Small batteryless wireless solar powered GPS receivers for subcentimeter land deformation monitoring

We design, implement, and validate a unique permanently deployed land deformation monitoring system using small (brick sized), cheap (approximately $100 USD), batteryless, solar powered singleband GPS wireless sensor nodes. Both hardware and software were designed, implemented, and validated by us. Constraints by our hardware and application prompted us to design a unique distributed relative static positioning algorithm designed for intermittent poor quality phase observable measurements, for sites with high multipath and high node densities requiring good solution accuracies; the static solutions were calculated on a daily basis. Our algorithm used a quarter of the bandwidth that would typically be required for an RF link used for a comparable application. GPS on time was observed to vary greatly from as little as 0.5 hours a day in winter to over 8 hours a day and summer in one of our tests. Typical solution precision was 4 mm 2DRMS. Simulations predicted an undesirable slowly changing solution bias that would repeat every year.