Network Development of Network First measurements made in July 1992; just after start of International GPS Serviceigs). Since then measurements each year and often multiple campaigns per year. -The current network has over 1000 sites, many of them being recovery marks for the main
GPS Groups/Gs There are many international and national groups involved in the deployment of GPS The international organization is the International GPs Service(IGs)
Rank deficiencies Ranks deficiencies are combinations of parameters that can not be separately estimated In GPs. there are several rank deficiencies UTl, Longitudes of all the stations and the nodes of the satellite orbits, effectively can not be separated In theory, orbit perturbations by the moon/sun on the GPs
Basic antenna operation Receiving and transmitting antennas are identical: Time just flows in opposite directions. Antenna problems are solved knowing the current distribution J(x') in the antenna and using a vector potential