CityGML-CityJSON

Practice of citygml-tools and cjio.

• Convert the CityGML file into CityJSON with citygml-tools.
• Validate the CityJSON file with cjio command line. Upgrade the file and validate it.
• Python practice to retrieve data of buildings from the CityJSON file.

Project: Building Height Analysis from CityJSON Data

Overview

This project provides a Python script to analyze building height data from a CityJSON file. It generates a distribution of buildings based on their heights and visualizes the data in a pie chart. The script performs the following tasks:

• Loads a CityJSON file containing city object data.
• Extracts building height information.
• Categorizes buildings into height ranges.
• Creates a pie chart to visualize the distribution of building heights.

Requirements

• Libraries:

  os

  json

  pandas

  matplotlib

File Structure

• Vienna_102081_v20.city.json: The input CityJSON file containing city object data. It has been converted and upgraded from the CityGML file with citygml-tools and cjio command line.
• main.py: The main Python script that processes the CityJSON data, calculates height distributions, and generates a pie chart.

Functions

1. load_cj_file(file_path):

• Loads the CityJSON file from the specified path.
• Returns the parsed JSON data.

2. buildings_heights(cj):

• Extracts building and building part heights from the CityJSON data.
• Returns a dictionary of building IDs and their corresponding heights.

3. height_distribution(bd_heights):

• Categorizes the buildings based on their heights into 4 categories:

  '0-10m',

  '10-20m',

  '20-30m',

  '30m+'

• Returns a pandas DataFrame showing the distribution of buildings across these height categories.

4. pie_chart(hd):

• Generates a pie chart based on the height distribution.

• Displays the chart with labeled height categories and percentage of buildings in each category.

5. main(file_path):

• Integrates the above functions to process a CityJSON file, calculate building height distributions, and display a pie chart.