somewhat improve accuracy. Best thing, especially when riding tortuous mtb trails, is to use a wheel sensor, which is why Garmin has provisions for using them. 

Many suggest using 1/sec data recording rather than smart recording. I use a wheel sensor with smart recording and GPS only and get good consistent distances and speeds.


----------



## Sparticus (Dec 28, 1999)

Lone Rager said:


> I don't think there's any systematic or consequential difference between them for our purposes. Supposedly, the more you use, the more satellites are being received which will somewhat improve accuracy. Best thing, especially when riding tortuous mtb trails, is to use a wheel sensor, which is why Garmin has provisions for using them.
> 
> Many suggest using 1/sec data recording rather than smart recording. I use a wheel sensor with smart recording and GPS only and get good consistent distances and speeds.


Thanks, LR. I should have mentioned that in the case above, both bikes were outfitted with speed sensors and set to 1/sec data recording.

For the heck of it I'm going to try GPS + Galileo to see if the two units yield more similar distance measurements. If they don't, I'll consider resetting to GPS + GLONASS.

As for data recording interval, I better delve down that rabbit hole. I vaguely recall hearing that 1/sec recording is more accurate while smart recording uses less battery but my recollection is years old and might not be as accurate as i wish it was. ?

Thanks again,
=sParty


----------



## Le Duke (Mar 23, 2009)

Galileo is more accurate than GLONASS. By quite a bit.


----------



## Sidewalk (May 18, 2015)

I recently did a race with minimal tree coverage (compared to places many other people ride) and was surprised when my satellite only distance was nearly identical to my friends who had a speed sensor.

So I think your results might vary.


----------



## Sparticus (Dec 28, 1999)

Sidewalk said:


> I recently did a race with minimal tree coverage (compared to places many other people ride) and was surprised when my satellite only distance was nearly identical to my friends who had a speed sensor.
> 
> So I think your results might vary.


Agreed. In fact, my experience supports your assertion. Whenever I'm riding in open terrain with uncluttered exposure to the heavens, my speed sensor proves superfluous. However this doesn't happen very often in places I typically ride -- usually there's too much forest canopy. Steep canyon walls and adjacent high ridges can block reception as well, but these are lesser problems in these parts.
=sParty


----------



## Sidewalk (May 18, 2015)

On the other end of the scale, I hiked the Zion Narrows a few months back and ended up with 16 miles, but I mapped it out later at 10 :lol:

https://www.strava.com/activities/3610101990


----------



## Harold (Dec 23, 2003)

The main advantages to GLONASS are that it has better coverage in more northern latitudes and that signal acquisition is a bit faster. If I was in Alaska or northern Canada, I'd be using it in preference to Galileo (if given the choice). I use GPS+GLONASS now simply because it gives me more satellites to choose from, as the southern Appalachians where I ride have steep valleys and heavy forest cover, so I'll take whatever satellites I can get.

Yes, open trails, in open country will oftentimes do fine with no wheel sensor. The wheel sensor becomes essential to getting an accurate distance when things get dicey. IME, the absolute biggest factors are with challenging reception and extremely twisty trails. Because I deal with both (not necessarily every time, but often enough), I use a wheel sensor and won't ever ride without one. Even on my road bike, one of my favorite winter rides has lots of tunnels. Even if the GPS don't lose the signal outright, it wanders all over hell and without a wheel sensor, it'll add SUBSTANTIAL distance.

There's a couple things going on with recording interval. Certainly if you don't have a wheel sensor, the more frequently you drop a point, the better the distance recording will be through corners. This becomes moot if you have a wheel sensor. The other thing where recording frequency becomes an issue is with mapping accuracy. Not sure if Garmin has updated its algorithm for smart recording, but in the past, I've noticed a reduction in accuracy of the track when using it. If you're trying to map a trail for any official purpose (for the park as a volunteer project, or for Trailforks/MTBProject), this can be important. This can actually play a role with segment matching on Strava, too. On straighter/open trails with fewer tight turns, it's unlikely to be a big problem. But again with the twisty trails, the discrepancies can result in not matching up. There's also the error introduced by where a point is recorded relative to the start and finish of the segment. That can really add a lot of inconsistency with segment times.

Now, back to the original question. If both computers are using wheel sensors and yet they have a discrepancy of 1 mile in 15, there are two things I'd be checking. First, I would check to see that both sensors have fresh batteries. When they begin to die, these discrepancies can start to pop up before you get any notification on the computer about low sensor batteries. And then of course, you won't get anything if a battery is totally dead. I encounter this situation from time to time with my wife and I's computers. If both of the batteries are good, then I would look at the calibration. Sometimes the auto calibration is fine, but it doesn't always calibrate well. This is why there's a provision for a manual calibration.


----------



## Sparticus (Dec 28, 1999)

Harold said:


> I encounter this situation from time to time with my wife and I's computers. If both of the batteries are good, then I would look at the calibration. Sometimes the auto calibration is fine, but it doesn't always calibrate well. This is why there's a provision for a manual calibration.


Thanks, Harold. Both batteries are good. I've done manual calibration before but I have five different wheels with dedicated sensors on each wheel and I'm certain I didn't measure them all... more like one or two and that was done long ago. I doubt sensor measurements carry forward from one Garmin head unit to the next so I should make the effort to measure them all and input the results. Thanks again for the suggestion.
=sParty


----------



## Harold (Dec 23, 2003)

Sparticus said:


> I doubt sensor measurements carry forward from one Garmin head unit to the next so I should make the effort to measure them all and input the results.


Depends which sensor you've got. If you have the older ones like I do, then no. Garmin does sell a new sensor that does have a small onboard memory, though.

https://buy.garmin.com/en-US/US/p/pn/010-12843-00


----------



## Catmandoo (Dec 20, 2018)

Correct me if I'm wrong but I thought that a Garmin unit using a wheel sensor will automatically default to the distance being recorded by the sensor and will ignore the GPS data. Thus it won't matter which combo of the 3 GPS systems you set it to. 

This of course, assumes the sensor is working and connected.


----------



## Harold (Dec 23, 2003)

Catmandoo said:


> Correct me if I'm wrong but I thought that a Garmin unit using a wheel sensor will automatically default to the distance being recorded by the sensor and will ignore the GPS data. Thus it won't matter which combo of the 3 GPS systems you set it to.
> 
> This of course, assumes the sensor is working and connected.


This is correct. Which is why I said after it was pointed out that both computers have wheel sensors, that the distance problem is related to the wheel sensor.

But with that said, the wheel sensor does nothing to the spatial data that's recorded by the computer. Your choice of positioning constellation and recording settings will still have an effect on the map.

Another thing occurred to me - exactly where were the differing distances reported? Were they on the device screen, or on a reporting website like Strava or Garmin Connect?

If on the device screen, are ALL settings identical? Aside from recording interval, I'm thinking about the auto pause settings in particular. Auto pause being on will reduce the reported distance on the computer compared to the same device with Auto Pause disabled. For consistency's sake, I prefer to record everything unimpeded and let software sort out stopped time later on.

Also, things like differences in start/stop times or locations, as well as times you get separated and one rider might goof around at an intersection a bit can throw things off.

Also, Strava has been known to throw out sensor data if the GPS has a recording error. This one is kinda hard to track down, honestly. They have a knowledge base article about it somewhere. You can download some software to check your GPS files for errors.


----------



## Sparticus (Dec 28, 1999)

Catmandoo said:


> Correct me if I'm wrong but I thought that a Garmin unit using a wheel sensor will automatically default to the distance being recorded by the sensor and will ignore the GPS data. Thus it won't matter which combo of the 3 GPS systems you set it to.
> 
> This of course, assumes the sensor is working and connected.


Ah, okay. I didn't know this. I assumed (I know, I know) that whenever the Garmin head unit detects a wheel sensor, that it will ignore the sensor and employ data from the satellites until said satellite data becomes interrupted, at which time it will turn to the wheel sensor for "fill-in" data.

But you're saying that's not the case -- that in the presence of a wheel sensor, the head unit ignores all the satellites all the time. Correct?

I better take some rollout measurements and input them.
=sParty


----------



## Harold (Dec 23, 2003)

Sparticus said:


> Ah, okay. I didn't know this. I assumed (I know, I know) that whenever the Garmin head unit detects a wheel sensor, that it will ignore the sensor and employ data from the satellites until said satellite data becomes interrupted, at which time it will turn to the wheel sensor for "fill-in" data.
> 
> But you're saying that's not the case -- that in the presence of a wheel sensor, the head unit ignores all the satellites all the time. Correct?
> 
> ...


It USED to work that way, when Garmin first introduced them. But they fixed that a long time ago. I think that fix appeared as a firmware update to the Edge 500 roundabouts.

The way it works now is that if the wheel sensor is present, data from it will be used regardless of the GPS signal quality.


----------



## Lone Rager (Dec 13, 2013)

From my 705, 500, and onward, the wheel sensor was primary for distance and speed. Auto calibration is decent if it's done over a relatively straight track with good satellite visibility. For a while I used to do several successive auto calibrations going down a long gradual hill from my house, record and average them, then switch to manual calibration and input that average. I've also done careful rollouts, particularly on road bikes. I don't bother anymore.


----------



## Sparticus (Dec 28, 1999)

Lone Rager said:


> From my 705, 500, and onward, the wheel sensor was primary for distance and speed. Auto calibration is decent if it's done over a relatively straight track with good satellite visibility. For a while I used to do several successive auto calibrations going down a long gradual hill from my house, record and average them, then switch to manual calibration and input that average. I've also done careful rollouts, particularly on road bikes. I don't bother anymore.


I'll perform rollout measurements for the 6 bikes in my household outfitted with speed sensors... and it'll be a pain. But given the disparity in Garmin distance measurements from one bike/sensor combination to the next, I don't see an alternative.

It annoys me to have to do it. Why? Because considering the technology at Garmin's disposal in 2020, it'd be easy for them to develop a system that served the user far better. Consider this. The head unit knows at any given time how many satellites it's connected to. It also knows the signal strength of each of those satellites. Garmin could easily write an algorithm whereby each wheel rotation (rotations are a known factor thanks to the speed sensor) is constantly being compared to satellite-measured distance whenever satellite reception exceeds X% (pick a high percentage.) Then, whenever satellite reception is strong, the head unit could/would constantly compare the wheel's rotational distance with reliable satellite-measured distance and use that data comparison to fine tune the wheel's accuracy. The head unit could/would adjust the wheel measurement input down to a tenth (maybe even a hundredth) of a millimeter.

There'd be no need to perform arcane wheel rollout measurements manually. A well thought out system by Garmin wouldn't just measure the wheel once like it does now -- it'd measure constantly, every time high satellite strength warrants. The user could rest assured that his/her Garmin distance accuracy was actually improving with every ride.

There's no reason Garmin couldn't do this. In fact I made the mistake of assuming Garmin already had. This is what annoys me about Garmin. They think about their product more than they think about the people who use it.

Okay, enough whining. Off to measure a few wheels and then manually input data that shouldn't have to be input manually.
=sParty


----------



## Le Duke (Mar 23, 2009)

Sparticus said:


> I'll perform rollout measurements for the 6 bikes in my household outfitted with speed sensors... and it'll be a pain. But given the disparity in Garmin distance measurements from one bike/sensor combination to the next, I don't see an alternative.
> 
> It annoys me to have to do it. Why? Because considering the technology at Garmin's disposal in 2020, it'd be easy for them to develop a system that served the user far better. Consider this. The head unit knows at any given time how many satellites it's connected to. It also knows the signal strength of each of those satellites. Garmin could easily write an algorithm whereby each wheel rotation (rotations are a known factor thanks to the speed sensor) is constantly being compared to satellite-measured distance whenever satellite reception exceeds X% (pick a high percentage.) Then, whenever satellite reception is strong, the head unit could/would constantly compare the wheel's rotational distance with reliable satellite-measured distance and use that data comparison to fine tune the wheel's accuracy. The head unit could/would adjust the wheel measurement input down to a tenth (maybe even a hundredth) of a millimeter.
> 
> ...


The problem with this is that it relies upon a fundamental misunderstanding of GPS and how your receiver achieves a location solution.

What gets you your location on the ground is basically a timestamp in the GPS radio code. When your receiver first starts up, it takes an average of the times being broadcast by four or more birds to achieve a base setting for TIME. Then, your receiver (your Garmin) takes the data from four or more birds, and with that time data from those birds, calculates the distance from each one of them based upon a constant (speed of light), based upon the location of the birds in space (also included in GPS code), and the difference between the time of transmission (TOT) and the time of arrival (the base time discussed above). TOA-TOT * Speed of Light = distance.

The problem with your statement is that you say "satellite measured distance"; the satellites don't measure anything. They don't receive any input at all from your Garmin. It doesn't transmit any data on a frequency that those birds can receive. The only thing doing any kind of calculation or measurement is the Garmin head unit itself, and that is only as good as the inputs. If you have some kind of canyon/urban canyon effect going on, the time that the signal travels will be longer, and the distance from the satellite that the Garmin calculates will be longer, and the point on the ground will be off from the ground truth.


----------



## Harold (Dec 23, 2003)

It's also worth noting that the Garmin receiver very well might update the calibration of the wheel sensor IF conditions are suitable to do so.

It's happened before on mine. It has somewhat randomly beeped at me on a ride and when I looked down at the screen to see what it was doing, I saw a message about the auto calibration having been updated.

The key when using auto calibrate is to run it on a stretch of road that's as long and as straight as you can get, with as open a view to the sky as possible, and to then actually ride it as straight as you can get, changing speed as little as possible.

Changes in speed, swerves, and errors inherent in the calculation process can be masked by the recording rate and fail to be accounted for during the auto calibration process.

If you don't ever encounter that kind of situation, then auto calibrate has a lower likelihood of being very accurate. Relatively small discrepancies during the calibration process will magnify the greater the distance of the ride.


----------



## Catmandoo (Dec 20, 2018)

As a comment about the older generation Garmin speed sensors, that they are vulnerable to errors when on or near a lot of steel, such as the bike path on the Mario Cuomo bridge in NY, as I discovered this morning. The speed was all over the place - 4, 5, 8, 10, etc.... I've seen this before when riding over a different bridge in NYC that has a segment that is steel grating. It's not an issue I worry about, just interesting to see this happen.


----------



## Harold (Dec 23, 2003)

Catmandoo said:


> As a comment about the older generation Garmin speed sensors, that they are vulnerable to errors when on or near a lot of steel, such as the bike path on the Mario Cuomo bridge in NY, as I discovered this morning. The speed was all over the place - 4, 5, 8, 10, etc.... I've seen this before when riding over a different bridge in NYC that has a segment that is steel grating. It's not an issue I worry about, just interesting to see this happen.


Are you talking about the oldest combo ones that used magnets?

Or the ones that determine wheel rotations off of the magnetic field?


----------



## Sparticus (Dec 28, 1999)

Le Duke said:


> The problem with this is that it relies upon a fundamental misunderstanding of GPS and how your receiver achieves a location solution.
> 
> What gets you your location on the ground is basically a timestamp in the GPS radio code. When your receiver first starts up, it takes an average of the times being broadcast by four or more birds to achieve a base setting for TIME. Then, your receiver (your Garmin) takes the data from four or more birds, and with that time data from those birds, calculates the distance from each one of them based upon a constant (speed of light), based upon the location of the birds in space (also included in GPS code), and the difference between the time of transmission (TOT) and the time of arrival (the base time discussed above). TOA-TOT * Speed of Light = distance.
> 
> The problem with your statement is that you say "satellite measured distance"; the satellites don't measure anything. They don't receive any input at all from your Garmin. It doesn't transmit any data on a frequency that those birds can receive. The only thing doing any kind of calculation or measurement is the Garmin head unit itself, and that is only as good as the inputs. If you have some kind of canyon/urban canyon effect going on, the time that the signal travels will be longer, and the distance from the satellite that the Garmin calculates will be longer, and the point on the ground will be off from the ground truth.


I know that satellites don't measure distance to my Garmin head unit; it's the other way 'round. Still, distance is measured from one to the other. That's all I'm saying.

If Garmin can offer an "automatic" setting to compute wheel circumference (and Garmin does), then there exists a way to make that computation far more accurate and easy to employ than it currently is.
=sParty


----------



## Harold (Dec 23, 2003)

Sparticus said:


> If Garmin can offer an "automatic" setting to compute wheel circumference (and Garmin does), then there exists a way to make that computation far more accurate and easy to employ than it currently is.
> =sParty


Not as simply as you think. As I said, there already exists a means whereby the recent ones will update their auto calibration if certain conditions are met.

Lone Rager mentioned taking special effort to calibrate his Garmins in the past. Does anyone else take extra efforts to run the auto calibration under ideal conditions? I don't.

Putting additional processor requirements onto the head unit to constantly analyze the wheel sensor calibration for accuracy is possible, but it's going to do several things. It's going to increase the cost of the hardware, so it can accommodate the processing demands. It's going to increase the demand on the battery, so to get sufficient battery life, the battery will need to be bigger. Which will mean the device will have to be bigger. That becomes quite a cycle once you get into it. A lot of people wouldn't be happy with the increased cost and the increased device size.

It's also going to require a lot of extra work behind the scenes with regards to accuracy. Right now, the consumer grade stuff really is NOT as accurate as you think it is. You have to figure that there is a certain amount of error inherent in every single location the GPS computes. That error compounds over the course of a track. Then you presume to use THAT to compute a highly accurate rollout calculation for your wheel sensor? Really, it might be fine if you want a bit better than GPS-only accuracy. But if you want the best speed/distance accuracy possible, the correct answer will ALWAYS to do the rollout yourself. GPS hardware will never be able to determine the circumference of your wheel better than you can measure yourself with simple measuring devices.


----------



## Catmandoo (Dec 20, 2018)

Harold said:


> Are you talking about the oldest combo ones that used magnets?
> 
> Or the ones that determine wheel rotations off of the magnetic field?


I never knew any of the GPS units used a speed sensor that had a spoke ?, magnet.

My sensors are a Garmin from maybe 3 years ago, so sense earths magnetic field.


----------



## Harold (Dec 23, 2003)

Catmandoo said:


> I never knew any of the GPS units used a speed sensor that had a spoke ?, magnet.
> 
> My sensors are a Garmin from maybe 3 years ago, so sense earths magnetic field.


Yeah. the earliest ones did. was a combo speed/cadence sensor that required a magnet on your spoke AND a magnet on the crank arm. mounted on your chainstay.


----------



## Sparticus (Dec 28, 1999)

Harold said:


> Not as simply as you think. As I said, there already exists a means whereby the recent ones will update their auto calibration if certain conditions are met.
> 
> Lone Rager mentioned taking special effort to calibrate his Garmins in the past. Does anyone else take extra efforts to run the auto calibration under ideal conditions? I don't.
> 
> ...


Harold, I appreciate your patience (as well as that of everyone else contributing to this thread.) I capitulated and performed the rollout measurements for all 6 of my GF's & my wheels without much trouble. Hopefully that'll be it - distance measurements will be more accurate. We'll see.

Or we won't. How can I tell if they're more accurate? I dunno. I suppose the best I can hope for is that our Garmin units will display similar distance readouts at the end of each ride. If they do, that'll be good enough for me. At this point I know little more than this: 1 mile difference in 15 is not close enough.

Thanks again,
=sParty


----------



## Lone Rager (Dec 13, 2013)

I keep a separate wheel and cadence sensor on each of our 6 bikes, so once calibrated, they're good as long as something doesn't change. It helps to name the sensor something recognizable on your Garmins. 

Garmin GSC10 combo magnet based wheel and cadence sensors were around for a long time. Wahoo still makes similar, I believe, and Trek had their magnet based Duo-trap sensors, either configured like a GSC10 or mounted integral and through the NDS chainstay. Other third party magnet based sensors were out there too. These have always been bulletproof if my use on road and mtb, provide the magnets are properly situated with respect to their pickups. I'm still using the original GSC10 I got with my 705 over 10 years ago on one of my bikes. On a couple of occasions I've had issues where water had gotten in, but baking them out in the sun and resetting them restored them to normal operation. Of course I have the newer "magnetless" sensors too. Certainly easier to deal with. 

In my use and understanding, these sensors simply sense a rotation and send that fact to the head unit, which then counts rotations and applies the calibration factor for speed and distance. 

IDK how the newest Garmin Speedsensor 2 recording type works but I assume it counts revolutions with a time stamp and uploads that to the app. IDK where it gets the wheel circumference from or how it is input.

In my experience, the way you think something should work, or what might be a sensible or good way for it to work, does not correlate well with how Garmin actually does it.


----------



## Harold (Dec 23, 2003)

Sparticus said:


> How can I tell if they're more accurate?


Now that's where all this stuff gets really interesting.

I've touched on this before as it relates to elevation measurements (particularly with climbing totals) and it really isn't easy to determine a "baseline" to say that this computer is more accurate than that one. It's not quite as bad for distance as it is for elevation, but it's still a thing.

You see people talk a lot about how such-and-such is more accurate than that-other-thing. How do they know this? They don't, really. Someone, somewhere has made an assumption about the baseline measurement. Often enough, that assumed baseline is not very accurate to begin with. So a measurement that deviates from it more might be viewed as less accurate.

What you CAN assess is repeatability with your own previous measurements and between two bikes riding the same route at the same time. Don't think of it in terms of which one is more "correct" because you simply don't know what the most correct measurement would be in this case. It's possible to make a HIGHLY careful measurement of a trail with a very precisely calibrated tool, but that would be VERY SLOW and tedious work. Think of things in terms of consistency.

If you want all the wheelsets for all your bikes to have consistent measurements, then careful calibration should get you closer to that point. You can be pretty careful about your calibration, but there's always going to be a certain amount of uncontrollable variation that you simply can't account for. Airtime will mess with measurements taken from a wheel sensor. Variations in tire pressure due to elevation change could affect your calibration enough to make a difference. Say you calibrated at x,y pressures, but then you go do a ride where your high point is a solid 5,000ft higher than your low point at the trailhead. Your tire pressure will be notably different at the two elevations, and it'll mess with the distance calculations from your wheel sensor. A lot of people never really deal with this from the perspective of computer calibration, but it's well documented that tire pressures affect calibration. Folks who ride big mountains might adjust tire pressures throughout a ride because of traction/handling issues caused by the changing air pressures at different elevations, for sure. Or say when I rode my fatbike in deep snow vs. frozen dirt. I ran MUCH higher pressures on frozen dirt than on deep snow, and that certainly affected the wheel sensor calibration. But I didn't recalibrate every time conditions changed.

Garmin's current auto calibration satisfies me in that it does better than GPS-only. It does make adjustments to calibration if there are large discrepancies. I could get tighter, more consistent results with other methods, but I'm just not willing to put in the extra effort. I don't care THAT much.


----------



## Sparticus (Dec 28, 1999)

Harold said:


> I don't care THAT much.


Me neither. I just want to believe that my distance tracking device is doing its job as accurately as possible.

Belief - that's what I'm in pursuit of. Belief trumps reality.

Sorry about using that word. Until 2020, it meant to eclipse or upstage. Going forward it may soon come to mean the opposite. Methinks the lexicon is in need of a replacement.
=sParty


----------



## SOC (Sep 12, 2010)

Sparticus said:


> Thanks, LR. I should have mentioned that in the case above, both bikes were outfitted with speed sensors and set to 1/sec data recording.
> 
> For the heck of it I'm going to try GPS + Galileo to see if the two units yield more similar distance measurements. If they don't, I'll consider resetting to GPS + GLONASS.
> 
> ...


Reviving an OLD thread here. I know it largely evolved into a wheel speed sensor discussion, but @Sparticus -did you ever compare the performance of the GPS + Galileo vs the GPS + GLONASS?
Did you see any tangible differences?
Do you have a preference for your riding location?
Thanks!!


----------



## Sparticus (Dec 28, 1999)

SOC said:


> Reviving an OLD thread here. I know it largely evolved into a wheel speed sensor discussion, but @Sparticus -did you ever compare the performance of the GPS + Galileo vs the GPS + GLONASS?
> Did you see any tangible differences?
> Do you have a preference for your riding location?
> Thanks!!


Hate to admit it but ... I forget. 
=sParty


----------



## SOC (Sep 12, 2010)

Sparticus said:


> Hate to admit it but ... I forget.
> =sParty


LOL. No worries!
I ride similar terrain as you, so was just curious.
Happy trails!


----------



## Jayem (Jul 16, 2005)

There are a LOT more sats than the initial GPS constellation, so lack of sats is typically not anywhere near as big as it used to be. The more, the better though. It was said that we might do better to have glonass at higher latitudes, but at higher latitudes we actually see more GPS satellites and for longer, due to line of sight and them not being masked by the earth as much. The system was originally intended to fling ICBMs over the poles, so we actually have better availability up higher in latitude due to that line of sight. The most definitive factor may be signal strength, thats the biggest drawback/folly of GPS, the signal is so relatively weak. Id choose glonass vs Galileo based on watts/frequency.


----------



## SOC (Sep 12, 2010)

Jayem said:


> There are a LOT more sats than the initial GPS constellation, so lack of sats is typically not anywhere near as big as it used to be. The more, the better though. It was said that we might do better to have glonass at higher latitudes, but at higher latitudes we actually see more GPS satellites and for longer, due to line of sight and them not being masked by the earth as much. The system was originally intended to fling ICBMs over the poles, so we actually have better availability up higher in latitude due to that line of sight. The most definitive factor may be signal strength, thats the biggest drawback/folly of GPS, the signal is so relatively weak. Id choose glonass vs Galileo based on watts/frequency.


Great feedback Jayem.
I'm right at the 45th parallel; so not too high and not too low. 

I think I'm going to leave things at GPS + CLONASS for now. Thanks again for the input.


----------

