Fitbit Surge inaccurate pace mile 3, which compensates mile 4

[marathon_dreams]

I've been running with the Surge for 3 months now and for the most part I'm finding it to be decent.  In comparison to using my Strava app on my phone it does appear to jip mileage and my pace is often recorded slower.  Most recently I'm noticing that always in mile 3 it will record a higher or lower pace than what my watch has been saying (for instance...avg pace for the entire mile is roughly 8:29 and then it will record at 8:08) and then mile 4 will compensate (again...avg pace for entire 4th mile was just under 8:30 and then recorded at 8:50). I often run competitively against myself and wanted a GPS watch solely to avoid carrying my phone so these innacuracies become annoying.

I've read many times that FitBit relies on my stride to calculate, which makes NO sense to me at all.  If it's GPS capable it should track me from mile A to mile B to mile C and so on based on the time it took me to reach that point as well as an accurate measure of location.

Any suggestions or help?

P.S.  I have recorded my stride length, which did help with better accuracy of mileage but still off.  

[shipo]

@marathon_dreams, I'm assuming your running in "Free Run" mode using GPS; yes, no?  If "yes" then your stride length setting in your profile is irrelevant as it is ignored when in GPS mode.

Have you looked at the map plot of your runs?  If so, does the mile 3 mark look to be in the correct spot?  I ask because if the "error" your seeing is pretty consistent, then it is possible or even likely you're simply running a bit slower on mile 3 either because that's your body's natural rhythm or because that mile is slightly up hill.

FWIW, I've been running with a Surge for almost a year and a half now and have never seen a mile over mile compensation like you describe.

[marathon_dreams]

Yes, I'm running in Free Mode so good to know it tracks only as GPS, though
I find it interesting that it became more accurate once I entered my stride
length correctly. I run different areas so terrain is often not the same.
It's possible I run slower in mile three, but I would hope (and want) the
watch's avg pace would reflect that accurately. I will often use "Map My
Run" and this particular 4 mile run was accurate to total distance, but in
the past it could be up to .5 miles off for a 7 mile run.

Also, this just came to mind, I've also had it where I will pause the run
(for traffic or to take a breath) and it seems to not want to catch up and
throws my pace/mileage off.

--
Kori Podjan

[shipo]

Yeah, terrain, hills, uneven roads, cross streets, traffic, parked cars, other pedestrians, and any number of other dynamics will mess with your per mile pace.  My typical lunch time run sees a lot of variance due to a sketchy running surface for at least a quarter of the run plus about 1,200 feet of climbing with decents steep enough to cause me to slow the pace way down to keep from hurting myself.  Here is a fairly typical set of splits for the above mentioned lunch time run:

• Mile 01: 10:17
• Mile 02: 09:30
• Mile 03: 08:59
• Mile 04: 08:34
• Mile 05: 09:18
• Mile 06: 08:54
• Mile 07: 08:05
• Mile 08: 07:54
• Mile 09: 08:00
• Mile 10: 08:03

Average pace: 8:44

When I look at the current average pace on my Surge during my run it almost never matches the pace for the full mile due to how much my speed varies.