RTK Fix keeps dropping — how to fix it

When an obstruction passes between your antenna and satellites, signals drop. If enough satellites disappear simultaneously, carrier phase ambiguities can no longer be maintained and Fix drops to Float. This is the most common cause of Fix instability in field conditions.

• 1
  Walk with the antenna as high as possible. A taller pole (2.0 m rather than 1.5 m) gives the antenna a better line of sight over low obstacles.
• 2
  Hold the pole vertical. Even a small tilt toward a tree or building blocks the opposite side of the sky. Use the bubble or tilt sensor on your receiver.
• 3
  Reduce the elevation mask to 10°. This allows signals from low-elevation satellites that are not blocked by the obstacle to compensate for lost high-elevation signals. Do not go below 5° — multipath increases sharply.
• 4
  Enable all available constellations (GPS, GLONASS, Galileo, BeiDou). More total satellites means losing a few to obstruction matters less.
• 5
  Move your measurement position slightly — even 2–3 metres can open a different sky quadrant and restore Fix.

Multipath occurs when satellite signals bounce off surfaces before reaching your antenna. The reflected signal arrives slightly later than the direct signal. Your receiver receives both, and the mixture corrupts the carrier phase measurement — causing Fix to degrade or drop.

Multipath is worst near large metal structures (construction sites, silos, greenhouses), glass buildings, still water and wet horizontal surfaces after rain.

• 1
  Move at least 5–10 metres away from reflective surfaces. The multipath effect drops off rapidly with distance.
• 2
  Raise the elevation mask to 15° or even 20° near buildings. Low-elevation satellites have the longest signal path and are most affected by multipath from vertical surfaces.
• 3
  Use a receiver with built-in multipath mitigation (Trimble Maxwell chips, NovAtel STROBE correlators, Septentrio AIM+). These reduce — but cannot eliminate — multipath effects.
• 4
  Avoid measuring immediately after rain on flat surfaces — wet concrete, asphalt and soil reflect signals strongly. Wait 30–60 minutes after rain for reflectivity to reduce.
• 5
  If working near a construction crane or moving vehicle, wait for it to move out of the reflection zone before measuring critical points.

When the NTRIP correction stream is interrupted — even for a few seconds — your receiver loses the reference data it needs to maintain carrier phase lock. If the gap is long enough, Fix drops to Float and the receiver must re-initialise. This is especially common in areas with variable mobile data coverage.

• 1
  Check signal strength. Watch the mobile data indicator on your device while Fix is dropping. If signal fluctuates from 4G to 3G or from 3G to Edge, internet instability is the cause.
• 2
  Switch to a dedicated hotspot. Using a separate mobile hotspot device (not phone tethering) provides a more stable connection. Hotspots prioritise data stability over power saving.
• 3
  Switch carrier. Coverage maps differ significantly between carriers. If one carrier has poor coverage in your working area, try a SIM from a different network.
• 4
  Force 4G only. On Android devices, set the network mode to LTE only. Switching between 4G and 3G creates brief connection gaps that interrupt the NTRIP stream.
• 5
  Enable auto-reconnect. In your NTRIP client settings, enable automatic reconnection. When the connection drops, the client re-establishes it immediately rather than waiting for you to tap reconnect.
• 6
  Check bytes per second. In your NTRIP client's status view, watch the bytes/second counter. It should show a steady 500–2000 bytes/sec. Repeated drops to 0 bytes/sec confirm internet interruption as the cause.

At longer baselines the ionosphere and troposphere introduce differential errors that make carrier phase ambiguity resolution harder to maintain. Fix is more fragile — small signal disturbances that would not matter at 5 km baseline cause Fix to drop at 40 km.

• 1
  Switch to a VRS mountpoint. VRS generates a virtual reference station near your location, effectively reducing the baseline to 1–2 km regardless of where the physical stations are. This is the single most effective fix for long-baseline instability.
• 2
  Check which physical station you are connecting to. Load the sourcetable and look at the distance column. If you are connecting to a station 50+ km away and VRS is available, switch immediately.
• 3
  Enable multi-constellation. More satellites means more redundancy. At long baselines, losing a few satellites to atmosphere has less impact when you have 30+ satellites tracked across four constellations.

Even with a good NTRIP connection and short baseline, Fix can drop if the satellite geometry is poor (PDOP above 4–5). Satellite geometry changes continuously throughout the day — a 20-minute window of poor geometry can cause Fix to drop repeatedly even though everything else is fine.

• 1
  Check PDOP in your field software. Look for the satellite quality or PDOP display. If PDOP is above 4, consider waiting for the geometry window to pass (typically 15–30 minutes).
• 2
  Enable all constellations. Adding GLONASS, Galileo and BeiDou distributes satellites across more sky positions, dramatically improving PDOP.
• 3
  Use a satellite prediction app. Apps such as GNSS View or Geo++ RINEX Logger show predicted PDOP values for your location throughout the day. Plan work sessions around the best geometry windows.
• 4
  Lower the elevation mask slightly. Allowing 10° satellites instead of 15° adds more satellites at varied positions, often improving PDOP by 0.5–1.0 in open sky.

Default receiver settings are conservative. In challenging environments — near buildings, under trees, with long baselines — tweaking specific settings can dramatically improve Fix stability.

• 1
  Switch from continuous to fix-and-hold ambiguity mode. Continuous re-initialisation mode drops Fix at the slightest ambiguity uncertainty. Fix-and-hold maintains Fix through brief disturbances. In Emlid Flow: Settings → GNSS → set Ambiguity resolution to Fix-and-hold.
• 2
  Enable all satellite constellations. GPS alone gives 8–12 satellites. Adding GLONASS, Galileo and BeiDou gives 30–50+. More satellites = more redundancy = more stable Fix.
• 3
  Reduce update rate. Running at 10 Hz or 20 Hz in a challenging environment processes more data but also amplifies noise. Dropping to 5 Hz or 1 Hz gives the RTK engine more time per epoch and can improve Fix stability.
• 4
  Check minimum satellite count. Some field software rejects Fix if fewer than 5 satellites are tracked. In challenging environments, lowering this threshold to 4 prevents unnecessary Fix drops when one satellite briefly disappears.