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=45^{o}, OMEGA = 60^{o}, omega =
60^{o} and i = 80^{o} at a time which in siderial time is 45^{o}=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.