Given:

• Time (GPS week, seconds of the week) and XYZ coordinates (meters) for PRN 24 (text file) ,
• TMGO RINEX Data
• ReadObsHeader.m
• ReadObsRecord.m
• parsef.m
• GPS_week.m
• Gps_to_sec.m

Comments:

As long as it was working, it is a good idea to start with last week's homework. All questions in this lab refer to PRN 24. For this lab, R_L1 means C1 and R_L2 means P2.

Your code should be set up to read the RINEX header, and then to read as many RINEX obervation records as needed. If you want to read to the end of the file, use feof, i.e. set up a while loop, while ~feof(fid).

The orbit time-tags are defined in GPS week and GPS second of the week, the timing system used by the DoD. RINEX files were created by scientists (primarily geodesists) and they wanted something more normal, like year, month, day, hour, minute, second. The function GPS_week allows you to to calculate the week/second of the week from Y/M/D HH:MM:SS. Gps_to_sec.m is used to convert from seconds of the week to seconds since midnite.

Goal: to see how a GPS data file relates to the observable equations we are learning about in class.

Lab instructions:

1. Define GPS constants.

2. Assign file ID. Check to see if there is an error.

3. Read the RINEX header of the given file.

4. Convert the receiver coordinates into latitude, longitude, and height. Print to screen.

5. Determine the location of C1, P1, P2, L1, L2.

6. Load the file of satellite coordinates (you can also use file ID, etc, but since the data are in columns, it is easier to use load).

7. For the times in the satellite coordinate file:
   • Calculate elevation angle; plot (time in hours past midnite; elevation angle in degrees).

   • Calculate geometric range (GR) as a function of time; plot (time in hours past midnite; GR in km).

8. Read in the observations from your RINEX file for PRN 24.

9. Plot R_L1 - GR (meters). Describe the errors in the plot. Speculate as to which error source is responsible for the mean value on the y-axis.

10. Plot R_L1 - R_L2 data. Describe the errors in the plot.

Turn in: code, answers to questions, and plots. x-axis limits should all be in hours since midnite.