Anyone find the GPS on mapmyrun inaccurate?

Someone told me you need to turn off wireless. That your phone picks up singles and it throws it off.

Hey I'll try that because I use Endomondo and it's been so wrong lately and making me cranky about it. Thanks.

All the apps use the GPS hardware built into the phone. Some phones have really poor GPS implementation. Samsung phones tend to be notoriously bad. Samsung also has some of the most popular phones...so a LOT of poor phone GPS in the world. This may lead to some people having better results than others. Different model phones. The same "model" is often actually different from carrier to carrier. A Verizon Galaxy S3 is different than an AT&T Galaxy S3. A buddy with a Verizon Galaxy S3 showed my how he tightened some screws and temporarily got better reception. There is even a phone to phone variation within the same brand and model.

The wifi thing is also interesting. Google and other companies literally drive around taking pictures for street view. They also collect information on what wifi they detect and where the car is when it's detected. They can actually build a map of wifi locations, including protected wifi. If your phone can detect a particular wifi AP, it can tell where you are within the max range of that wifi AP. It's really good for getting a fast approximate lock of where you are. Wifi radius is pretty wide. Again, some phone have implemented poor algorithms for mixing GPS data and wifi location data. I've seen cases with an older Galaxy-S where you can walk along, when you get in range of a wifi AP, your little icon on the screen pulls away from the sidewalk towards the house with that wifi.

Some apps may be better than others because they do more data smoothing and interpolation. You're trying to use a GPS with 30ft accuracy to measure something very precise over time. The better the software is at throwing away outlying data, the better it will be.

Yeah I could never get used to Map My Run, I use Runkeeper on my Galaxy note and it works fine.

The two times I have had issues is between my boyfriend and I and when my phone crashes.
My boyfriend and I will do the same exact distance, but his will measure longer than mine. It is frustrating,
And when my phone crashes and restarts (because I have a TERRIBLE phone) it'll often be inaccurate in it's timing to my distance.

Is RunKeeper really worth it or is it pretty much the same?

I've used the Nike+ Running app and it seems to match what my Garmin GPS watch says, if that helps.

Yesterday I did a walk I midtown manhattan which is all straight lines, and map my run had a distance one mile over google maps. Yet an earlier measurement was right on the money.