Alpha 4i Compact RTK GNSS Receiver with IMU Tilt

Compact RTK GNSS for Everyday Surveying and Construction Work

The Alpha 4i combines professional RTK positioning with a small and lightweight receiver body. At approximately 380 g, it is easy to carry between survey points and places less weight on the pole during long working days. This makes it suitable for surveyors, construction teams, GIS technicians, utility contractors and other professionals who regularly collect or set out accurate coordinates.

The receiver can be used as a network rover with NTRIP corrections or as part of a local base and rover setup. Its internal UHF transceiver supports common radio protocols and operates across the 410–470 MHz band, giving teams flexibility when working on sites without a convenient mobile correction service.

Multi-Constellation and Multi-Frequency Signal Tracking

With 1,408 channels, the Alpha 4i tracks GPS, GLONASS, Galileo, BeiDou, QZSS, SBAS and NavIC signals. Access to several constellations and frequencies gives the receiver more satellites to work with throughout the day. In practical terms, this can improve satellite availability and support faster, more stable RTK positioning when parts of the sky are obstructed by buildings, trees or site machinery.

The compact 8 cm full-frequency antenna uses a four-feed-point design and a wide reception pattern. It is intended to provide dependable signal tracking without requiring the larger antenna housing commonly found on traditional GNSS receivers.

IMU Tilt Compensation for Faster Point Collection

The integrated inertial measurement unit allows the survey pole to be tilted while measuring. Operators therefore spend less time carefully centring and levelling the pole for every point. This is especially useful beside walls, at building corners, near fences, on slopes or when the point itself is difficult to stand directly above.

The IMU operates at an update rate of 100 Hz and supports a wide tilt range. For normal fieldwork, this means the receiver responds quickly as the pole moves and helps maintain an efficient workflow during topographic surveys, construction stakeout and GIS data capture.

Centimetre-Level RTK Positioning

The Alpha 4i is specified for RTK accuracy of ±(8 + 1 ppm) mm horizontally and ±(15 + 1 ppm) mm vertically under suitable operating conditions. This level of performance supports common professional tasks such as measuring site features, setting out foundations and utilities, recording asset locations, checking elevations and collecting control or detail points.

Actual field accuracy depends on factors such as correction quality, satellite geometry, radio or mobile coverage, multipath, nearby obstructions and correct surveying procedures. The receiver provides the tools required for accurate RTK work, while the operator remains responsible for checking fix status and measurement quality.

Flexible Correction and Communication Options

For network RTK work, the receiver can connect through a compatible controller or Android device using Bluetooth. Where a local base station is preferred, the built-in 1 W UHF radio can transmit or receive corrections over the 410–470 MHz frequency range. The specified local radio working range is up to approximately 3 km in suitable conditions, while compatibility with an external radio allows longer-range configurations where permitted.

Support for established communication protocols helps the Alpha 4i fit into mixed equipment fleets and existing surveying workflows. Before combining equipment from different manufacturers, users should confirm matching frequencies, protocols, channel spacing and regional radio regulations.

Designed for Demanding Field Conditions

The receiver housing combines a signal-transparent top cover with an aluminium-alloy reinforced structure. It is rated IP67 for protection against dust and temporary water exposure and is designed to withstand a 1.5 m drop under stated test conditions. The specified operating temperature range of −30°C to +70°C supports work across a broad range of climates and seasons.

A USB Type-C connection is provided for charging and data transfer, and the receiver supports external power-bank operation. Battery endurance is specified at up to 18 hours in network mode, 15 hours while receiving radio corrections and 8 hours while transmitting corrections. Working time will vary with temperature, radio use, battery condition and configuration.

Field Software and Data Handling

The Alpha 4i can be operated with DiMap surveying software on a compatible controller or Android device. The software supports common field operations such as base and rover configuration, point measurement, stakeout, basemap display and record management. Data can be exported in commonly used formats including CSV, DXF and KML, helping measurements move into CAD, GIS and office-processing workflows.

Typical Applications

• Topographic and detail surveying
• Construction layout and stakeout
• Road, utility and infrastructure projects
• GIS asset and feature collection
• Earthwork checks and volume surveys
• Boundary and cadastral fieldwork where local regulations permit
• Ground control point measurement for drone mapping

Choosing the Right Alpha 4i Configuration

The receiver can be configured for use with an RTK correction network, as a rover in a local base and rover system, or as part of a complete field kit with a controller, pole and accessories. The best configuration depends on the available correction service, required working range, data-collection software and the type of work being completed.

Global GPS Systems can help buyers compare rover-only, base and rover, controller and radio options so the equipment matches the intended workflow. This is particularly useful for teams replacing an older GNSS system, combining equipment from different brands or selecting their first professional RTK setup.