No you don’t. Whether you are using a PRO + (with built-in GPS), a PRO or a 3.0, you can use functions that use GPS such as bathymetric mapping in boat mode and GPS ice hole marking without a phone or internet connection. In the case of the PRO +, it’s built-in GPS functions independently of your phone and connects directly to satellites. The PRO and 3.0 use your phone’s GPS for these functions, but this works even if you don’t have a phone or internet signal. In this situation, the connection to GPS may be a bit slower than if you have a phone signal, but it still works fine.