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Global Navigation Satellite Systems (GNSS) are satellite-based positioning systems that permit users to establish precise positions on the surface of the Earth. MGI uses two GNSS systems, often simultaneously, for our land surveying operations:
- The Global Positioning System (GPS) was established by the US Department of Defence and includes 32 functioning NavStar satellites, ensuring that at least four satellites are visible from anywhere on the Earth at a given time. The control segment, with five tracking stations distributed around the Earth, provides continuous upgrade of satellite orbital information (ephemerides) and monitors the “health” of the satellites.
- GLONASS was developed by the Russian government and includes 24 satellites. This constellation significantly enhances positioning capability in northern latitudes and in tree cover.
Radio wave signals from GNSS satellites are continually transmitted on two carrier frequencies. GNSS receivers record carrier data, "pseudorange" measurements, and other information, enabling a GNSS operator to compute the positions in space of the satellite and the GNSS receiver. Using both carrier frequencies enables the operator to correct for ionospheric distortion to achieve metre-level positioning accuracy. Differential GNSS uses simultaneous signals from several satellites at two or more unique GNSS receiver positions to provide centimetre-level positioning accuracy.
MGI implemented MACS (MGI Active GNSS Control System) for its northwestern Alberta surveys in 2004. We use static, rapid static, and real-time kinematic (RTK) in applying GNSS technologies to a variety of geo-spatial projects, including:
- cadastral surveys
- engineering surveys
- geo-referencing
- positioning infrastructure
- continuous feature modelling
- automated vehicle-tracking
- navigation
- airborne mapping control
- global change studies
- geodynamics
We also use GNSS technologies—including design, establishment, analysis, and adjustment—to create a seamless global spatial reference frame for a variety of control surveys, including:
- geodetic control
- project-related control networks
- active GNSS control
- photogrammetric control
- high-precision networks
