satellite-position-calculation-mapping

The subject of the study is to conduct research on the BeiDou satellite systems developed by China and to calculate the positions of the satellites. In this study, satellite positions were calculated using BeiDou-specific formulation with data received from BeiDou satellites, and then visualized on a world map with latitude, longitude, and altitude information.

The study concluded that some satellite data belonging to BeiDou (obtained from NASA) are partially faulty and need to be revised for successful satellite position results. Additionally, it was found that satellite position calculation varies depending on the types of orbits (GEO-MEO-IGSO) in which the satellites are placed. These conclusions were inferred after examining various articles, documents, and writings related to BeiDou satellite systems, and the accuracy of satellite positions was verified and confirmed through online testing.

Important details distinguishing BeiDou from other constellations were identified. Despite the lack of a clear solution method in articles and documents, an individually developed idea and solution method to overcome the problem were tested and finalized in this study.

Demo

Demo : Satellite Movements

satellite-movements.mp4

Demo : Satellite Label Detail

satellite-labelling.mp4

File Hierarchy

• /code : The codes developed during the project are located in this folder. Information on how to run the codes and their dependencies can be found in the About the Codes section.
• /datasets : The datasets created and obtained during the internship are available in this folder. Information on how the datasets were created, what they contain, and how they should be used is explained under the datasets title.
• /etc : Important resources related to the internship are shared here.

About the Codes

The creation of the codes prioritizes the use of a class structure and modularity. If we list the MATLAB(.m) files included in the project;

1. computeposition.m
2. keplerEq.m
3. main.m
4. R_matrix.m
5. read_BeiDou_Constellation.m
6. read_files.m
7. readRinexNav.m

If we list the text document (.txt) files within the scope of the project;

1. files_name.txt
2. BeiDouConstellationStatus.txt

If we list the image (.png) files within the scope of the project;

1. satellite.png

About Ephemeris and Rinex Parameters

I used these parameters for calculating the BeiDou satellite position from Rinex and Ephemeris data.

Working Method

SUMMARY: The person who wants to run the project can confirm the correctness of parts 1. and 2. without reading the lines below and run the project using the data available in the project [the project should run from the main]. If it is desired to display in real-time or at a standstill, the comment lines in the code can be followed. During the visualization of the project, other information of the satellite can be displayed by clicking on the satellites with the mouse. If there are other RINEX data for BeiDou and it is desired to try them, the steps below can be followed to ensure the whole process can be carried out in a comprehensible way.

The project is managed through the main.m file and other files are being called. First, some configurations need to be made within the main.m file. These are;

1. In the code line 1. [data_name] = read_files(" "), the name of the files_name.txt file located in the current /code folder should be written. Any text file can also be added here. The purpose of this text file should be to list all the names of the files in the folder where the rinex files are kept. For example, location information such as "datasets/ASCG00SHN_R_20210250000_15M_CN.rnx should be entered. The reason for this is related to the cessation of visualization and data acquisition studies within the scope of the project, and the current project draft is found sufficient.

2. Next, in the same file, in the "index_of_data=1:number of satellite" loop beginning, a value as many as the number of data read in the [data_name] part should be entered. Files will be read and calculated up to this number.

3. The [datas] = readRinexNav(data_name(index_of_data)) section sends the information of the file it reads in the folder where the RINEX files are to the readRinexNav.m file, and the calculated value is returned to the [datas] array.

4. In the readRinexNav.m file, the received data is read iteratively. It performs the reading and parsing of ephemeris data by removing errors specific to BeiDou. The relevant data is stored in the beidouEphemeris variable in the order in the RINEX format and sent back to the main.m file.

5. The format of the sent (datas) file is in struct format and the data inside can be accessed as datas.beidouEphemeris and this file is saved to the beidou_datas variable.

6. In the computeposition computeposition (beidou_datas) section, the parameters sent are processed in computeposition.m and perform position calculation. The returned values are 6 in total. These are;

• Longitude
• Latitude
• Altitude
• name
• exec
• Satellitesinfo

are stored in variables. In this part, the prepared Kepler equation is used for the calculation, the keplerEq.m file with the Kepler equation is run. The returned values are used in the calculation sections.

7. In the read_BeiDou_Constellation("BeiDouConstellationStatus.txt") section, the position of the BeiDouConstellationStatus.txt text document is written exactly and sent to enter the read_BeiDou_Constellation.m file. All known constellation information of BeiDou in this file is read and stored in the [Beidou_Constellation] variable.

8. The parameters in the "iconDir" and "iconFilename" sections should remain constant, can be changed as desired. "iconDir" shows the location of the current satellite icon. "iconFilename" names the existing satellite.png file and its location by combining the full file name with the fullfile function.

9. The subsequent code blocks execute the visualization process embedded in the main.m It does this through the Web Map Display plugin in MATLAB. This plugin must be installed. Displaying satellite positions on the label, revealing their information is accomplished through the webmap function.

About Datasets

Data from the NASA Earth Data platform providing data for BeiDou throughout the project has been used. These data were tried in the years 2020-2021 and the xxf file was selected. The f value here is the code of the data provided for BeiDou satellites. The reason for preferring this platform was that BeiDou navigation data could not be obtained from another source. Only this platform was used as a source within the scope of the project. However, it is stated that the data here will give more reliable results by resolving the BeiDou satellite information packages over UBlox. Sample datasets are located in the /datasets folder. The data here can be used for testing purposes. The data are in RINEX 3.04 - 3.03 format, and operations were carried out according to the data order and guidelines specified in the RINEX Documentation. The project reads and processes files in the RINEX dataset format. Files to be used as a dataset should be in this format

About the Report

The report of the project is located in the/docs folder. The report, which is quite comprehensive and presents all the details, is explained step by step in an easy-to-understand format. Besides the report, there are explanatory lines in all code lines, making it easier for the person reading the code.

Other Important Points

In the project, the results of the GEO satellites in the satellite position calculation cannot be calculated as a result of the data obtained from NASA Earth Data. The reason for this is explained in detail in the related report file. It can be said that the project has been examined in detail in many different areas, not only satellite position calculation, but also the arrangement of RINEX data, visualization process, differences in the orbital constellation calculations of BeiDou. For all possible information about this, you can reach our report under /docs.