Why you should be using the Trimble SPS850 series GNSS receivers


This article originally written by PositioningSolutions.com


Over the last few years receiving RTK corrections through the internet, as opposed to UHF radios, has become a popular and cost effective way to deploy several rovers over multiple sites.

Additionally, the FCC narrowband regulations on the UHF band (450-470 Mhz), has taken a big hit on the distance a UHF radio will transmit. According to Trimble, narrow banded radios are estimated to transmit 1/3rd the distance of non-narrow band radios- not to mention the hassle of acquiring an FCC license.

And lets not forget base station theft. eBay and pawn shop shelf’s are riddled with Trimble base stations that were “found” on the side of the road.

Yes, it is easy to understand the benefits of internet based RTK corrections – and the Trimble SPS850 series (SPS850, SPS851, SPS852 and SPS855) are the best solution to the problem.

The Trimble SPS850 series receiver is a modular GNSS receiver with internal UHF or 900 Mhz radio. It can be used as either a base or rover (depending on options). It has an internal battery (10 to 12 hour), internal Bluetooth, internal user interface, and internal serial to Ethernet converter (simple internet setup) along with auto-base functionality, CMR, CMR+, CMRx and RTCM protocols. This receiver has everything! The SPS850 is so versatile and easy to set up - a caveman could do it.

The SPS850 is a modular receiver. It requires a separate GPS antenna to receive satellite signals, preferably the Trimble Zephyr Model 2 or Zephyr Geodetic. This allows you to install the SPS850 inside a jobsite trailer or vehicle – safe from the elements and thieves. These receivers also have a full-metal jacket and are totally sealed, so they can take some serious jobsite abuse.

Local Base:

As we mentioned before- the SPS850 has an optional internal transmit and receive radio. The UHF radio offerings are: 410 to 430Mhz, 430 to 450Mhz, 450 to 470Mhz. There is also a 900Mhz version. These are 2 watt radios that can easily cover small sites. The distance a radio will transmit is always dependent on terrain, obstructions and radio antenna, and antenna height – but on average we have received corrections around 1.5 miles away from the SPS850 base with either radio type. For longer distances – you can always add a high power external radio, like a Trimmark 3 or HPB450. For dual radio situations (900 and UHF) the SPS850 can transmit out of its internal radio – while also transmitting to an external one. This works great for sites where survey and construction crews are running different radio types e.g. Trimble survey and Trimble Grade Control Systems.

The SPS850 has a front panel user interface that makes base station setup easy. The receiver can be set up with a Trimble data collector running, Trimble Survey Controller, Access or SCS900. There is also an auto-base feature that works great for machine control operators. The auto-base feature will remember its position parameters from the previous setup. It allows for 1 button (the power button) operation the next day.


Internet Base:

Sending RTK corrections through the internet requires an internet connection for the base station and a cellular connection for the rovers that need to receive those corrections. The SPS850 was designed with the internet in mind. It is the easiest electronic device to set up on a network – that we have ever seen. Seriously – this thing was easier to set up than our wireless printer. It also has a web browser interface that allows you to access advanced futures like remote set up and remote troubleshooting – That’s right, you can access your base station from anywhere in the world – just open your browser and type in its IP address. Brilliant. Within 15 minutes, we had it transmitting RTK corrections over the internet….But wait – there’s more...

Another advantage of the SPS850 is that it can simultaneously transmit corrections over multiple ports, using multiple protocols. For example – you can send CMR+ corrections through the internet while sending RTCM corrections through the internal UHF radio – while also sending CMRx corrections through an external radio – or any combination of the sort. You can even have a 4th port sending via Bluetooth.

Another cool trick – two job sites – one base station:

Think about this scenario: You have multiple jobs that are close to each other, but out of radio range. The SPS850 can be located on one site, providing corrections locally – while sending corrections to the second site through the internet.

Note: Sending corrections through the internet enables your rover to receive those corrections over nearly unlimited distances. This is not the same as a VRS solution. Keep in mind that the laws of physics which control RTK accuracy are still in play here and we don’t recommend using corrections when you are more than 20 miles from your base station. The Trimble R8 GNSS Model 3 receiver specs vertical kinematic survey accuracy at 20mm + 1ppm RMS. The longer the distance is between the rover and the base – the greater the vertical error. VRS solutions are more accurate at distances over 20 miles because they are able to model the atmospheric conditions and apply advanced corrections to your location based on multiple base stations that cover a large area.

Rover operation:

The SPS850 is perfect for rover applications too. It can easily be mounted to a survey pole, tucked away in a backpack, or mounted in a vehicle – perfect for daily quantity topo’s. The SPS receivers are optimized to work with Trimble’s SCS900 software, but it can also be used with Survey Controller software ** Survey Controller requires and upgrade code – this code is usually free, but we are aware some dealerships will charge up to $250 for it.

Additional information:

SPS850 series receivers can range in price depending on the features installed. Here is what you need to know when buying one of these receivers:

SPS850 Extreme:

These were the original from back in 2005. They are 72 channel receivers that included GLONASS tracking and can be used as either a base or rover. They were offered multiple radio options: 900Mhz, 410-430 Mhz, 430-450Mhz, 450-470Mhz There is also a non radio version. Optional upgrades include: L5 and data logging.


The SPS851 is the same receiver as the SPS850, except GLONASS tracking was optional (the SPS850 included the GLONASS option).


This is a 220 channel receiver that gets confusing because everything is an option – including the accuracy. From the factory this is a “bumb” or “blank” receiver. It has no options installed and will not do anything without them. Depending on the options purchased - the receiver can either be a base or a rover – or both. GLONASS is also an option, along with L5 and data logging. To ensure you are buying a RTK accuracy unit – make sure the RTK Precise option (base or rover) is installed. This option can also be purchased at anytime, but upgrades are not cheap. If you are looking at purchasing one of these receivers – please have your local dealership verify what options are currently installed. You can also check with us.


This is the most current version, released in 2011 with an amazing 440 channels! Trimble’s spec sheet shows that this receiver will also track COMPASS and Galileo constellations (when available). The SPS855 also has a 900 Mhz option with one UHF option that covers the full 410 to 470 Mhz spectrum. Just like the SPS852, everything is an option with this receiver – so be cautious when purchasing.

Again, SPS receivers are optimized for SCS900 software, but we have successfully tested and operated them with Survey Controller ver 12.49 – with exception of the SPS855.

Trimble SPS852 GNSS

Trimble SPS852 set up on a tripod with Trimble Zephyr Geodetic II for a local base station with internal 450-470 Mhz license free radio.


Trimble NetR9

The Trimble NetR9 GNSS receiver looks the same as the SPS850 but does not have the option of internal radio and cannot be used with Survey Controller software. The NetR9 was designed for office installations - not the field.


Trimble NetRS

The Trimble NetRs receiver was the first to go online, but was difficult to set up and was a GPS receiver only. Additionally the NetRS is not a field receiver and does not have an internal radio. This receiver has a Linux operating system.


This article was written in 2016. We our put forth our best efforts to ensure accuracy of information listed. Please use this information as an additional guide to help you make a decision. As always, when spending a large sum of money, it is best practice to consult with your local Trimble dealer before making a decision to purchase. The Trimble Exchange Marketplace is a great source to find quality pre-owned Trimble products.


Find the best pre-owned Trimble GNSS VRS capable receivers - and more - on the Trimble Exchange Marketplace!

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