Use GpsGate with Garmin GPS 18 (USB)
The USB version of the Garmin GPS 18 does not support NMEA, it only supports Garmin's own protocol. Therefore very few GPS applications can use the Garmin GPS 18.

GpsGate solves this problem!

You can connect GpsGate to the Garmin GPS 18, and most other Garmin USB GPS receivers as well. GpsGate will make the Garmin GPS appear as a normal NMEA GPS connected to a serial port. With GpsGate Standard you can connect any number of GPS applications to the GPS at the same time (2 applications with GpsGate Express!

Steps to connect to a Garmin GPS 18:
1. Open the settings menu.
2. Select "Garmin USB" as Input.
3. In the Output dropdown, select "Virtual ports".
4. Select a port and click "Add virtual port" (e.g. COM4)
5. Repeat step 4. to create as many virtual ports as you need (one per application using the GPS at the same time).
6. Close the settings menu and you are finished!