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

Basic atmospheric structure mosphere Troposphere is 2 100 where the temperature stops decreasing in the tmosphere(10 km altitude)

Specific common processes White-noise: Autocorrelation is Dirac-delta function; PSD is flat; integral of power under PSD is variance of process(true in general) First-order Gauss-Markov process (one of most models common in Kalman filtering)

Statistical approach to estimation Examine the multivariate Gaussian distribution: (x-)\v-(x-) Multivariant f(x)= Minimize (x-u)'v(x-u) gives largest probability density By minimizing the argument of the exponential in the probability density function, we maximize the likelihood of the estimates(MLE)

Summary · Review: -Examined definitions of pseudorange and carrier phase Looked at some actual raw measurements from a RINEX file Today we look at:

Today's Lecture Examine specifics of GPS signals Multiple modulations on same carrier signal Structure of signals GPS receiver operation and satellite acquistion

Treat the basic description and dynamics of satellite orbits Major perturbations on GPS satellite orbits · Sources of orbit information: -SP3 format from the International GPS service Broadcast ephemeris message