Low cost GNSS receivers for positioning and monitoring applications.

The evolution of Global Navigation Satellite Systems (GNSSs) has already shown the wide range of applications that can be used and the revolutionary impact that has brought on positioning performance. Besides the increased number of satellites, every improvement in the accuracy of GNSS-based positioning has come with improvements in timing accuracy as well1.

Usually, GNSS geodetic receivers can provide results with accuracies at the millimeter level: however, they are very expensive and the risk of damage and loss is discouraging. Some consumer-grade low-cost GNSS receivers can achieve centimeter-level accuracy and facilitate the systematic application of GNSS technology in monitoring projects2.

Presently, low–cost GNSS receivers have been designed primarily for industrial tracking and wearable applications, and are used in every day life and everywhere: in our pockets, our toys, our smart devices, our infrastructure, and our factories.

New generation low-cost receivers, boost GNSS receiver performance. Therefore, they have brought scalable and affordable high precision positioning – down to the decimeter-level – to the mass market and also have greatly improved the timing accuracies, using a new generation of multi-constellation, multi-band and high accuracy GNSS receivers. The addition of Galileo and BeiDou to GPS and GLONASS not only extends GNSS positioning to more obstructed environments, but also allows the use of new era.

In particular, a single most important trend that emerges from manufacturers’ responses is the improvement in receiver performance due to the increase in the number of satellites (now >120) and signals (now more than 100). Multi-constellation receivers are quickly becoming the norm, even in consumer devices. Over the next years, new GNSS services will become available and as the GNSS constellations continue to improve, the availability, reliability and repeatability of their signals will improve further. Αn also, continuing trend is the increasing threat from intentional and unintentional jamming and interference across the globe. Therefore, manufacturers continue to improve hardware and software techniques to defeat, or at least mitigate, this threat, greatly assisted by the increase in the number of available signals.

In the sustAGE project, outdoor positioning is based on the GNSS receivers built in smartphones. Combining this information with the 3D position and orientation of a quay crane spreader that is obtained via visual tracking, sustAGE is able to determine whether safe clearance distances from the moving spreader are maintained by all workers.

The initial estimated positional accuracy is at the level of a few meters. To improve positional accuracy, sustAGE uses differential corrections provided via Internet using the NTRIP protocol which uses the open Internet for the real-time collection and exchange of GNSS data, as well as for broadcasting.

Many manufactures like Google, Huawei and Samsung, build smartphones that access raw GNSS measurements and use different GNSS chipsets, thus result in different performance of measurements and navigation.

Since 2016, Google has publicly released GNSS Analysis Tools and applications to process and analyze GNSS raw measurements from Android mobile phones. For the sustAGE pilot use cases, workers used previous versions of mobile phones that are supported. More details are available in Deliverable 3.3 of the project that describes how multi-source localization is accomplished.

Newer mobile phones have upgraded chipsets, which use raw measurements to generate corrections to the errors caused by reflected GNSS signals, and thus perform with greater accuracy. Almost everyone has experienced this when using GNSS in cities, particularly when walking. If the phone has Galileo E5 (chipset) the accuracy improvements will be greater.

The rapid developments in mass-market segments are being utilized by new entrants especially within drones are challenging the traditional approach that requires certification to support safety-critical applications. It’s difficult to know precisely what the future will bring. But, it’s probably safe to say that satellite-based positioning still has plenty of surprises in store for all of us.

  1. S. Verhagen, D. Odijk, P. J. G. Teunissen and L. Huisman, “Performance improvement with low-cost multi-GNSS receivers,” 2010 5th ESA Workshop on Satellite Navigation Technologies and European Workshop on GNSS Signals and Signal Processing (NAVITEC), Noordwijk, Netherlands, 2010, pp. 1-8, doi: 10.1109/NAVITEC.2010.5708015.
  2. Xue, C., Psimoulis, P., Zhang, Q. et al. Analysis of the performance of closely spaced low-cost multi-GNSS receivers. Appl Geomat (2021). https://doi.org/10.1007/s12518-021-00361-8