Global Navigational Satellite Systems (GNSS) are designed for determination of objects positions on the Earth surface. Two systems, namely GLONASS (RUSSIA) and NAVSTAR-GPS (USA) have become widely used at present.

In accordance with the SOLAS Convention Chapter 5 “ Navigation Safety” provisions the unconditional demand for all the ships, built before July 1, 2002 and to be built later is the additional installation on board of all the ships independently of their displacement receivers of GNSS or other Radio Navigational System operating in the area of navigation.

The NAVSTAR – GPS system allows to determine object’s position and speed practically in every place on Earth except for the polar areas. 24 GPS satellites moving at the height of 20180 km above the Earth are the basis of the system. The satellites are moving along 6 orbital trajectories, 4 satellites being at each trajectory.   The trajectories’ planes are extended at an angle of 55 degrees. The GPS satellites transmit special signals in 1575,42 MHz band.

The navigational signals transmitted by the satellites are received by GPS-receivers. These receivers determine object’s position by the method of received signals’ triangulation. Used by the civil marines the coarse acquisition (c/a) code allows determine position of an object with the accuracy up to 100 meters. Used by the United States Navy the “P” accurate code allows determine position of an object with the accuracy up to 20 meters.

The GLONASS as well as GPS system allows determine object’s position and speed practically in every place on Earth except for polar areas. 24 GPS satellites (number of satellites is reduced at present) moving at the height of 19130 km above the Earth are the basis of the system. The satellites are moving along 3 orbital trajectories. The trajectories’ planes are extended at an angle of 64,8 degrees. The GLONASS satellites transmit special signals within 1598,0625 - 1604,25 band.

The navigational signals transmitted by the satellites are received by GLONASS-receivers. These receivers determine object’s position by the method of received signals’ triangulation. Used by the civil marines the code allows determine position of an object with the accuracy up to 50 - 70 meters. In the mode of usual access the GLONASS system exceeds the GPS system in accuracy, at the same time providing opportunity for operation in areas of higher latitudes.

Due to insufficient observation accuracy necessary for navigation in narrow waters the IMO recommendations assume additional use of GPS and GLONASS differential subsystem. A special method in which the updating information from the land-based stations is used allows increase position’s accuracy up to 5-10 meters.

dKart Navigator и dKart Explorer electronic chart systems are able to work with GPS and GLONASS receivers as well as with receivers of related differential subsystems.