Somnathpur is located about 35km east of Mysore City. You can take two diffreent routes to get to Somnathpur from Mysore. The first is via Bannur and the second is via T.Narsipur, the later is a few km longer.
There are also a road to reach Mandya (32km) and Srirangapatna (32km) from Somnathpur.
Mysore to Ooty via Gudallur distance is about 183km : Mysore City — 24km –> Nanjangud — 43km –> Gundlupet –20km –> Bandipur National Park — 5km –> Karnataka Tamilnadu border — 7km –> Theppakkadu — 17km –> Gudallur Town — 46km –> Pykara Lake — 21km –> Ooty