Using digimesh to synchronize nodes

Hello developers,

currently I try to synchronize a mesh consisting of xBee-Series2 Zigbee 
modules and modified arduino minis. I stuck at the time-synchronization 
because Zigbee doesn't provide any algorithm by default.

Now I was thinking about using Series1 modules and DigiMesh. Does 
anybody now how accuratly the modules are synchronized when synchronized 
sleep mode is enabled.

I know this all depends on how often the nodes wake up. So lets say I 
want to wake up the nodes every 28 seconds. How long is the minimum 
wake-time then?

Does somebody now a good solution to synchronize around 10 nodes in a 
Outdoor Range of 200 meter to a accuracy of 1-10ms?

Thanks everybody in advance!