To view the GPS satellites being used and their signal to noise ratio in Mercury Venus Transit Maestro you have to open the GPS Satellite window. Some units, such as the GPSMap 76, may not be able to report the satellite contellation used to provide the position and time.

1. Choose Setup > GPS Satellite Window…
    

When a GPS unit is connected to the Mac, you can transfer the coordinates and altitude given by the device. All Garmin USB GPS units using the proprietary Garmin PVT protocol (untested with serial devices using a serial to USB converter) are supported and provide real-time positioning. Receivers that only operate in Mass Storage mode while connected can not provide real-time positioning (please refer to Garmin Spanner mode); nevertheless the last position, while the receiver was not connected, is stored inside the unit and can be read.
Recommended models are (Mass Storage mode must be deactivated and interface set to GARMIN with older units and Garmin Spanner with newer ones):

• GPS 18x series (puck-like receiver, the most reliable and least expensive)
• eTrex series (old units such as the Legend H, Legend HCx, Summit Cx, Venture Cx or Vista HCx)
• GPSMap 60CSx, GPSMap 60CS or GPSMap 60
• GPSMap 62stc, GPSMap 62st, GPSMap 62sc, GPSMap 62s or GPSMap 62 (firmware older than 3.40)
• GPSMap 64st, GPSMap 64s or GPSMap 64
• GPSMap 76CSx, GPSMap 76CS or GPSMap 76C
• GPSMap 78s, GPSMap 78sc or GPSMap 78 (firmware older than 3.40)
• Oregon series
• Montana series
• Rino 6xx series

All serial GPS receivers conforming to the NMEA 0183 standard should also be supported. To configure those devices connect them first either with a Serial to USB adapter or by Bluetooth.
Recommended models are:

• DUAL XGPS160 SkyPro (Bluetooth operating at 10Hz, so up to ten positions per second); there is also a battery level indicator on the satellite constellation display
• Garmin GLO (Bluetooth operating at 5Hz, so up to five positions per second)
• Garmin 18x LVC or PC
• Qstarz BT-Q818X (Bluetooth operating at 5Hz, so up to five positions per second)
• G-Mouse/DIYmall VK-162 (cheap USB unit, about USD15 or 15€)

For more information see Setting the observer’s location.

With Mercury Venus Transit Maestro Pro and an appropriate GPS unit, the Mac can use the Pulse-Per-Second signal to determine the clock error adjustment.

For receivers that only operate in Mass Storage mode while connected, only the last position, while the receiver was not connected, is to be read. Models usually are:

• eTrex series (newer units such as 10, 20 and 30)
• Nüvi series
• Zūmo series
• Dēzl series
• Camper series

The recommended settings for tracks can be found below.

1. Recording waypoints every second is usually not necessary.