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+# This program code is solely for study and communication purposes #
+
+# Main function introduction：
+
+1.Reads the specified observation data and navigation data.
+2.Calculate and document the longitude and latitude coordinates and height of the satellite at each epoch time.
+3.With the help of PyGMT, the output document information is processed and the satellite ground track map is drawn.
+4.With the help of MatLab tool, the satellite position is calculated and the station position is obtained by simultaneous solution, 
+  and the precision is evaluated by comparing with the coordinates of the precise station.
+
+# MAIN NOTICE
+
+## program notice
+  ### about main calculate
+  1.Due to the lack of program writing experience, 
+    the ease of file reading is not perfect, 
+    if you need to read other observation files and navigation files, 
+    you can make changes in the main.c file.
+  ### about PyGMT
+  1.I have improved the drawing part of PyGMT 
+    to ensure that the output data can be used independently.
+  ### about Matlab
+  1.When the new station data is needed for calculation, 
+    two parts of parameters in the Matlab source file need to be corrected, 
+    the first is the exact coordinates of the station in the file header, 
+    and the second is the longitude, latitude and elevation information of the station in the file header
+
+## Project notice
+1.Due to my limited programming level, PyGMT drawing used too miscellaneous judgment statements, 
+  resulting in slow drawing or debugging errors, please forgive me.
+2.When writing the code, with the help of the existing open source code results, 
+  and different degrees of reference, here one by one mark and express thanks:
+  
+  ||****|| https://blog.csdn.net/why1472587?type=blog               ||****||
+  ||****|| https://zhuanlan.zhihu.com/p/416072448                   ||****||
+  ||****|| https://www.pygmt.org/latest/index.html                  ||****||
+  ||****|| https://blog.csdn.net/FrankXCR/article/details/135438701 ||****||