You might be able to use an external Bluetooth GPS device, like this
Garmin GLO unit, but I don't have one to test with my Pixel C.
As Jerry alluded to, Android supports several location providers (WiFi, cellular, GPS, Bluetooth, etc.), but is ultimately limited by the device's hardware. Android also supports "mock" providers for injecting location data from other sources, such as external GPS devices like the Garmin one I linked, or when developing and testing apps. Some apps treat these mock providers differently than others, so you may run into issues using a Bluetooth GPS device depending on which specific apps you're looking to use it with.