RTK Accuracy Calculator
Estimate horizontal and vertical RTK positioning accuracy based on baseline length and manufacturer specifications.
Input
Result
Understanding RTK positioning accuracy
Real-Time Kinematic (RTK) GNSS positioning delivers centimeter-level accuracy by applying carrier-phase corrections from a base station to a rover receiver in real time. The accuracy you actually achieve depends on two factors: a fixed component (the receiver’s intrinsic noise) and a distance-dependent component that grows linearly with baseline length.
Manufacturers publish accuracy specifications in the form "A mm + B ppm of baseline". Typical RTK specs are 8 mm + 1 ppm horizontal and 15 mm + 1 ppm vertical. Over a 10 km baseline this translates to approximately ±18 mm horizontal and ±25 mm vertical. This calculator lets you plug in the specs of your specific receiver and any baseline to see realistic expected accuracy.
The RTK accuracy formula
For example, a Trimble R12i advertised at 8 mm + 1 ppm over a 15 km baseline gives: 8 + (1 × 15) = 23 mm horizontal error budget. This is the 1-sigma standard deviation under ideal conditions (good satellite geometry, no multipath, stable ionosphere).
Factors that degrade RTK accuracy
- Longer baselines increase ionospheric and tropospheric residual errors
- Multipath from buildings, trees, or water surfaces
- Poor satellite geometry (high PDOP, fewer than 6 satellites)
- Short occupation times (less than 10-15 seconds per point)
- Atmospheric disturbances (solar storms, scintillation)
- Antenna phase center offset and unmodeled PCO/PCV corrections
- Using float solution instead of fixed integer ambiguity resolution
rtk_calc.dop_types_title
- rtk_calc.dop_1 \u2014
- rtk_calc.dop_2 \u2014
- rtk_calc.dop_3 \u2014
- rtk_calc.dop_4 \u2014
- rtk_calc.dop_5 \u2014
Professional use cases
Topographic surveys: Verify whether a planned baseline can meet project accuracy specifications before mobilizing a crew. For a 1 cm tolerance survey with a receiver rated 8 mm + 1 ppm, baselines up to 2 km are safe.
Construction stakeout: Machine control systems require 20-30 mm horizontal accuracy. A 10-15 km baseline with modern dual-frequency GNSS is typically sufficient for earthworks.
Monitoring and deformation: Sub-centimeter monitoring requires very short baselines (under 1 km), continuous observation (hours), and post-processing rather than real-time RTK.
Cadastral surveys: Boundary determination often requires 2-5 cm horizontal accuracy. Network RTK (NRTK) through a CORS network can maintain this accuracy across large areas without long physical baselines.
Frequently asked questions
What is a typical RTK accuracy specification?
Most professional dual-frequency receivers publish 8 mm + 1 ppm horizontal and 15 mm + 1 ppm vertical. Higher-end systems with multi-constellation support can reach 5 mm + 0.5 ppm.
How does baseline length affect accuracy?
Accuracy degrades roughly linearly with baseline because ionospheric and tropospheric delays do not fully cancel between base and rover. The ppm term in the specification captures this.
What is the maximum useful RTK baseline?
Traditional RTK works well up to 20 km. Beyond that, ionospheric errors dominate and integer ambiguity resolution becomes unreliable. Use NRTK or PPP-RTK for longer distances.
Is NRTK more accurate than single-base RTK?
NRTK typically maintains similar fixed-component accuracy (~10 mm) across the entire network coverage area, effectively eliminating the ppm penalty.
Related tools and topics
See our guides on GNSS receivers, GNSS boards, and articles about RTK baseline accuracy.