Program Description 
The main implementation part consists of a program named “CityGML2IFC.py” it is a script file written in Python 3. 
When compiled the program will convert a source file in CityGML to a destination file in IFC.
License 
and the program is licensed under General Public License v3.0

Participation 
It is made with the help of Kavisha Kumar https://3d.bk.tudelft.nl/kavisha/.  
Kavisha’s GitHub  https://github.com/kkimmy. 

Used Moules 
The following modules are imported and used in the program; these modules should be preinstalled before running the program: 
xml.etree.ElementTree    _ Is used here for parsing the XML data 
os _    To interact with the operating system where the computer is running for example: reading time and file bath. 
time_ To read the current time and stored in the created IFC files
itertools _     Is used to create a hashtaged unique id with an incremental value starting from a given value
sys    _ Is used to allow files to be written on the hard disk 
numpy _    To perform mathematical operation such as finding minimum value or subtract arrays 
uuid_ To automatically generate unique IDs 
pyproj _    To convert the resulting files projection 

How to use program
1-    Make sure that python 3 is installed. 
2-    Make sure all the necessary modules are installed, particularly: 
a.    numpy 
b.    pyproj 
3-    Download the program CityGML2IFC.py
4-    the program will convert a source file in CityGML to destination file in IFC. 
5-    Change the name of your source CityGML file to: “Source.gml”  
6-    Compile (Run) the program CityGML2IFC.py. 
7-    A file called Result.ifc will appear. This file is the result of the conversion. 
8-    Check Result.ifc on the BIM software of your choice.