Trimble E102 Error: What It Means and How to Fix It

Applies to: Trimble R10, R12i, R8s GNSS rovers

What Does E102 Mean?

E102 Fixed Solution Lost on Trimble GNSS rovers means the carrier-phase integer ambiguity solution that defines a fixed RTK position has been disrupted. The rover is still receiving corrections from the base (E101 is not active), but something has disrupted the continuous carrier-phase tracking needed to maintain a fixed solution.

Unlike E101, where corrections are absent, E102 occurs while corrections are actively being received. The rover falls to float mode — corrections are being applied, but without fixed integer ambiguities, position accuracy degrades to 0.3-1.0 meter rather than the 10-25mm of a fixed solution.

Fixed solution loss (cycle slips) happens when the carrier-phase signal is temporarily broken — by a physical obstruction, antenna motion, or signal interference — and the receiver cannot immediately re-resolve the integer ambiguities.

Common Causes of E102

• Antenna passed under an obstruction — tree, bridge, building edge — causing a cycle slip in carrier-phase tracking
• Antenna moved too fast — rapid motion during walking or vehicle-mounted use
• Multipath from a nearby metal surface or building face disrupting carrier tracking
• Ionospheric disturbance — rapid signal delay changes during geomagnetic storm
• Satellite set — a key satellite tracked for the fixed solution moved below the elevation mask
• Significant baseline increase — rover moved too far from the base station for the existing integer solution to remain valid

How to Fix Trimble E102 — Step by Step

1. Stop moving and hold the antenna steady at an open-sky location for 1-3 minutes. Most fixed solutions reacquire automatically within this time.
2. Move away from nearby metal structures, vehicles, and building faces to reduce multipath interference.
3. Check Trimble Access for the current PDOP value. If PDOP is above 4.0, wait for geometry to improve before recording measurements.
4. Verify the baseline length is within the expected operating range. If the rover has traveled far from the base, consider repositioning the base or switching to a CORS network.
5. Confirm the age of corrections is under 5 seconds. Stale corrections contribute to fixed solution loss.
6. Power cycle the rover if the fixed solution does not reacquire within 5 minutes in a clear-sky location.

When to Send It In for Service

E102 is a field condition issue in most cases. If fixed solutions consistently last only seconds even in ideal conditions with short baselines, contact an authorized Trimble dealer to evaluate the receiver's carrier-phase tracking performance.

Frequently Asked Questions

How long does it take to reacquire a fixed RTK solution after E102?

In an open-sky location with corrections active, reacquisition typically takes 30-90 seconds. If multipath, long baseline, or poor geometry is present, it may take 3-5 minutes. Power cycling speeds up reacquisition in some cases.

Can I record a measurement in float mode after E102?

Float mode accuracy (0.3-1.0m) is not suitable for construction layout or precision survey work. Always wait for fixed solution confirmation before recording measurements. Some projects permit float measurements for GIS or reconnaissance — verify your project specifications.

Why does my rover lose fixed solution every time I walk near a building?

Buildings reflect GNSS signals (multipath), which disrupts carrier-phase tracking and causes cycle slips. The fixed solution drops whenever the reflected signals interfere with the direct signals. Keep the antenna as far from building faces as possible and move away before recording measurements.

Related Trimble Error Codes

Trimble GNSS E101 No Corrections | Trimble R12i GNSS Receiver