Topcon ERR-02 Error: What It Means and How to Fix It

Applies to: HiPer HR, HiPer V, HiPer II

What Does ERR-02 Mean?

ERR-02 on Topcon HiPer GPS/GNSS receivers means the Position Dilution of Precision (PDOP) has exceeded the configured threshold — typically 6.0 for survey-grade work. PDOP is a dimensionless number that describes the geometric quality of the satellite constellation as seen from the receiver's location. A PDOP of 1-2 is excellent (satellites well-distributed across the sky), while a PDOP above 6 indicates satellites are clustered together in one part of the sky, producing unreliable position computation even with strong signal levels.

Understanding why PDOP matters is important: position accuracy is fundamentally a geometric problem. With satellites spread evenly around the sky, small errors in measuring satellite range translate to small errors in position. With satellites clustered together (high PDOP), those same small range errors can translate to large position errors — because the triangulation math is working with nearly parallel lines of position rather than crossing lines. ERR-02 protects you from outputting coordinates that look precise but are actually inaccurate.

High PDOP typically results from physical sky obstructions — when you're in a location where a section of the sky is blocked, the remaining visible satellites may all be in one quadrant, creating poor geometry. It can also occur briefly at certain times of day when satellite orbits happen to put available constellations in poor geometric arrangements, though this is rare with multi-constellation receivers tracking 20+ satellites.

Common Causes of ERR-02

• Physical sky obstruction blocking a significant portion of the sky, forcing the receiver to use satellites that are all in one direction — common in urban canyons, deep trenches, or near tall buildings
• Elevation mask set too high — if the mask is set to 20-25 degrees instead of the standard 10-15 degrees, useful low-elevation satellites are excluded, reducing geometric diversity
• Single-constellation operation (GPS only) at a time when GPS satellites are in poor geometry for your location — enabling GLONASS, Galileo, or BeiDou provides geometric diversity
• Ionospheric or atmospheric disturbances that increase satellite signal noise, causing the receiver's accuracy filter to reject borderline satellites, reducing the effective constellation
• Time of day — while rare with multi-constellation receivers, there are occasional brief windows when available satellite geometry is suboptimal for a specific geographic region

How to Fix Topcon ERR-02 — Step by Step

1. Check MAGNET Field or the receiver's satellite display to see the current PDOP value and the sky plot. The sky plot will show clearly if satellites are clustered in one area.
2. Lower the elevation mask setting. If it's set above 15 degrees, bring it to 10-13 degrees to include more low-elevation satellites. In MAGNET Field: Settings > Rover > Satellite Tracking > Elevation Mask.
3. Enable all available constellations (GPS, GLONASS, Galileo, BeiDou) if not already active. Adding GLONASS or Galileo often breaks up clustering and improves PDOP significantly.
4. Move the antenna to a location with better sky view. Even moving 10-15 meters away from a tall building can dramatically improve sky coverage and PDOP.
5. If working in a trench or excavation, extend the range pole height or use a bipod/tripod to raise the antenna above the trench walls for better sky coverage.
6. Wait for satellite geometry to improve. PDOP changes as satellites move — a 10-15 minute wait is sometimes sufficient for geometry to improve to acceptable levels.
7. If the job site constraints prevent moving to a better location, consider whether the job's accuracy requirements can tolerate a slightly elevated PDOP threshold — RTK survey work typically requires PDOP < 4; mapping and construction layout may be acceptable up to PDOP 6.

When to Send It In for Service

ERR-02 is almost never a hardware problem — PDOP is a geometric condition, not a receiver fault. If ERR-02 appears consistently in open-sky conditions with no obstructions, the receiver's satellite tracking or PDOP calculation may have a firmware fault. Try a firmware update first; if the problem persists, service center diagnosis is needed.

Preventing ERR-02 in the Future

Plan survey points in advance using GNSS planning software (Topcon MAGNET Office, GNSS Planning Online) to identify times and locations with good satellite geometry. Set elevation masks at 10-13 degrees as a standard to maximize geometric diversity. Use multi-constellation tracking as the default configuration.

Related Topcon GNSS Error Codes

Topcon Gnss Error Err01 | Topcon Gnss Error Err03 | Topcon Gnss Error Err04