As you run, MapRun calculates the distance from where the GPS says you are to the Lat/Lng of each control. If the distance is less than the punching tolerance, then MapRun will punch the control ... subject to the punching logic eg no punching of controls before Start is punched etc.
The main reasons for setting a punching tolerance default of 15m is:
- There will be inaccuracy with the Lat/Lng of controls. Even for controls placed using Google Earth imagery, the Lat/Lng can be in error by several metres.
- There will be a difference between where you are standing and what the GPS reports as your location. See further info on this on the www.maprunners.com.au website. It is common for phone GPS's to be in error by 5-7 metres.
15m is generally a good balance between - missed punches where the runner is at the exact location but the distance calculated (as described above) is greater than the punching tolerance, and being too loose so that there is wide variability in where punches occur for different runners.
A 20-30m tolerance can be required in heavily forested areas to achieve this balance.