Ashvin is more like a SAM, whereas PINAKA is more like a BM.its part of anti ballitic missile program.. its endoatmoshpheric .. unlike prithvu which is exoatmoshpheric.
my question was..if we have ashwin why do we need pinaka guided version..
The main difference is in between thrust produced by both. PINAKA is just a guided rocket system with comparatively less thrust whereas Ashvin does produce a lot more thrust. The thrust produced by PINAKA is like a 100m sprinter, whereas Ashvin is like a 400m sprinter.
Then comes the guidance system. PINAKA is guided by either LASER or by GPS/IRNSS, whereas Ashvin does make use of RADAR based guidance mode. You simply can't replace one with another.