Which GPS Receiver Matches Your Project or Prototype? A Look at 3



A new wave of GPS receivers has arrived.

As the Internet of Things (IoT) flourishes beyond the office and home, inexpensive sensors and modules—including professional and automotive grade GPS units—provide a wealth of opportunities for embedded projects on the go. While GPS receivers can be purchased for as little as $25, these devices vary largely in sensitivity and accuracy. Developers may need a high level of software and hardware maturity to optimize these modules for their product designs.

Figure 1:  The Reach RTK Kit. (Courtesy Emlid Limited)

Figure 1: The Reach RTK Kit. (Courtesy Emlid Limited)

For those of us who don’t have the resources to develop our own GPS receivers, there is a new wave of accessible and cheap GPS receivers being introduced into the market for UAVs, drones and autonomous robots. Three recent examples include the Reach Real Time Kinematics (RTK) GPS receiver (Figure 1), the Piksi RTK GNSS receiver and the Gumstix Pre-GO series of GNSS receivers. Moreover, all three of these open source devices offer up to centimeter-level accuracy with support for real-time kinematics (RTK) technology.

Figure 2: Piksi Real-Time Kinematics (RTK) GNSS receiver. (Courtesy Swift Navigation)

Figure 2: Piksi Real-Time Kinematics (RTK) GNSS receiver. (Courtesy Swift Navigation)

Reach RTK GPS Receiver

The Reach RTK GPS receiver, developed by the Emlid Reach program, is based on the uBlox Neo-M8T GNSS receiver and receives signals from GPS, GLONASS, BeiDou and QZSS satellites. The Reach runs an open-source RTK processing software written by Tomoji Takasu called RTKLIB and uses the Intel Edison as its processing unit. The unit also has an internal IMU, WiFi GNSS, Bluetooth 4.0 and a USB OTG. It comes flashed with a custom Yocto Linux image with pre-installed RTKLIB.  Boasting a small form factor of 26mm x 36mm, the receiver’s range is 10km and delivers centimeter level precision down to 2 cm. The Reach RTK GPS receiver is currently available as part of a kit that includes two GPS receivers and peripheral cables and antennas.

Piksi RTK GNSS Receiver

The Piksi RTK GNSS receiver, developed by Swift Navigation, is based on the Maxim MAX2769 GPS receiver and receives signals from GPS, GLONASS, and Galileo satellites. An ARM Cortex-M4 microcontroller acts as its processing core and has a pre-programmed SwiftNAP that contains fully programmable correlators. The Piksi comes with an integrated patch antenna, as well as an external antenna input provided by an SMA connector. A micro-USB socket provides USB connectivity to capture and transmit raw data. Taking up only 53mm x 53mm, the Piksi also delivers centimeter level accuracy using RTK technology.

Gumstix Pre-Go GPS Receivers

Providing similar functionality to the Reach RTK and Piksi RTK, the Pre-Go GPS receivers offer two levels of accuracy. First, there is the Pre-Go based on the uBlox Neo-7M, delivering the standard ∓ 2.5 meter accuracy. Second, there is the Pre-GO PPP, based on the Neo-7, which can deliver up to centimeter level accuracy by taking advantage of RTK technology. This means that the Pre-Go receives GPS satellite signals while the Pre-Go PPP receives either GPS and GLONASS satellite signals. The Pre-Go series comes with either an integrated patch antenna or with an SMA connector for an external antenna. The Pre-Go series are extremely compact at 30mm x 21mm, allowing for ease of integration onto any carrier board using a 5-pin connector.

Figure 3: Gumstix Pre-Go GPS receivers

Figure 3: Gumstix Pre-Go GPS receivers

Comparison

What great about Emlid Reach Program’s Reach RTK and Swift Navigation’s Kickstarter project Piksi is not only do both boast a high level of sensory sophistication, but that both products come ready with their own boards with an able CPU right out of the box. Both devices also have active communities, meaning that developers can make use of a wide network of engineers to help get their products to market. With the Pre-Go series, developers can connect their inexpensive Pre-Go receivers to a separately purchased computer-on-module (COM) via SMA or UART connections, Gumstix AeroCore 2 Product Suite. Gumstix engineers fully support Yocto Linux for the company’s Overo series of COMs. With a little assembly, this means that developers can build an inexpensive small form factor board with both an RTK-capable GPS receiver and a powerful COM with WiFi and Bluetooth.

GPS Module Comparison

Gumstix_Table1

For more factors to consider when choosing a module click here.

Conclusion

The Reach RTK, Piksi and Pre-Go receivers all represent the best GPS receivers available to makers and developers under the $1000 mark. For hobbyists and makers who want a product that works out of the box, the Reach and Piksi provide reliable options. For developers and makers who want some more flexibility for their projects, the Pre-Go series of GPS receivers, along with Gumstix’s line of COMs and expansion boards, provide a rapid and cost effective solution to their GPS-themed projects and prototypes.


Frech_HeadshotChristopher French is a contributing editor at Gumstix, Inc. He received his PhD from the University of British Columbia and has interests in DIY computing, engineering design and programming.

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