What is GPS Aiding Data?

Our latest range of Cellular 2G and LTE-M/NB-IoT devices make use of GPS Aiding data, to dramatically improve the performance of their GPS - speeding up fix times, and increasing battery life.


So what is GPS Aiding Data?

Our current line-up of devices (as of Oct 2020) make use of uBlox GPS modules, and use uBlox's version - AssistNow. Every 5-7 days, the devices download aiding data over the cellular network - from uBlox's servers. This data contains key information: ephemiris, almanac, accurate time and satellite status. In layman's terms this basically means the device gets key information about where the satellites are in the sky, their paths, and other key information. This data is around 50kB worth, and is quick and easy to download. 

Without the aiding data downloads, the GPS module would have to download all of this directly from the satellite when it gets a fix. If it's in poor GPS signal, this could take a long time! Or fail entirely. With aiding data, the device has all this on hand, so when it tries to get a fix, it only needs to get some signal (even weak signal) from a few satellites, and can still compute a position within seconds!


Benefits

  • GPS fix times are significantly reduced. Generally in good signal, we can get a fix in around 10 seconds with the aiding data, without, it takes upwards of 30s. 
  • The fast fixes mean better GPS performance for our hard-wired trackers - for live location tracking
  • For our battery powered trackers, the impact on battery life is significant. Running the GPS takes energy, the less time we can run it for, the less power it will use - increasing battery life!
  • Fixes can be acquired in poor signal conditions - thanks to the Low Noise Amplifiers also fitted to our devices, they will get fixes where other devices simply give up!

Drawbacks

The sole drawback is the tiny 50kB of data use. This is generally not a problem in most applications. But when trying to keep data usage to the absolute minimum - i.e. for NB-IoT - this can eat up the tiny data allowances (100kB for the whole month isn't uncommon). See - NB-IoT data usage on the Yabby GPS and Wi-Fi. However we feel the trade-off is well worth it for the improvements in performance and battery life - and we are looking into other ways to get the data usage down on our upcoming devices. 


Aiding Data Download Errors

If the aiding data download is failing - this error will be seen in the device logs (View Device Logs).

Debug[GSM][Sevr]: HTTP fail online-live1.services.u-blox.com:80 0/4

This means the download has failed, which could be for a few reasons:

  • Temporary network issue - so the device just failed halfway through getting the data. If it's only a couple of logs, it generally isn't much to worry about.
  • Issues with DNS on some NB-IoT networks, see DNS Troubleshooting on 4G
  • Your SIM provider has a lot of firewalls up, and aren't allowing traffic from this server. The uBlox servers should be white listed - see: OEM - What IP addresses should I allow through my firewall?
  • Some other issue (something has changed at uBlox or a FW bug in our devices) - contact DM

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