Sygic India is an application specially dedicated to the road maps of India and let me tell you that it is really expensive usually (1599 INR). Most of the times I have users discussing on the forum to download the apk file for free of this application from other sources but the actual point it is that why is this navigation application is used by most of the users on smartphones even when they have Google Maps to do the same.
Sygic GPS and Navigation application try to take countries separately into their account and then create an application specifically for them. So, the amount of data related to roads, shops, small congested areas and other ways of transportation which are not mentioned in Google Maps will be available here (in short the information is highly detailed) but the UI is not that good and it is a bit laggy.
Because of that detailed information available in this application, the price is so high. The updated related to the construction of the road or blockage of any major road will be quickly updated in this application which is again not possible in the case of Google Maps.
Once you install this application you will have to choose few particular states which will be available on your phone. This application does not require any internet connection to operate because one you choose the state, all the maps related to that area will be downloaded and you will just have to turn ON the GPS location services on your phone and that will be all for this application to work.
Similarly at another point of time you can download the maps of some other states, this application is not free for iOS users and it is really expensive on App Store too (1599 INR). Please let us know about any problem which you face while using this application.