GPS World, January 2011

Know Your Options Before Choosing a Precision GNSS Receiver Jason Hamilton has more than a decade of experience working with GNSS technologies To bring some context analysis to the survey we recently sat down with Jason Hamilton Core Technology Portfolio Manager of NovAtel Inc to discuss what he sees as the crucial factors that should go into the decision making process of choosing a precision Global Navigation Satellite Systems GNSS receiver NovAtel is a leading North American manufacturer of this type of receiver and more information about its GNSS product offerings may be found online at NovAtel com What are some of the initial factors to consider when comparing the different GNSS receivers available on the market today Jason Hamilton JH Finding the right component for your system is critical to the success of your product With a wide variety of GNSS products on the market the choice can be confusing so it is very important to clearly understand what technologies are available In addition to the technical aspects of a GNSS receiver some of the factors to consider include s the functionality your application requires s the suitability of the vendor to your needs as an originial equipment manufacturer OEM and s the ease of product integration Lets start with the technical aspects JH Much depends on the application and the kind of end user product into which the receiver will be integrated Some of the specifications to keep in mind are listed in the survey but the importance of these and the trade offs between them can be complex For example trade offs between size and accuracy may need to be weighed Finding the best fit for your product requires understanding what is good enough for your application A receiver that is under featured will not suit your applications needs and an overfeatured product will not meet the cost targets for your market What differentiates receivers JH There is a wide array of receiver options available on the market today Single frequency offerings are available at low cost and provide accuracy appropriate for many commercial and consumer applications Low cost offerings are available at the chip or receiver board level depending on the needs of the application There are many vendors to choose from for a low accuracy receiver If precise positioning is needed look for products that offer multi frequency support and differential positioning modes These products tend to be at the board level and are differentiated by their physical dimensions size weight temperature range interface options UART USB Ethernet and signal tracking capabilities In addition precision receivers are differentiated by the quality and robustness of their positioning algorithms This is something that is not possible to evaluate in the receiver survey and highlights the importance of evaluating any product before you commit These differences can have a significant impact on the performance of the receiver in your application especially if the receiver has not been used in a specific application segment before Given the complexity of GNSS products the reputation of the vendor plus the support provided in terms of technical integration documentation and customer support can almost be as important as the product itself What drives the accuracy of a GNSS receiver solution JH Understanding the accuracy requirements of your application is critical to choosing the right receiver Accuracy of the solution output by the receiver is dominated by a few key factors s What satellite signals are tracked Code only receivers are limited to meter level accuracy whereas higher end receivers that provide accurate carrier phase measurements allow for cm level real time or post processed position determination s How precisely the receiver measures the satellite signals The code and carrier measurement accuracy directly correlates to the accuracy of the final solution s How well the receiver mitigates the effects of multipath Manufacturers have patented techniques to mitigate the effect of multipath on the satellite measurements A good example is NovAtels Pulsed Aperture Correlator PAC technology ADVERTORIAL