Coordinate Systems Today we cover: Definition of coordinates - Conventionalrealization of coordinates Modern realizations using spaced based geodetic systems (such as GPS)
Potential field based coordinates: -Astronomical latitude and longitude -Orthometric heights (heights measured about an equipotential surface, nominally mean-sea-level
GPS Observables Today's class we start discussing the nature of GPS observables and the methods used to make range and phase measurements Start with idea of remotely measuring distances
Examined methods for measuring distances Examined GPS codes that allow a type of distance measurement and phase to be measured Examine how the range measurements are defined Use of carrier phase measurements Examine rinEx format and look at some \raw data
Basic concepts Basic problem: We measure range and phase data that are related to the positions of the ground receiver, satellites and other quantities How do we determine the \ best position for the receiver and other quantities What do we mean by best \ estimate?
Estimation · Summary Examine correlations -Process noise · White noise · Random walk First-order Gauss Markov Processes Kalman filters Estimation in which the parameters to be estimated are changing with time
Propagation Basics: - Signal, tagged with time from satellite clock, transmitted. - About66msec(20,000km) later the signal arrives at GPS receiver. Satellite has moved about 66 m during the time it takes signal to propagate to receiver
Propagation: lonospheric delay Summary -Quick review/introduction to propagating waves -Effects of low density plasma Additional effects -Treatment of ionospheric delay in GPS processing -Examples of some results
Mathematical models in GPS Review assignment dates (updated on class web page) Paper draft due Mon April 29 Homework 3 due Fri May 03 -Final class is Wed May 15. Oral presentations o papers. Each presentation should be 15-20 minutes, with additional time for questions. · Next three lectures:
