I've got a fitbit alta but I'm not too happy with its performance. I think it's tracking less distance than I'm running. The tracker said I'd run 5.5k this morning, but the app said it was 6.5k.
Anyone else with this discrepancy?
Also, anyone got recommendations for good, accurate trackers?
The Alta is like the fitbit flex, I believe, and only counts steps. It then converts this into distance traveled by multiplying by your average step length, so will only ever be an estimate of distance at best. If your Alta is consistently under-recording you can adjust the stride length from the website dashboard (look under settings - the gearwheel top right). On the flex I can set a walking stride and a running stride, but that's it.
If you want to accurately track your distance traveled the best thing to do is use a gps running watch (e.g. one of the Garmin Forerunner series - other makes are available). I find that my Garmin is more consistently accurate than using my phone gps plusan app (and it doesn't flatten the phone battery). You are using a piece of hardware that is dedicated to doing one thing well, rather than a phone which is trying to do everything. However, a GPS watch doesn't do everything (e.g. it doesn't count steps) and is not a direct replacement for an activity tracker such as the Alta which is designed to be worn all day.
I use a Fitbit Flex to track my activity, a Garmin Forerunner 610 to track my runs and a Garmin Edge 25 to track my cycling. I use the two Garmins in association with a Mio wrist heart rate monitor. The flex stays on my wrist all the time. The two Garmins and Mio only come out when I'm undertaking an appropriate activity.
Do you need a GPS watch? That depends on you. How important is it for you to track what you are doing? Is analysing the data after every run important? On the minus side - a GPS watch is relatively expensive. On the plus side, the more you get in to running, the more useful they become. I came back from a half marathon yesterday and downloaded my GPS trace straight away. I then spent the evening looking at my data and deciding where I'd gone wrong. The other big advantage of having a watch is that, now you've gone out and bought it, you have to keep going for runs regularly to justify having one. They are a great motivator 
I was going to go for the fitbit but number one son persuaded me to go for the garmin. He said the fitbit wouldn't be accurate as distance is based on number of steps and everyone's stride is different, so I went for a garmin forerunner 10. Got it very cheaply second hand and I love it! It monitors distance, time speed, calories etc. I can set it for laps or as a virtual pacer and best of all it shows me the exact route online when I'm finished, so I can see exactly what speed/pace I was doing at various stages of the run. It also tells me every time I hit a personal best in distance or time. Love it to pieces - oh and it's pretty too and tells the time 😆
I use Map My Walk app - very reliable & free
I have a fit bit charge HR and I love it for counting the steps but it is next to useless for the distance. It can only estimate by the amount of steps you take. Map my walk is the best way to get an accurate distance or if you dont want to take a phone with you then when you get home you can plot your exact walk on plot my route. plotaroute.com/routeplanner
Garmin forerunner 10 - love it.
Thanks for all your input and comments.
I've had a good look through all the info I can find about the fitbit alta and it seems that I should have input my walking and running stride lengths into my account when I first got it. Which I didn't, so it was using average stride lengths for someone my height and weight. So I've added my own proper lengths, and will see if that makes any difference to the indiscrepancies such as one clocked 5k time of 24 minutes followed a few days later by one of 33 minutes...
And, if that doesn't work, I'll probably have to quietly purchase a garmin.
I have a tomtom cardio 2 which I love! Think garmin are generally considered to be the best gps running watches and you can pick the basic versions up from ebay for decent prices.
You can use the fit bit ap on your phone to map your run via gps.
That sounds like a great idea. I'll give it a go.
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