All the Maprun things I've done I print a paper map and run with that (like proper orienteering) and have my phone set to maximum volume and secreted somewhere about my person. Do you navigate using the phone screen?
No, I print out the map too, but from an Australian site, so...
Well, OK, I'm just rubbish :(
My GPS does give some ridiculous data about where I've been, and its only stopped 1/4 times at the finish without randomly wandering around: seems that others don't have that problem and I'm not sure why.
Different GPS devices clearly do different things in terms of accuracy and frequency of logging. I occasionally run with both phone and Garmin logging position and the traces can be 10+m apart even in moorland. The Garmin also logs less frequently so changes of direction can be bad too.
MapRunG works very well for me.
If you're using a Garmin, make sure to set it to 1-second recording rather than "smart" recording, the latter only records a point when you change direction or altitude, I believe.
If it records every time I fall over it'll be fine for forest races...
Except, its not the case since I dont have a Garmin.