GNSS

Why GPS signal shifts in the field and how to reduce measurement error

10 min read June 25, 2026

A GPS point can wander on screen even while you stand still. Satellite geometry, reflections, receiver quality and field method all affect the result.

Field takeaways

Phone GPS is useful for reconnaissance, not precision stake-out alone.
Trees, buildings, vehicles, fences and valley edges can cause multipath.
Waiting and repeating observations helps reduce gross mistakes.
RTK work needs fixed or float status, satellite geometry and antenna height checks.
MapLab Survey helps record method, photos and layer context.

How GPS shift appears

The simplest sign is a point that keeps moving on the screen while you are standing still. The more dangerous case is a point that looks stable but is actually several meters away from the real position. That is why one observation should not be trusted blindly in field work.

Field conditions that increase error

Trees, buildings, high walls, metal roofs, nearby vehicles, narrow valleys and steep slopes can disturb GNSS signals. When the signal reaches the receiver after reflecting from a surface, the measured position can shift. Survey crews usually describe this as multipath.

Field checks

Choose a location with as much open sky as possible before saving a point.
Let the position settle for a few seconds instead of recording immediately.
Measure the same point again and compare the difference.
If RTK is used, record whether the solution is fixed or float.
Add a photo and note when a point is suspicious or taken under poor conditions.

Realistic expectation

A field boundary drawn with a phone can be very useful for quickly understanding occupation, access or approximate area. For legal boundary work, construction stake-out, site axes or centimetre-level delivery, the workflow needs a suitable GNSS receiver, correction data, control points and disciplined field procedure.

In the field · MapLab Survey

Measure, check and deliver in the right format.

MapLab Survey is a mobile field app for RTK/GNSS points, drawings, area/volume calculations, coordinate conversion and export to DXF, KML/KMZ, GeoJSON and CSV. Capture, calculation and export can work offline; live NTRIP corrections and online basemaps need connectivity.

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Frequently asked questions

Why does GPS shift?

Because of satellite geometry, multipath, obstructions, receiver quality and method.

How accurate is phone GPS?

It depends on field conditions.

Does RTK fixed remove all error?

No. It still needs field checks.

How does MapLab Survey help?

It keeps observations, notes, photos and layers together.

Technical references

The field guidance in this article is aligned with the technical and official references below.