Alpha 4i RTK GNSS Rover Base Set with IMU and Controller

Independent RTK Rover and Base System

The Alpha 4i Rover Base Set gives field teams the equipment needed to create their own local centimetre-level RTK correction system. One Alpha 4i receiver is installed as the base station over a known or established position, while the second receiver is used as the rover. Corrections are transmitted from the base to the rover through the receivers’ internal UHF radios.

This setup is useful on construction sites, rural projects and temporary survey areas where mobile coverage or an NTRIP correction service cannot be relied upon. It also gives users greater control over the position of the base, the working area and the correction link used for the project.

Complete Equipment for Field Deployment

The set combines two Alpha 4i GNSS receivers with an Alpha B55 data collector, DiMap Pro surveying software, a telescopic survey pole and controller bracket. A tripod, tribrach and adapter are included for stable base-station installation.

Bringing these components together in one package makes the system suitable for teams that need a complete RTK setup rather than a rover that depends entirely on an external correction network. The controller and software are used to configure the receivers, establish the base, monitor the RTK solution, collect measurements and set out design points.

1,408-Channel Multi-Constellation GNSS

Each Alpha 4i receiver uses 1,408 channels to track GPS, GLONASS, Galileo, BeiDou, QZSS, SBAS and NavIC signals across multiple frequencies. Access to a broad range of signals gives the system more satellites to work with throughout the day.

For the operator, this can support more dependable positioning when the view of the sky is partly restricted by buildings, trees, machinery or nearby terrain. Satellite availability, multipath and radio conditions still affect performance, so important measurements should always be checked against site control and the reported RTK solution quality.

Centimetre-Level RTK Surveying

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 makes the rover and base set suitable for common professional tasks including topographic surveys, construction layout, infrastructure measurement, utility mapping, earthwork checks and ground control point collection.

The ppm component means that a small distance-dependent allowance is added as the separation between the rover and base increases. Keeping the base reasonably close to the working area and installing it in a clear, stable position helps achieve the best practical results.

IMU Tilt Compensation for Restricted Points

The rover receiver includes an IMU that compensates for pole tilt. Instead of carefully levelling the pole for every measurement, the operator can reach points beside walls, fences, kerbs, excavations, vegetation and other obstructions while the software calculates the position at the pole tip.

The manufacturer states approximately 2 cm tilt-measurement accuracy at a 60° pole angle and an operating range extending to 120°. In normal fieldwork, the main benefit is a faster and more comfortable workflow when measuring locations that are difficult to occupy with a vertical pole.

Integrated UHF Base to Rover Communication

Both receivers contain a 1 W UHF transceiver operating across the 410–470 MHz band. The radios support commonly used protocols including TrimTalk, TrimMark, SOUTH and SATEL formats, helping the system work with a range of compatible RTK equipment.

The stated internal radio working range is up to approximately 3 km under suitable conditions. Actual range depends on terrain, buildings, vegetation, antenna height, interference and permitted radio settings. For larger areas, the receiver can also be used with a compatible external radio where local regulations allow.

DiMap Pro Field Surveying Software

DiMap Pro is an Android surveying application for configuring the GNSS equipment and completing measurement work in the field. It includes separate rover, base and static operating modes, allowing the same software to manage the complete two-receiver system.

Survey functions include point collection, detail surveying, control-point work, point and line stakeout, road stakeout, CAD mapping, CAD stakeout, DSM stakeout and utility-related workflows. Project tools are available for coordinate systems, localization, point calibration, code libraries, grid-to-ground settings and data import or export.

This range of functions allows construction workers to set out coordinates and lines, surveyors to collect coded detail, GIS teams to record assets and drone operators to measure ground control points. CAD and survey data can be moved between field and office workflows using commonly used formats such as CSV, DXF and KML.

Alpha B55 Data Collector

The included Alpha B55 controller provides a dedicated field interface for DiMap Pro and the connected GNSS receivers. Its physical keyboard can be useful when working with gloves or entering point names and codes repeatedly. Mobile connectivity also allows the controller to access internet-based correction services when the system is used as a network rover instead of a local base and rover pair.

The controller therefore gives the set two practical correction workflows. Crews can use the included base where no network is available, or connect the rover to an NTRIP service when that is more convenient for the project.

Compact and Durable Receiver Design

Each Alpha 4i receiver measures approximately 98 mm by 53 mm and weighs 380 g. The low weight reduces the load at the top of the rover pole and makes both receivers easier to transport between projects.

The housing uses a reinforced aluminium-alloy structure with a signal-transparent top section. It is rated IP67 against dust and temporary water exposure and is specified to resist a 1.5 m drop under stated test conditions. The operating-temperature range is listed as −30°C to +70°C, supporting use across a wide range of outdoor working environments.

Battery Performance for Rover and Base Work

Receiver operating time varies according to the selected communication mode. The stated figures are up to 18 hours in network mode, 15 hours while receiving UHF corrections and 8 hours while transmitting as a radio base. Temperature, radio power, battery age and receiver settings can reduce practical working time.

USB Type-C charging and support for external power make it possible to extend operation during longer projects. For full-day base use, an external power source can be especially useful because transmitting corrections requires more energy than rover reception.

Typical Applications

• Topographic and detail surveying
• Construction positioning and stakeout
• Road, utility and infrastructure projects
• Earthwork, grade and elevation checks
• GIS asset and feature collection
• Ground control points for drone surveys
• Remote projects without dependable NTRIP coverage

When to Choose a Rover Base Set

A rover and base set is the practical choice when the working area does not have a suitable correction network, when mobile data coverage is unreliable or when the user wants direct control over the project base station. It is also suitable for contractors who move between different countries or regions where correction-service availability varies.

Projects that are always completed within a dependable RTK network may only require a rover set. A two-receiver package offers greater independence, but it also requires the base to be installed securely, configured correctly and assigned reliable coordinates before work begins.

Configuration and Support from Global GPS Systems

Global GPS Systems can help configure the Alpha 4i Rover Base Set for the required radio frequencies, correction protocol, coordinate system and field workflow. The included controller, software and mounting accessories can also be adjusted where a different pole, tablet or data-collection arrangement is preferred.

This support helps surveying companies, construction teams, GIS users and drone operators start with a setup suited to their actual projects while retaining the flexibility to work with either a local base station or an available RTK correction network.