GLONASS ruins accuracy

I'd wondered the same thing. I used mine a couple of times with GPS + GLONASS and the resulting tracks were not as accurate as I would have liked. They were just as bad as the tracks from my Polar RCX5 with G5 GPS device. I might try tomorrow with GPS only to see what the difference is. I'm only using mine for walking, so I don't know if my lower speed impacts on accuracy, but I wouldn't imagine it would be that great.

I use GPS + GLONASS on my Edge 520 and get good results, so I was expecting similar from my new 230.

Ah reasonably familiar territory to me on the canal past Sheerwater athletics track.
That is rather poor I agree. However on the basis of just one run hard to make too many conclusions.

Not been up there for a while but I see you seemed to have turned round under a bridge and imagine there is a fair amount of tree cover this time of year. All things that may result in a reduction of the number of satellites locked onto - although GLONASS mode is of course designed to give you more to lock onto.

The general consensus is that GLONASS can help in certain situations (all it really does is give you more satellites to lock onto rather than improve accuracy per se) but may sometimes not help.

AFAIK it's never been documented how GLONASS mode actually works - i.e. do GPS and GLONASS sats get equal priority in being used etc etc

I would suggest giving it a few more goes but if you don't like the results revert back to GPS only.

> I use GPS + GLONASS on my Edge 520 and get good results, so I was expecting similar from my new 230.

Things will generally always be "better" on the bike for GPS accuracy as the device is in a fixed location pointing always straight up at the sky. You also tend to cycle in more "optimum" conditions like on roads etc etc.

The speed may also be an advantage compared to walking - especially if you walk under trees etc etc

I was just re-reading the DC Rainmaker review and anecdotal evidence suggests enabling GLONASS on the 230/235 doesn't do anything much for accuracy, it just uses battery quicker.

Yeah probably. Depends what you mean by accuracy as well. If say your tracks are pretty good but a few metres off the road, GLONASS won't make them more accurate and so be on the road. It's still the same technology after all. If however you run under dense tree cover then GLONASS can help as there is more chance of locking on to enough satellites to give a reasonable track in such circumstances.

Yeah probably. Depends what you mean by accuracy as well. If say your tracks are pretty good but a few metres off the road, GLONASS won't make them more accurate and so be on the road. It's still the same technology after all. If however you run under dense tree cover then GLONASS can help as there is more chance of locking on to enough satellites to give a reasonable track in such circumstances.

I was on a route I've used many times and there's no real tree cover. The track showed I was in the middle of a road when I was actually on the footpath and the track was a bit all over the place.

I'll try again tomorrow and see what the results are.

dei hardt

Here are a couple of activities for comparison.

Here is a walk I did last weekend with GPS and GLONASS enabled for tracking:

https://www.strava.com/activities/658030002

And here is one from today covering the same route using only GPS:

https://www.strava.com/activities/666016814

And here's one recorded with my Polar RCX5 for comparison:

https://www.strava.com/activities/643474449

In all activities I was walking on the footpath on the left side of the road. I made no changes to my arm action. I was following exactly the same route. To me, today's activity looks better and I was getting the autolap markers a little bit earlier. It came up 30m shorter than with GPS and GLONASS. The RCX5 was measuring long by about 5%. It's GPS track looks as bad some phones.

I did a quick test standing in my driveway last night. I let the timer run for 30seconds each time. First time I had GPS, second time I had GPS + GLONASS. I had the watch face facing straight up both times.

When I compared the two tracks, even though I was stationary, the GPS + GLONASS track showed very little movement. The GPS track showed a bit more. I believe the term is called spidering. This aligns with what I've seen on my Edge 520 which is on an out front mount and so has the best reception possible.

It could be that the results I obtained so far were because my arms were naturally hanging down by my side when I walk and may not have given the watch the best GPS reception. Looking at a teardown video of the 630 (which is a similar design to he 230), the location of the GPS receiver is near the top of the display and probably needs your wrist to be up between your waist and your chest for best reception. I may need to bring my arms up for better reception.

My G5 with my RCX5 was in a band on my upper arm so it didn't suffer from any such reception problems.

I think to answer this question you have to know much about how watch uses satellites (how many of them it picks) and how satellites are located (I really don't know of they tried to reach same accuracy on all territories or not).
I think watch's algorithms is very important, including of they use glonass for backup only or combine two locations or take N satellites from both locations. If they have same rounding on these cases.

What I know is
- generally glonass has worse accuracy (both good and glonass are improving but since glonass project started long after GPS it is likely to be behind on this terms)
- systems are not identical. GPS codes the signal with amplitude, glonass with frequency. That gives glonass theoretical advantage when in rain or between trees. Not sure if it helps in reality
- you cannot compare 2 runs directly. Weather affects it, exact location of satellites affects it.. You need more to compare.

I tried GPS only once- saw no increase or decrease of accuracy. Switched back after one run. Normally use GPS+ glonass.
Will try though using it for a month, just to compare.

Tried GPS only mode for couple of runs.
Not sure about accuracy but it looks that it locks to satellites way faster (looks as if it waited for glonass SATs to be found previously)