C:\exc99\GEOD98e.EX8.wpd

Geofysisk Afdeling, Juliane Maries Vej 30, 2201 København Ø.

Geodæsikurset, Exercise 8.

The purpose of the exercise is to show how the program QUICKPLAN can be used to obtain a survey over number of satellites, directions to and heigh angle of the GPS satellites.

The program QUICKPLAN can be run on the PC in the GPS-room or on the portable PC. Windows is used. Click on GPSurvey ,and then on QUICKPLAN. The programme is menu-driven. Use the HELP-functions to guide you in the programme.

(1) Use the point in Buddinge for the survey. If it is in the list of stations, click on "keyboard" and then type Buddinge.
(2) Make a survey of (by clicking on Graph) of
Visible satellites
Number of satellites
PDOP, HDOP
(3) Make a skyplot.
(4) Change the date to the following week and repeat (2), (3)
with the date one week later. Note how much or how little the picture have changed.

In the following exercises Torge, Section 4.4 is used.

(5) The GPS satellites are supposed to have a circular orbit with centre in the gravity centre of the Earth and radius 26000 km. What is the revolution time ? (You may use Quickplan to find this out but the Kepler laws must be used).

(6) A GPS satellite is located exactly above a point with latitude and longitude both 0 degrees. Where is the satellite after exactly two revolutions ? (The orbit inclination is supposed to be 90 degrees).

(7) A satellite has a=7000000 m, e=0.001, M=45o, OMEGA = 60o, omega = 60o and i = 80o at a time which in siderial time is 45o=6 hours.

Compute first (iteratively) the excentric anomaly E. Then the "Latitude" v in the orbit plane.

What is the position of the satellite (X,Y,Z) in Cartesian coordinates expressed in geocentric latitude, longitude and distance r from the Earth centre in an inertialcoordinatesystem. What is the longitude in a coordinate system fixed with respect to the Earth ?

What is the geographic latitude for the satellite in the GRS80 = WGS84 coordinate system ?

Last update 1999-05-13 by cct.