The　development　of　low-cost　GNSS　receivers　broadens　their　applications,　such　as　deformation　monitoring,　which　have　been　performed　routinely　by　survey-grade　GNSS　receivers.　To　evaluate　the　performance　of　low-cost　GNSS　receivers,　we　assessed　the　precision　of　low-cost　multi-GNSS　receivers　in　monitoring　dynamic　motion　and　developed　methods　of　using　a　closely-spaced　dual　low-cost　GNSS　receivers＇　system　to　enhance　their　performance.　In　this　study,　both　the　survey-grade　and　low-cost　GNSS　receiver/antennas　were　mounted　on　a　circular　rotating　device　executing　controlled　periodic　rotation.　It　was　shown　that　the　precision　of　the　low-cost　GNSS　receivers　could　be　enhanced　to　the　level　of　2-4　mm,　by　using　multi-GNSS　observations　and　limiting　the　noise　level　based　on　error　modelling　and　filtering　of　the　closely-spaced　low-cost　GNSS　receivers.　Finally,　from　the　experiments　and　a　real　bridge　monitoring　application,　it　was　proved　that　low-cost　GNSS　receivers　could　accurately　define　modal　frequencies　of-0.362　Hz　and-1.680　Hz,　respectively.