GNSS is a term used for describing Satellite Navigation Systems that provide geo-spatial data and positioning with global coverage. GNSS and Global Positioning Systems (GPS) have made a big impact not only on Geographic Information Systems (GIS), but also on transportation, military equipment, mobile phones and other applications by providing high accuracy positioning and navigational functionality. GNSS allows GPS receivers to determine their exact location (geographical longitude, latitude and altitude) with a precision of a few meters using extremely precise time signals that are obtained with an atom clock and transmitted by radio from the satellites. GPS receivers calculate the time and positioning data and as a result they provide us with information about our position, speed, distance travelled, etc. The global coverage is usually achieved by a constellation of 20 to 30 satellites that are spread between several orbital planes, about 20,000 km from the Earth’s surface. [1, 2]
Nowadays the United States NAVSTAR GPS is the only fully operational GNSS available for people. However, there are more ones that are being restored or created and will be fully available in the years to come. For example, the Russian GLONASS that is currently not running at full capability, but is being restored to full operation. …
