GPS vs. GPS+GLONASS

First, the GPS is only active during an Activity Application where GPS tracking of location would be useful. So, it's ON during a Run or Cycling App but OFF during an Indoor Run or Indoor Cycling App. It's also OFF when you are using the watch simply as a smart watch and the Activity Tracking feature in this basic operating mode only uses the internal gyro's for step counts and the heart monitor to track the heart rate if that is enabled.

As for GPS + GLONASS, there is a slight increase in battery draw with both enabled but the speed of acquiring a position lock with both modes operating really has to be seen to be believed. I started with the Forerunner 15 which is GPS only and it was typical to have to wait anywhere between 3 and 15 minutes to get a position lock and the length of time was dependent on the last known position, how cloudy the sky cover was, and the positioning of the satellites in the sky. With both modes enabled on my 235 I usually have a position lock before I get the key in my back door to lock it and the longest I have had to wait I would guess at being between 30 and 45 seconds.

As for the effect of the increased draw on battery life between charges it might be significant to an Ultra Marathon runner on a 50 mile or more run but I could be wrong about that. May also matter to an Ironman competitor. For more normal folks I don't think it really matters. According to Garmin the battery life with all the tracking features, using the wrist based heart monitor and with a smart phone linked up using GPS+GLONASS for the full period the total life is 9 hours. If you switch to GPS only you can get that battery life up to 11 hours.

Because Lithium Ion batteries should be discharged to under 40% at least once a month I decided to forego charging my 235 this weekend. So the last charge was Friday morning at about 6:00 AM. Since that time I've put in 1.5 hours of outdoor runs using GPS + GLONASS plus another 4 hours of indoor runs where the heart rate was tracked using a chest monitor. Also had my smart phone paired up for the full time span and after about 54 hours total time the battery on my 235 was only down to 38%. For me I don't think the extra battery drain using GPS + GLONASS will ever be a problem because if I'm not trying to run the battery down for life cycle reasons I tend to link it up and charge it on a daily basis.

Hello.Same problem with accuracy. I make screenshot from tomtom spark 3 and forerunner 235 ,the diference is huge, I make this route with both watchs on a hand. Any ideas how to improve accuracy ? no diference with glonas or without. Alsi in distance is diference.ciq.forums.garmin.com/.../1393938.jpg

Since update 7.70 the GPS from the 235 acts very weird / unpredictable. I complained to gamrin about it and they said they were aware of the issue. We're months later and still nu update (7.80 didn't fix GPS).

I switched from smart data recordning to every second,and now I think its good.

I switched from smart data recordning to every second,and now I think its good.

Where's that option located?

Found it! I've switched to Every Second, let's see if it works.

https://www8.garmin.com/manuals/webh...B5453F7EB.html

[h=1]Data Recording Settings[/h] Select > Menu > Settings > System > Data Recording.

Smart
Records key points where you change direction, pace, or heart rate. Your activity record is smaller, allowing you to store more activities on the device memory.

Every Second
Records points every second. It creates a very detailed record of your activity and increases the size of the activity record.