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NMEATime2 - More Information

Tray Bar

Please note to access NMEATime control panel, simply right click on the tray bar icon and select show panel

GPS Receiver Notes

The following are GPS receivers have been tested and the notes at accompany them. If you find that another receiver is working well, please let us know and we can list it here.

  • Generic USB GPS from Amazon (link) - This USB receiver seems to work well. No issues. This GPS is based on the u-blox 6 GPS chip-set and the performance is very good. Please note, when using this GPS receiver with Windows 10, it will set itself up as a GPS Sensor and not a GPS virtual serial port. When in this mode, the OS will control the GPS and applications that expect NMEA information are blocked. This can be changed by uninstalling the GPS sensor driver from windows using the device manager. You can then download a driver that can be acquired from u-blox (ubloxGnss vcpDeviceDriver windows) that supports the virtual serial port.
  • Another GPS from Amazon (u-blox) (link) - This USB receiver seems to work well. No issues. This GPS is based on the u-blox 7 GPS chip-set. See Generic USB GPS from Amazon above for more informaion.
  • BU-353-S4 - USGlobalsat - This USB SiRF Star IV based receiver seems to work well and has no issues.
  • Navibe GM 720 - USB SiRF Star III based GPS works with no issues
  • Holux M-215+ - This USB receiver will function, however it causes Windows 10 to BSOD when connecting/disconnecting the USB physically from the computer. Not recommended.

GPS Performance

The above plot is showing the GPS receiver under a startup condition, cold start. Consumer GPS receivers will not indicate cold start, however it will still navigate and produce time when tracking satellites. The problem is when in this mode, the GPS may not have a full almanac (all the data from the satellites) and the time may be referenced to GPS time (GPS time is different than UTC time) or something close. When the timing portion of the almanac is received, you may notice a jump in timing as depicted above. This jump usually happens within 13 minutes from the time the GPS starts tracking satellites with the antenna in a clear view of the sky. This is the approximate time it takes to download an almanac from the satellites. The plot shows the GPS jumping two seconds taking just a less than five minutes to occur from the start of tracking satellites.

It’s recommended to wait for at least 15 minutes before using the PC for any critical timing application when first powering up the GPS.

The test setup was using a GlobalSat BU-353-S4 USB GPS with the PC referenced to a NTP server. The data was taken using NMEATime2 with the control loop turned off and the control loop logging enabled. You can perform the same test with your GPS receiver. The control loop log will produce a comma separated value file (CSV) where you can perform analysis. The value to use is the Raw Time Difference.

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