Best Practices for Installing Alloy GNSS Receivers

October 27, 2020

Trimble Real-Time Networks

In 2018, Trimble introduced its next generation Global Navigation Satellite System (GNSS) reference receiver for real-time network (RTN) applications—the Trimble Alloy™ GNSS reference receiver. Setting a new industry standard with 672 channels, the Continuously Operating Reference Station (CORS) receiver provides users and operators with access to multiple constellations and signals, supplying robust and reliable reference data. With an IP68 rating for protection against dust and moisture, the Trimble Alloy performs even in the most rugged environments to meet the demands of CORS network operators and earth science researchers. This new system gives high-performance and reliability to deliver high-quality GNSS data, along with unprecedented levels of usability and user convenience.

The Trimble Advanced Positioning Network Operations (NetOps) team has spent the past 3.5 years expanding Trimble’s ground-based network for Trimble CenterPoint RTX Fast, making it the “largest, high-performance GNSS correction network in the world.” (1) This expansion also included the modernization of the network, installing Trimble Alloy receivers that make it possible for users to achieve better performance and reliability by leveraging measurements from more satellite constellations. By doing so, they’ve learned a few things along the way on how to establish reliable, high performing reference stations – and it’s working. In fact, many have said the system performance is one of the best in the world.

Kicking Off a Network Expansion

“When we’re installing Alloy GNSS receivers to expand our existing network, we’re generally looking at two types of installations – building new reference stations and working together to modernize stations for network partners within existing networks,” said Matt Henigin, project manager within Trimble Advanced Positioning. “As the team searches for new installation sites, we look for a stable building made of concrete, brick or metal frame, and one that has a clear sky view with little to no metal objects around. We also look for hosts who are businesses that have a history of stability so we can ensure a long-term, mutually beneficial partnership.”

Once the NetOps team finds an installation host partner, they have a team of field engineers who perform or coordinate the installation. There are two primary components of the equipment installation – the rooftop antenna and the receiver. For the antenna installation, it is anchored to the building structure in order to be geodetically stable - meaning it is as closely affixed to the structure and the earth as possible via concrete expansion bolts or lag screws to ensure it will never move. The antenna mast is installed vertically in a place where it will receive maximum satellite signals that won’t be obstructed. The antenna is aligned to the north using an adapter with threadlocker to prevent any movement.

Next, they run a cable into the building where they install a cabinet that will house the rest of the base station components, including an Alloy GNSS reference receiver, to keep them contained and undisturbed. Once the cabinet is in place, the NetOps team installs the router to connect to the internet, working with local internet service providers – connections include everything from broadband cable to fiber optic to cellular connections – to ensure the best setup that will minimize or remove disruptions altogether. And finally, they add an uninterruptible power supply (UPS) that provides surge protection and ensures the router will have power during brief power disruptions. Alloy’s internal batteries are reserved for longer power outages.

Trimble NetOps Team’s General Tips for a Successful Receiver Installation

To ensure the Alloy GNSS reference receivers get the best satellite signal reception and data quality, here are a few best practices the NetOps team has learned along the way:

Antenna Location is the First Step: Find the highest point on the rooftop where the antenna will see the most satellites all the way to the horizon, but is also in some way shielded from metal surfaces that will reflect satellite signals (multipath). This is the best area to place an antenna to avoid receiving errant signals that could create problems.
Spectrum Analyzer Check: Alloy’s built-in spectrum analyzer is a useful tool when you have a receiver that’s not performing well but you can’t determine why. Use the spectrum analyzer to troubleshoot the issue and gather data that will help you find a better location for your receiver. Trying to troubleshoot problems with a different receiver? Temporarily replace the receiver with an Alloy and use the spectrum analyzer to see what is causing the issue. In general, one should install CORS in areas without radio interference or nearby potential jamming sources. Equipment around airports and military bases are notorious sources of potential interference.
Ensure Antenna Connections Won’t Fail: The antenna is one of the most important parts of the GNSS equation. Without it, you can’t receive the signal inputs, which are necessary to calculate GNSS measurements. The first step is to make sure all connections for antenna cables are secured using amalgamating tape. Drip loops can also help to avoid water penetration and ensure the cable won’t fail over time. Conduit can help to shield the cable from inadvertent disturbances and protect it from sun damage. Trimble antennas are designed for reliability so they can operate for years on end with minimal intervention.
Err on the High Side: When specifying internet bandwidth requirements, err on the side of higher bandwidth or install a dedicated internet connection, if possible.
Connect to the Host Backup: The Trimble NetOps team prefers to put in its own UPS, but if it’s possible to put the system in a place with an existing backup generator or battery power bank provided by the host, that may be an even better option.
Minimal Configuration is Key: When the NetOps team first started, they included built-in power failover components, extra redundancies and other complexities into the cabinet. Once they took a step back, they quickly realized the added complexity was creating more hardware failure opportunities over time. The new sites are very minimal in configuration – one power connection plus UPS backup, one internet connection, one receiver and one antenna. That’s it. Instead, the additional redundancy was moved to the overall network design, so it could withstand short duration outages at individual stations without affecting network performance.
Unique Redundancy Measures: In some applications, such as network monitoring stations, redundancy cannot be easily designed into the layout and has to be designed into the site in order to avoid downtime. At these sites, the Trimble NetOps team installs additional redundancy measures where necessary. A second internet connection for these applications is especially important - if one connection goes down, the station uses the other. The team also recommends different combinations such as broadband cable and DSL or fiber and cellular, and diverse providers to ensure there is a variety of connection types which helps to minimize potential downtime.
Avoid Metal: This one should go without saying, but sometimes needs to be repeated. The Trimble NetOps team strongly recommends installing the antenna away from any metal objects – vents, air handlers, TV satellite dishes, piping or even overlooking a parking lot filled with metal reflective surfaces. However, knowing this isn’t always possible, Trimble has the Trimble TI Choke Ring Antenna – an antenna with a series of metal rings around the base that filters out the reflected multipath signals and keeps signals bouncing off other structures from interfering with the performance of the base station. The choke ring antenna can potentially make challenging locations more viable in the absence of a better antenna location.

With these best practices in mind, Trimble's Alloy GNSS reference receiver continues to outperform many competitors and is a leader in the marketplace. If you’re ready to update your RTN network with Trimble Alloy reference receivers, contact your authorized Trimble dealer or visit https://www.trimble.com/Real-Time-Networks/Trimble-Alloy.aspx.