GNSS time to output

Why does my system take such a long time to get a position solution?

The system may be having to undergo a "COLD_START" which refers to the system needing to download the GPS Almanac ( which consists of coarse orbit and status information for each satellite in the constellation, an Ionospheric model, and information to relate GPS derived time to Coordinated Universal Time (UTC) and Ephemeris data (which consists of precise satellite orbit data). The Almanac can take anywhere from a minute to hour, depending on the receiver type and the visibility conditions.

Normally the system will save these parameters in its memory once it has downloaded them the first time, and then will operate from a WARM_START (if it has the almanac already) and a HOT_START (if it has the almanac and the ephemeris).

The system would have to download a new almanac for three reasons:

• Almanac data can be used for months after a download, but if the receiver has not been turned on in the past 180 days it is usually deemed invalid
• If the internal memory was failing to save it for some reason

Also, if the unit had travelled across the globe to a new location, then it also may take a little longer to get a lock as the last known position cannot be used to speed up the time to first fix. On the latest versions of our units, the specs are listed as:

Cold start <50s typical (with no almanac, ephemerides and no approximate time or position)

Hot start <35s typical (with almanac & ephemerides saved, approximate time and position entered.)

Ultimately if your card is taking more than the times mentioned here to get a position lock, and it is happening every time you power the unit up, then it would suggest the internal memory has a fault. We can perform a factory reset on the card and reapply the settings if this is the case, to hopefully restore it to normal functionality in the field. Contact us at support@oxts.com for further help.