A compact, dual-constellation, network-enabled RTK rover system with GPS and Glonass capabilities.

The GRS-1 GPS + Glonass receiver is packaged in a 7.8 x 3.5 x 1.8-inch device weighing 1.5 pounds.

Topcon Positioning Systems Inc.
7400 National Drive
Livermore, CA 94551


Suggested Price List:GPS-only units are listed at $11,090. Units with GPS + Glonass start at $13,090 without the GSM or CDMA modem. The modem is an additional $400 for either the GPS-only or GPS + Glonass configuration. The optional RH-1 radio is $4,290 for digital UHF and $4,990 for the spread-spectrum or Free Channel Scan function.

Topcon is introducing this product with a zero-down and first-three-months-deferred option in a 36-, 48- or 60-month plan. For the 60-month plan, the payment works out to about $250 per month (a little more for GPS + Glonass or a little less for GPS only).

Topcon released the GRS-1 GPS + Glonass receiver on March 18. Packaged in a 7.8 x 3.5 x 1.8-inch device weighing 1.5 pounds, the GRS-1 is a compact system in the style of the GMS-2 receivers used for mapping. But that is where the similarity ends. The GRS-1 is a 72-channel receiver for GPS, optional Glonass and satellite-based augmentation systems (SBAS)--such as the Wide Area Augmentation System (WAAS) and European Geostationary Navigation Overlay Service (EGNOS)--that is capable of centimeter-level RTK, static baseline observations, RTK base station duty, differential GPS (DGPS) and, of course, autonomous positioning.

The system provides the ability to do centimeter-level RTK positioning using a lightweight system without having to invest in the equipment or the time to set up a base station.

System Specifications

I got an early look at the system with Jason Killpack, Topcon’s director of product management, while at the SPAR Conference in Denver. Before we braved the blustery cold of downtown Denver, I reviewed the package and the specifications.

The GRS-1 runs an XScale microprocessor with Windows Mobile. Topcon’s newest version of TopSURV (version 7.2.2, which was upgraded for the GRS-1) comes with it. This software not only handles all the GNSS functionality, it can also act as a controller for Topcon’s total stations and digital levels. The standard memory in the unit is 256MB of SDRAM plus 1GB of flash memory. More flash memory (up to 2GB) can be added through the SD card slot. Data transfer and additional memory are also supported through the mini-USB port, which allows the GRS-1 to act as either host or client. A 2-megapixel camera, electronic compass and built-in WiFi and Bluetooth are some of the additional niceties included in the base package.

Killpack explained that the hand-held package includes a built-in L1 antenna (for GPS and Glonass) for use in mapping applications. Surveyors can also use the antenna for autonomous navigation in their vehicles to get to the jobsite and on the ground to find geodetic or cadastral control. The hand-held unit is rated at <1 meter horizontal positioning (RMS) and <50 centimeters with the external antenna.

One of the most impressive features of the system was the small briefcase-sized package into which the complete system fits. The entire package--which includes the optional DC charger for the car, an optional extra battery and other components--weighs less than 8 pounds. If you want to use the GRS-1 as a standalone device, the only thing you need out of the briefcase, other than the GRS-1 itself, is the battery charger and possibly an extra battery or two. (Incidentally, two batteries are provided with the system, and their life varies depending on how you work in the field. Topcon says that each battery lasts five hours when doing static observations.)

If you want to do RTK observations, you’ll need to pull out the antenna cable, the bracket for attaching the unit to the pole and the L1/L2 GNSS antenna. Connect these components together on the antenna pole (the only component not packaged in the briefcase), and you’re off with a 5.9-pound rover system--one of the lightest systems on the market.

Flexibility in Action

Killpack and I grabbed our coats and went outside. Despite the fact that the unit had been last used in California and thus had to do a cold start, the GRS-1 was up and running in less than a minute. The TFT VGA color touchscreen (3.7 inch diagonal) indicated the status as it went from “float” to “fixed” in short order. That’s when more of the power of the GRS-1 came into play. The system comes with an optional built-in GSM or CDMA cellular modem. Pay the connection and data access fees, get your login information for the RTK network provider for the area, and you have the ability to do centimeter-level RTK positioning without having to invest in the equipment or the time to set up a base station.

As we walked around the block, Killpack demonstrated that the TopSURV software can be configured to automatically collect the number of epochs you desire at each point whenever you press the [Measure] key. That same software gives you the flexibility to look at your measurement statistics, the satellite constellations, DOP and signal-to-noise ratios.

For most surveyors, the flexibility of TopSURV’s display screens allows you to view the observed points in the form of plotted points with a background map or a plan that you’ve loaded into the machine. The standard software functions include stakeout using graphical or numerical guidance, topographic data collection, and a variety of route surveying and CAD functions. Finding or setting points online, doing intersections between lines and curves, and determining offsets are all included.

For a change of pace, Killpack brought up a downloadable Google Maps application for mobile devices and demonstrated how the GRS-1’s positions were used to control the location of the cursor on the map. He also demonstrated the unit’s ability to look up information on the Web with Internet Explorer and, just for grins, check his e-mail, as well. Grinning aside, when he started to take pictures of the street infrastructure with the built-in 2-megapixel camera, I realized the importance of all the available connectivity in the unit. Being able to send images, data and maps between the field and the office means increased productivity as data and information can be shared without having to revisit the field repeatedly.

The complete system fits in a small briefcase-sized package weighing less than 8 pounds.

Additional Considerations

Back inside, Killpack explained that the GRS-1 was designed by Topcon’s team of engineers from the United States, Japan and Russia, and component parts similarly come from all over the world. The unit is assembled and final-tested in the U.S. at Topcon Positioning Systems’ facilities in Livermore, Calif. Consistent with Topcon’s policies, software upgrades are available to registered users for the life of the product at no extra charge.

For users of UHF or spread-spectrum systems, the GRS-1 has a clever weatherproof expansion connector on the underside of the unit. UHF, spread-spectrum or Free Channel Scan UHF can be connected here with an optional RH-1 radio.

The pricing for the unit is attractive when you consider that it includes the entire briefcase “kit” and antenna pole. The internal GSM or CDMA modem is an additional cost for either the GPS-only or GPS + Glonass configuration. If you use correctors from a real-time RTK network, you’ll also have to consider additional monthly charges for phone company data service as well as the RTK network provider’s fees. These fees vary by providers, so you should check locally to determine your operating costs. To use the GRS-1 with beacon services, you can combine it with Topcon’s BR-1 that receives CORS signals. Bluetooth is used to transfer the correction to the GRS-1.

The unit is rated at IP66, which means that there is no ingress of dust or of water projected in powerful jets against the enclosure from any direction. It can survive a 1-meter drop and can be used in temperatures ranging from -4 F to 122 F (-20 C to 50 C) with the exception of the camera, which works down to 14 F (-10 C). The standard position update rate of the unit is 5 Hz, but options are available to speed this rate to as much as 100 positions per second.

An exceptionally lightweight, compact, self-contained system (except for the pole) with GPS and Glonass capabilities; the flexibility to transition from autonomous to DGPS to static to RTK, including accessing RTK network connections; and accuracy down to the centimeter level in the RTK mode−the GRS-1 is likely to draw a lot of users from across the geomatics spectrum due to these very attractive benefits.