> ## Documentation Index
> Fetch the complete documentation index at: https://docs.tracenav.net/llms.txt
> Use this file to discover all available pages before exploring further.

# TraceAssist Ephemeris

> Accelerate first fixes by streaming GNSS broadcast ephemerides through TraceNav

TraceAssist Ephemeris keeps rovers ahead of the broadcast ephemeris cycle. While a receiver is still acquiring satellites, TraceNav repeats the latest orbital parameters so positioning engines can start computing immediately.

## Why it matters

* **Faster first solution**: No need to wait for satellites to send their own ephemeris pages (which can take minutes).
* **Reliable cold starts**: Essential for rovers that power-cycle or move between job sites frequently.
* **Unified delivery**: Uses the same NTRIP connection as the main correction stream—no additional sockets or SDKs required.

## Broadcast behavior

| Parameter      | Value                                                                                    |
| -------------- | ---------------------------------------------------------------------------------------- |
| Interval       | Every 5 seconds                                                                          |
| Trigger        | Begins immediately after connect; stops when first valid NMEA GGA is received            |
| Constellations | GPS (1019), GLONASS (1020), BeiDou (1042), Galileo (1046)                                |
| Format         | Standard RTCM 3.x binary frames                                                          |
| Transport      | Shared with the primary TraceRouter mount; enabled by default for every TraceNav session |

<Tip>
  If your rover supports assisted positioning metadata, configure it to store the latest ephemerides. This avoids re-requesting data after short drops.
</Tip>

## Typical startup timeline

<Timeline>
  <Event title="T+0s: Connect" description="Client authenticates with TraceRouter. No GGA observed yet." />

  <Event title="T+5s: First ephemeris burst" description="RTCM 1019 / 1020 / 1042 / 1046 broadcast for all tracked PRNs." />

  <Event title="T+10s: Repeat cycle" description="Ephemerides repeat every 5 seconds until GGA arrives." />

  <Event title="T+30s: GGA received" description="Caster transitions the session to TraceVRTK corrections." />
</Timeline>

## Rover responsibilities

* **Parse & cache**: Store incoming ephemerides until a fix is achieved; most SDKs do this automatically.
* **Send GGA**: Transmit NMEA GGA sentences every 1–5 seconds once position estimates become available.
* **Validate fallbacks**: If GGA stops, TraceRouter can resume ephemeris mode (depending on configuration).

## Monitoring

Within the TraceNav dashboard:

* Open the device session detail to view *Ephemeris Mode* duration.
* Verify message counts—ephemeris bursts appear as spikes in message 1019/1020/1042/1046 graphs.

## Related docs

* <a href="/products/tracevrtk">TraceNav VRTK</a> – differential corrections after first fix
* <a href="/products/tracerouter">TraceRouter</a> – orchestrates the hand-off between ephemeris and VRTK
* <a href="/protocols/rtcm-message-map">RTCM message map</a> – decode the ephemeris message content