The only difference between the internal antenna and external antenna is installed ways. Internal antenna is built into the device. External antenna may be installed at a remote location.

Gps internal antenna can accept the signal through the windshield but not through thick and hard thing to accept signals


Some devices built built-in high sensitivity GPS antenna. These devices may be able to pick up the position of the GPS signal

The best way to determine whether the need for an external antenna, you can install the device on which the location and power supplies. Allow plenty of time to get the device GPS signals. If it can receive a signal at that location, no external antenna. If the device can not get a GPS signal, for so long the need for external antennas

External GPS Antenna

Internal GPS Antenna