## 1 Introduction  
Currently, the use of GNSS positioning is a common practice because GPS/GNSS receivers are included in various instruments, such as smartphones and cars. Many types of receivers and antennas are available, depending on cost and application. Receivers range from geodetic triple frequency and multi-constellation (which currently cost over 5000 euros) to mass-market instruments that typically use only the GPS constellation and pseudorange measurements of at least the L1 (single frequency) GPS frequency, which costs a few hundred euros. Besides the cost, these receivers differ in positioning accuracy and precision; the first one allows us to obtain centimeter accuracy in real-time positioning (using Continuous Operating Reference Stations--CORSs) and a sub-centimeter accuracy in post-processing [1], after a network adjustment.  
The second class of receivers are (in theory) less precise compared to the first type and allow us to obtain an accuracy of a few meters in real-time stand-alone positioning and an handful of centimeters (_i.e._, four to six cm) in real-time if a CORSs network is considered [2]. Regarding post-processing, it is possible to obtain an accuracy of about two to five cm, if considering a Virtual Rinex: this is a data file of a virtual station generated by the network software that manages the CORSs network [3].  
The use of mass-market receivers is widespread, primarily thanks to their low cost. GPS chips are produced in millions of copies and costs only a few euros. Very often these receivers are assembled in 'evaluation kits' (composed of a receiver and a patch antenna) with a cost of about $200-300 and more often they are coupled with inertial sensors [4; 5; 6]. All these instruments are able to track the GPS signals, but a few of them are also able to track the GLONASS constellation [7; 8]. The goals of this research are to analyse and test the performance of this last type of receiver in order to understand whether a multi-constellation receiver is useful for mass-market applications (_i.e._, mobile mapping, navigation, precise farming, _etc._).  
Some of them are also able to manage differential corrections broadcasted by software that manages a CORSs network while others are only able to make a stand-alone positioning. In the first case, with this type of receiver, it is also possible to do a Network Real-Time Kinematic (NRTK) positioning [9]. Some are also able to store raw data (pseudorange, carrier-phase, and Doppler measurements) in their internal memory, while others need an external device to store data (_i.e._, a laptop), and still others are not able to save any raw data.  
Some tests were designed at the Politecnico di Torino in order to demonstrate the performance of mass-market receivers for various purposes (mobile mapping [10], precise farming, disaster management [11], surveying and mapping [12]) considering receivers able to track only the GPS constellation; the goal of this work is to analyse the performances of mass-market receivers that are able to track the GLONASS constellation [8; 13; 14] in order to demonstrate the benefits of multi-constellation receivers for mass-market instruments.