# GNSS machine guidance and surveying in construction A GNSS receiver on a construction machine determines its position from satellite signals. Corrections from reference stations, used in real-time kinematic positioning (RTK), raise the accuracy to the centimetre level. Machine guidance shows the operator where to work, and machine control automates parts of the machine's operation. Surveyors use the same technology for precise measurements on site. ## How it works GNSS stands for global navigation satellite systems such as Galileo and GPS [1]. A receiver on the machine determines its position from the satellite signals. Galileo improves positioning accuracy in urban canyons when used in multi-constellation receivers, because the additional satellites increase visibility and measurement redundancy [1]. In construction, three components work together [2]: - **Positioning**: GNSS receivers, supported by base stations as reference points, determine the exact position of the machine. Inertial sensors track its movements and add precision. - **Machine guidance**: a display gives the operator real-time guidance and feedback, so the machine follows the design. - **Machine control**: the system automates the operation of the machine based on GNSS data, for example the height of a blade. EUSPA describes this combination as the 3D machine guidance system and names RTK positioning as the basis of precise heavy machinery operation [2]. Receivers built into heavy machinery enable precise operations during construction, and in the selection and planning phases GNSS RTK is the preferred solution because it saves costs through reduced field expenses [2]. How satellite positioning works in general is explained in [what is GNSS](https://leto.space/knowledge/gnss/). ## Corrections: RTK, PPP and Galileo HAS Correction data raise the accuracy of a receiver. The three main methods compare as follows: | Method | How it works | Accuracy | | ------------------------------- | --------------------------------------------------------------------------------- | -------------------------------------------------- | | RTK (real-time kinematic) | Corrections from a base station or a network of reference stations | Centimetre level | | PPP (precise point positioning) | Corrections for satellite orbits, clocks and biases, without a local base station | Needs a longer convergence time for high precision | | Galileo High Accuracy Service | Free PPP corrections worldwide, via the Galileo signal and the internet | Typically below 25 cm horizontally | Sources: EUSPA market report for RTK and the convergence time of PPP [2]; EUSPA for the PPP corrections of Galileo HAS, in initial service since January 2023 [3]; European GNSS Service Centre for its status: the full service is still in preparation [4]. Galileo HAS provides free, global decimetre-level positioning without reliance on local correction networks; it does not replace RTK for centimetre-level work [1]. **Figure:** A base station sends RTK corrections to the GNSS receiver on the machine; a display guides the operator, and machine control sets, for example, the blade height. At the antenna, RTK reaches centimetre level, while Galileo HAS typically stays below 25 cm horizontally. Schematic drawing. ## What you get - machines that follow the digital design, with guidance on the display or automatic control - positions with centimetre-level accuracy when RTK corrections are available [1] - semi-automatic or fully automatic machine operation, with GNSS data fed directly into the hydraulic control [1] - precise surveying with the same receivers and RTK corrections [1] - the location, movement and performance of equipment for site managers, and designated areas that reduce the risk of accidents [2] - high-accuracy positions of construction assets that feed building information models [1] ## Limits **Limits** - **Sky view needed:** GNSS needs a clear view of the satellites. Buildings create urban canyons that degrade accuracy; systems that fuse GNSS with LiDAR, cameras and inertial sensors keep centimetre-level accuracy even there \[1]. Inside tunnels and buildings, satellite positioning does not work on its own. - **Corrections must be available:** Centimetre accuracy depends on RTK corrections from a base station or a network \[1]. Where there is no network coverage or no mobile link to receive the corrections, a site needs its own base station. - **Signals can be disrupted:** GNSS signals can be jammed or spoofed. For machine guidance in mining, EUSPA notes that Galileo's integrity monitoring and authentication protect against such attempts and can enhance safety \[1]; its authentication service OSNMA has been operational since July 2025 \[5]. How to protect operations is the topic of protecting GNSS-dependent operations. ## How we help We help you write the [requirements](https://leto.space/consulting/procurement/): accuracy per task, correction source, Galileo support, interfaces to your design and BIM data. In [implementation](https://leto.space/consulting/implementation/) we run a pilot on one site with KPIs such as time, material use and rework. The marketplace on [Spacegraph](https://leto.space/spacegraph/), our discovery platform, has an industry category for construction and engineering. ## Related use cases - [Monitoring construction progress](https://leto.space/use-cases/construction-progress/): Satellite images that show how a site develops. - [Protecting GNSS-dependent operations](https://leto.space/use-cases/gnss-resilience/): Jamming, spoofing and how to keep positioning trustworthy. - [Construction and real estate](https://leto.space/industries/construction-and-real-estate/): All use cases for construction, infrastructure and real estate. ## Frequently asked questions ### How accurate is GNSS machine guidance? With RTK corrections from a network of reference stations, GNSS reaches centimetre-level accuracy, which enables precise surveying and machine guidance [1]. The free Galileo High Accuracy Service raises the accuracy of Galileo to sub-metre levels, typically below 25 cm horizontally in nominal conditions [3]. It has been in initial service since January 2023, and the full service is still in preparation [4]. That suits some tasks; work that needs centimetres relies on RTK. ### Do we need our own base station? Not always. Correction data can come from a base station on site or from an RTK network. In Europe, most RTK providers have upgraded or have started to upgrade their services to Galileo [2]. Which option fits depends on the size and location of your sites and on the coverage of networks there. ### How do we start? Start with one machine type and one task, for example grading, and compare time, material use and rework with a conventional crew. Check correction coverage on your typical sites before you buy. Our [consulting overview](https://leto.space/consulting/) shows the path from the problem to operation. ## Sources 1. [EU Space Market Report 2026, Issue 1, EU Agency for the Space Programme (EUSPA), 2026-05-26](https://www.euspa.europa.eu/sites/default/files/documents/EU_Space_Market_Report_2026.pdf) 2. [EUSPA EO and GNSS Market Report, Issue 2, 2024, EU Agency for the Space Programme (EUSPA), 2024](https://www.euspa.europa.eu/sites/default/files/external/publications/euspa_market_report_2024.pdf) 3. [Galileo High Accuracy Service goes live!, EU Agency for the Space Programme (EUSPA), 2023-01-24](https://www.euspa.europa.eu/newsroom-events/news/galileo-high-accuracy-service-goes-live) 4. [Galileo High Accuracy Service (HAS), European GNSS Service Centre (GSC), operated for EUSPA, accessed 2026-10-07](https://www.gsc-europa.eu/galileo/services/galileo-high-accuracy-service-has) 5. [From Testing to Operations: Galileo OSNMA Service Now Available to Users, EU Agency for the Space Programme (EUSPA), 2025-09-05](https://www.euspa.europa.eu/newsroom-events/news/testing-operations-galileo-osnma-service-now-available-users) Page: