Almanac Fleet
Almanac Fleet sends a fresh satellite almanac to your GNSS trackers over the air.
A GNSS almanac is the list of which satellites are where. A tracker uses it to know where to look in the sky, so a device with an up-to-date almanac gets a position fix quickly and uses far less battery doing it. The almanac goes stale over time, and a tracker with an old one can take minutes to find a fix, or fail to find one at all.
Previously the only way to refresh it was to hold an NFC phone against each device. Almanac Fleet does it remotely, over the same LoRa network the devices already use, to as many devices as you like at once.
Before you start
Almanac Fleet is not switched on for everyone. If you do not see Almanac Fleet in the main menu, ask your Yggio administrator to enable Almanac Fleet access on your user account. It is a per-user setting, so it has to be enabled for each person who needs it, and you will need to sign out and sign back in before it appears.
You also need:
- Write access to every device you want to push to. Devices you can only view are rejected.
- Devices that are Sensative VSM LoRa trackers. Other device models do not accept the almanac.
- Devices connected through a ChirpStack network server. Yggio cannot send almanac messages through Netmore, Actility Thingpark or The Things Network, so devices on those are skipped with a note on the row.
How long a push takes
The almanac is about 2.5 kB, which is large for LoRa. It is split into numbered chunks and sent one at a time, and each device confirms a chunk before the next one is sent. How many chunks a device needs depends on its data rate (DR), which reflects how good its radio link is:
| Data rate | Chunks needed | Realistic duration |
|---|---|---|
| DR0 - DR2 | 52 | Hours |
| DR3 | 23 | Tens of minutes |
| DR4 | 12 | Tens of minutes |
| DR5 | 11 | Tens of minutes |
Devices at DR0 - DR2 are far from a gateway. They will get there eventually, but the transfer is slow and competes with the device's normal reporting. If you have a mixed fleet, consider setting a minimum data rate of DR3 and pushing to the weak-signal devices separately.
Pushes continue in the background. You can close the page, or your laptop, and come back later.
Starting a push
Pushes are started from your devices, not from the Almanac Fleet page. There are two ways.
Several devices at once
- Open Devices from the main menu.
- Tick the devices you want to push to.
- In the bar that appears at the bottom, choose Almanac push from Select action.
- Choose the LNS connector the devices belong to, and optionally a Minimum data
rate to leave out weak-signal devices. Leave the rest alone unless you have a reason to
change it:
- Almanac refresh interval - how long Yggio may reuse an almanac it has already downloaded before fetching a new one.
- Assist position strategy - Last known GPS position gives the tracker a hint about roughly where it is, which speeds up the first fix. Devices that have never reported a position are simply sent the almanac without a hint.
- Press Start push.
One device
Open the device, go to LoRa control, and use the GNSS almanac push section there.
Watching progress
The Almanac Fleet page lists your pushes, newest first, with the status of each one and how many of its devices are done. Press View on a row to open it.
The detail view shows each device with a status and a chunk count such as 14 / 23. Click a
device row to see per-chunk detail: which chunk is in flight, what the device confirmed, and
when.
Device statuses:
| Status | Meaning |
|---|---|
pending | Queued, not started yet |
sending gps time, sending assist pos | Sending the two small set-up messages |
chunking, awaiting ack | Transferring; waiting for the device to confirm a chunk |
retrying | A chunk was not confirmed and is being sent again |
done | The device confirmed it received and stored the almanac |
skipped | Below your minimum data rate, or on a network Yggio cannot send almanacs through; nothing was sent - the row says which |
failed | Gave up after repeated retries; see the error on the row |
The summary line also counts unconfirmed devices. These finished the transfer but never explicitly confirmed the final message, so the almanac probably arrived but Yggio cannot promise it. If a device stays unconfirmed and its position fixes are still slow, push to it again.
A push is slow by nature, and a device that is asleep or out of coverage holds up its own transfer without affecting the others. Nothing is wrong if a job sits at the same chunk for several minutes.
Stopping a push and cleaning up
Removing a push is how you stop it. On the Almanac Fleet page, tick the pushes you no longer need and press Remove selected, or press Remove all to clear the whole list at once; you can also remove the push you are looking at from its own page.
Removing a running push stops Yggio sending anything further to its devices, but messages already handed to the network operator may still arrive, so a device can be left with a partial almanac. Pushing to it again fixes that - a fresh push always restarts from the beginning.
The list keeps every push until you remove it, so it is worth tidying now and then.
If something goes wrong
| What you see | What it means |
|---|---|
| No Almanac Fleet in the menu | Access is not enabled on your account, or you have not signed out and back in since it was. Ask your Yggio administrator. |
| "Almanac fleet push is not enabled for your account" | Same as above. |
| A device is rejected when you start the push | You have view-only access to it, or it already has a push running. |
| No GNSS almanac push section on a device page | That device is not a Sensative VSM LoRa tracker, or it is not connected through a ChirpStack network server. |
Every device sits at pending | The push has not begun, or the connector cannot reach the network operator. Contact support if it does not move. |
A device is failed | It did not confirm chunks after several attempts, usually poor coverage or an offline device. Try again later, or exclude it with a minimum data rate. |