Raymond Raymond / Python Programming

Geoanalytics with geopandas and ABS Public Data in Python

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Geoanalytics with geopandas and ABS Public Data in Python

Geoanalytics is a powerful field that combines geographic location with data analysis. It provides a visual perspective, uncovers hidden insights, and enhances decision-making by integrating geography with data analysis. This article shows you how to use Python package geopandas to analyze and visualize ABS (Australian Bureau of Statistics) published public data.

About geopandas

Python package geopandas is an open-source Python library that extends the capabilities of pandas (a popular data science library) to handle geospatial data. It builds on top of pandas and shapely. It allows you to work with both tabular data (like pandas DataFrames) and geometries (such as points, lines, and polygons). There are several key components in this library:

  • GeoDataFrame: A GeoPandas GeoDataFrame is a subclass of pandas DataFrame that can store geometry columns and perform spatial operations.

  • GeoSeries: A GeoSeries is a subclass of pandas Series that handles geometries.

  • You can have multiple columns with geometries in a GeoDataFrame, each potentially in a different coordinate reference system (CRS).

For easily data analytics, I recommend you to use a notebook environment to run the Python code, for example, Jupyter Notebook.

Install the package

Run the following command to install required Python packages into your environment:

pip install geopandas
pip install matplotlib

Note - matplotlib will be required to plotting in this tutorial.

Download ABS SA4 digital boundary data

ABS publishes different levels of digital boundary data as part of Australian Statistical Geography Standard (ASGS) Edition 3.  You can download them from this official page. ABS provides different levels of digital boundary data as the following image shows:

2024040690006-image.png

*Image from Australian Statistical Geography Standard (ASGS) Edition 3, July 2021 - June 2026 | Australian Bureau of Statistics (abs.gov.au).


We will use data set Statistical Areas Level 1 - 2021 - Shapefile.

Extract the data

After downloading the zip file, extract it into a folder. I am extracting it to a subfolder named data:

Mode LastWriteTime Length Name

---- ------------- ------ ----

-ar--- 20/04/2021 8:31 AM 39272153 SA1_2021_AUST_GDA2020.dbf

-ar--- 20/04/2021 8:31 AM 160 SA1_2021_AUST_GDA2020.prj

-ar--- 20/04/2021 8:31 AM 153904384 SA1_2021_AUST_GDA2020.shp

-ar--- 20/04/2021 8:31 AM 494860 SA1_2021_AUST_GDA2020.shx

-a---- 21/06/2021 8:01 AM 25585 SA1_2021_AUST_GDA2020.xml

It contains several files that will be used later.

Read shapefile to GeoDateFrame

The above published dataset is in format of shapefile. We can use geopandas to read it directly.

import geopandas as gpd
shp_file_path = 'data/SA1_2021_AUST_GDA2020.shp'
data = gpd.read_file(shp_file_path)

The related attributes information in file *.dbf will also be read.

Explore the data

We can use the common pandas DataFrame methods to explore the data.

data.columns

The above code prints out the following column list information of the DataFrame:

Index(['SA1_CODE21', 'CHG_FLAG21', 'CHG_LBL21', 'SA2_CODE21', 'SA2_NAME21', 'SA3_CODE21', 'SA3_NAME21', 'SA4_CODE21', 'SA4_NAME21', 'GCC_CODE21', 'GCC_NAME21', 'STE_CODE21', 'STE_NAME21', 'AUS_CODE21', 'AUS_NAME21', 'AREASQKM21', 'LOCI_URI21', 'geometry'], dtype='object')

The last column geometry is in format of WKT.

print(data.loc[0, 'geometry'])

The following is the WKT extract from the first geometry.

POLYGON ((149.8911094722651 -35.0898882056091, 149.89181447220685 -35.08951620566876, 149.8924794621867 -35.0888981957232,...-35.09042220555832, 149.89074246229112 -35.090115205578286, 149.8911094722651 -35.0898882056091))

The numbers are coordinates of SA1 10102100702.

data.shape

The above line will print out the following information:

(61845, 18)

It means there are 61845 geometries in this data set at SA1 level across Australia.

data.iloc[1]

The above code prints out the attributes (columns) of the first row in the DataFrame:

SA1_CODE21 10102100702

CHG_FLAG21 0

CHG_LBL21 No change

SA2_CODE21 101021007

SA2_NAME21 Braidwood

SA3_CODE21 10102

SA3_NAME21 Queanbeyan

SA4_CODE21 101

SA4_NAME21 Capital Region

GCC_CODE21 1RNSW

GCC_NAME21 Rest of NSW

STE_CODE21 1

STE_NAME21 New South Wales

AUS_CODE21 AUS

AUS_NAME21 Australia

AREASQKM21 229.7459

LOCI_URI21 http://linked.data.gov.au/dataset/asgsed3/SA1/...

geometry POLYGON ((149.73421044994282 -35.3675691937016...

Name: 1, dtype: object

This give you a hint about what the data looks like.

data[data['STE_NAME21'] == "Victoria"]['SA4_NAME21'].unique()

The above code prints out the SA4 list in state Victoria:

array(['Ballarat', 'Bendigo', 'Geelong', 'Hume', 'Latrobe - Gippsland', 'Melbourne - Inner', 'Melbourne - Inner East', 'Melbourne - Inner South', 'Melbourne - North East', 'Melbourne - North West', 'Melbourne - Outer East', 'Melbourne - South East', 'Melbourne - West', 'Mornington Peninsula', 'North West', 'Shepparton', 'Warrnambool and South West', 'Migratory - Offshore - Shipping (Vic.)', 'No usual address (Vic.)'], dtype=object)

Convert WKT to geojson

geopandas provides built-in function that can be used to save the DataFrame to geojson file. The following is an example:

shp_file_path = 'data/SA1_2021_AUST_GDA2020.shp'    
geojson_file_path = 'data/SA1_2021_AUST_GDA2020.geojson'
data = gpd.read_file(shp_file_path)
data.to_file(geojson_file_path, driver='GeoJSON')

The driver='GeoJSON' argument ensures that the output file format is GeoJSON. 

If you just want to convert a single WKT string to GeoJSON format, you can shapely directly:

from shapely.geometry import mapping
# Convert the geometry to GeoJSON
geojson = mapping(data.loc[0, 'geometry'])
print(geojson)

The output looks like the following:

{'type': 'Polygon', 'coordinates': (((149.8911094722651, -35.0898882056091), .... }

Plot examples

Now let's start to plot the GeoDataFrame. Similarly as pandas DataFrame, we can directly plot with built in methods.

Plot the whole DataFrame

data.plot()

The output looks like the following screenshot:

2024040684734-image.png

Plot the first 10 geometries

data.head(10).plot()

The output:

2024040684831-image.png

Plot Victoria state

data[data['STE_NAME21'] == "Victoria"].plot()

The above code filters on state name and then plot all the geometries in Victoria state. The output looks like the following screenshot:

2024040684952-image.png

Plot Greater Melbourne area

print(data[data['GCC_NAME21'] == "Greater Melbourne"]['SA4_NAME21'].unique())
greater_melbourne = data[data['GCC_NAME21'] == "Greater Melbourne"]
greater_melbourne.plot()

The output looks like the following:

['Melbourne - Inner' 'Melbourne - Inner East' 'Melbourne - Inner South' 'Melbourne - North East' 'Melbourne - North West' 'Melbourne - Outer East' 'Melbourne - South East' 'Melbourne - West' 'Mornington Peninsula']

2024040685405-image.png

Dissolve from SA1 to SA4 level

For SA4 level data, there are in total 61845 geometries and the map looks very busy. We can use dissolve method to create higher level maps directly.

Note - You can also read from SA4 digital boundary file directly to plot.

The following code snippet dissolve by column SA4_NAME21. It also adds labels to the center of the geometry.

import matplotlib.pyplot as plt

# Create a new figure with a specific size (width, height)
fig, ax = plt.subplots(figsize=(15, 10))

# Dissolve the data by 'SA4_NAME21' and plot it
dissolved = greater_melbourne.dissolve(by='SA4_NAME21')
dissolved.plot(ax=ax)

# Add labels
for x, y, label in zip(dissolved.geometry.centroid.x, dissolved.geometry.centroid.y, dissolved.index):
    plt.text(x, y, label)

plt.show()

The output looks like the following screenshot:

2024040685748-image.png

Plot with data metrics

It doesn't provide any insights directly if we just plot with geometries. Now let's add some data metrics to visualize on the map. We will use another ABS dataset of population from Census 2021.

Download the census data

Go to page Census DataPacks | Australian Bureau of Statistics (abs.gov.au). Select SA4 as the following screenshot shows:

2024040690255-image.png

Download the Victoria data from this link: https://www.abs.gov.au/census/find-census-data/datapacks/download/2021_GCP_SA4_for_VIC_short-header.zip.

Extract the data to a directory. I'm saving the data to a directory named '2021_GCP_SA4_for_VIC_short-header' in my project folder.

The folder contains a number of CSV files:

2024040690457-image.png

Read the census data as DataFrame

Now we can easily read the data as DataFrame using pandas:

# Read population data from ABS SA4 level
import pandas as pd
import glob

# Get a list of all CSV files in the directory
csv_files = glob.glob('2021_GCP_SA4_for_VIC_short-header/2021 Census GCP Statistical Area 4 for VIC/*.csv')

# Read each CSV file into a DataFrame and store them in a list
dfs = [pd.read_csv(f) for f in csv_files]

# Concatenate all dataframes in the list into a single DataFrame
df_census = pd.concat(dfs, ignore_index=True)
df_census.shape

The output:

(2261, 16294)

There are 2261 records in the DataFrame object. Let's further explore the dataset using the following code:

df_census.columns

It prints out the following:

Index(['SA4_CODE_2021', 'Tot_P_M', 'Tot_P_F', 'Tot_P_P', 'Age_0_4_yr_M', 'Age_0_4_yr_F', 'Age_0_4_yr_P', 'Age_5_14_yr_M', 'Age_5_14_yr_F', 'Age_5_14_yr_P', ... 'Three_meth_Tot_three_meth_P', 'Worked_home_M', 'Worked_home_F', 'Worked_home_P', 'Did_not_go_to_work_M', 'Did_not_go_to_work_F', 'Did_not_go_to_work_P', 'Method_travel_to_work_ns_M', 'Method_travel_to_work_ns_F', 'Method_travel_to_work_ns_P'], dtype='object', length=16294)

We will primarily use column SA4_CODE_2021 and Tot_P_P which represents SA4 code and total population accordingly.

df_census['SA4_CODE_2021']=df_census['SA4_CODE_2021'].astype(str)
df_census_subset = df_census[['SA4_CODE_2021', 'Tot_P_P']]

The above code snippet creates a subset and also convert column to SA4_CODE_2021 to object type so that we can join with our GeoDataFrame later.

Join the two DataFrames

greater_melbourne2 = greater_melbourne.merge(df_census_subset, left_on='SA4_CODE21', right_on='SA4_CODE_2021', how='left')
greater_melbourne2 = greater_melbourne2.dropna()

The above code snippets joins the two dataset by column SA4_CODE21 and SA4_CODE_2021.

Plot the population metric

Now let's plot the populations of each SA4 area of Greater Melbourne region on a map:

import matplotlib.pyplot as plt

# Create a new figure with a specific size (width, height)
fig, ax = plt.subplots(figsize=(20, 10))

dissolved2 = greater_melbourne2.dissolve(by='SA4_NAME21')
dissolved2.plot(column='Tot_P_P', legend=True, ax=ax, cmap='YlGn')

# Add labels
for x, y, label in zip(dissolved2.geometry.centroid.x, dissolved2.geometry.centroid.y, dissolved2.index):
    plt.text(x, y, label)

plt.show()

It outputs the following chart:

2024040691358-image.png


Summary

As you can see, it is very easy and flexible to plot this the public Geo data. Have fun with GeoAnalytics! 

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