Crafting a Storm Surge and Hurricane Risk Rating for Coastal Properties

Crafting a Storm Surge and Hurricane Risk Rating for Coastal Properties

In an era where climate change is intensifying the frequency and severity of storms and hurricanes, especially in coastal regions, understanding and quantifying the associated risks is critical.

According to the National Geographic Society, a storm surge is a rise in sea level that occurs during tropical cyclones, which are intense storms also known as typhoons or hurricanes.

The storms produce strong winds that push the water into shore which can lead to flooding and pose a real threat in coastal regions.

To help understand these risks, a Storm Surge and Hurricane Risk Rating score can provide property owners, developers, real estate agents, insurers, urban planners, local governments, buyers and investors with a clear picture of a property’s vulnerability to these natural disasters.

These stakeholders will be conducting their own necessary research, and a risk rating system can offer an indicative metric to guide their decisions.

Why is a Storm Surge and Hurricane Risk Rating Important?

Understanding storm surge and hurricane risks is crucial for building a resilient society.

Natural catastrophes pose significant challenges, and quantifying these risks can aid in better preparation and prompt responses.

Strengthening homes and incentivising homeowners to invest in property fortification can reduce potential losses. Accurate risk assessments and reliable data can allow insurers to offer discounts for mitigation actions, enhance home resale values, and reveal the increased costs to mortgage issuers due to natural disasters.

Achieving resilience relies on expert understanding of the real estate ecosystem and the benefits of informed mitigation strategies.

Steps to build a Storm Surge and Hurricane Risk Rating

1. Defining scoring criteria and scale

The foundation of a risk rating system is a clear and understandable scale, such as 1 to 10, with each number representing a different level of risk.

Establishing specific criteria for assessment is also essential for a well-rounded evaluation.

2. Key factors to consider

Several factors contribute significantly to a property’s risk from storm surges and hurricanes:

Proximity to coast

 

  • Proximity to Coastline: The closer a property is to the coastline, the higher the risk of storm surge impacts.
  • Elevation and Topography: Properties at higher elevations or with certain topographical features may have reduced risk.
  • Historical Data: Analysing past hurricane and storm surge incidents from historical weather databases and local government records can provide critical insights into potential future risks.
  • Local Climate Trends: Understanding the local weather patterns can help predict the likelihood of storms.
Natural barriers
  • Flood Zone Designation: Properties in designated flood zones face a heightened risk. Flood risk information is generally available from Local Councils.
  • Building Design and Materials: Construction that is designed to be resilient against high winds and flooding can mitigate risk.
  • Infrastructure and Preparedness: Robust local infrastructure and emergency plans can play a vital role in risk reduction.
  • Natural Barriers: The presence of natural features, such as dunes or wetlands that can absorb storm impacts, reduces risk.
  • Regional Planning: Effective community and regional planning and zoning can mitigate potential damage. Consult local zoning laws and development plans for more property-specific.

3. Assigning weights to each factor

Assigning appropriate weights to each of the above factors based on its impact on overall risk ensures that the score accurately reflects the property’s vulnerability.

Use expert consultations and statistical analysis to determine appropriate weights, and adjust weights based on real-world data and expert feedback.

4. Data collection and analysis

Gathering and analysing data, including GIS mapping, climate records and historical event data, is crucial to assigning accurate sub-scores for each criterion. Cross-referencing multiple sources will ensure data accuracy and statistical software can be used for thorough analysis.

5. Calculating the overall score

By aggregating these sub-scores, considering their respective weights, we arrive at a comprehensive risk rating for each property. Using a formula or algorithm will ensure consistency in calculations. Further validating the scoring system with sample properties will help improve accuracy.

6. Validation and adjustment

It’s vital to validate and adjust the rating system against historical data and expert analysis to ensure its reliability and accuracy. Regularly review and update the criteria and weights based on new data.

Checklist

7. Providing risk mitigation recommendations

Along with the risk score, offering advice on how to reduce a property’s vulnerability to storm surges and hurricanes can be highly beneficial. Suggestions such as upgrading building materials, improving drainage systems or investing in flood barriers can form a checklist of actionable steps to reduce a property’s vulnerability.

8. Regular updates and re-evaluations

Continuously updating the risk rating system to reflect environmental changes, infrastructure developments and updated data is crucial. This includes regular reviews, incorporating new data and tech advancements can improve the risk rating system. 

Building Resilience with Accurate Risk Ratings

Stakeholders can create a robust and reliable risk rating system that enhances safety and preparedness in coastal areas.

A well-developed Storm Surge and Hurricane Risk Rating can provide essential information for making educated decisions about property development, insurance and risk management.

As the world grapples with the increasing challenges of climate change, these tools become ever more critical in our collective efforts to build resilient communities.

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Read more blogs from The Proptech Cloud

Crafting a Storm Surge and Hurricane Risk Rating for Coastal Properties

A high-level approach to developing a storm surge and hurricane risk rating system to guide stakeholders with a vested interest in coastal properties.

How Proptech Is Revolutionising Real Estate

Proptech is the dynamic intersection of property and technology, and it’s reshaping real estate. And there’s still a huge potential for growth.

What is the Australian Statistical Geography Standard (ASGS)?

The ASGS is used to better understand where people live and how communities are formed.

How to Incorporate Mesh Blocks into Datasets

Mesh blocks can enhance the precision and relevance of geospatial and proptech analyses. Here are some tips and steps to incorporate mesh blocks into datasets.

Australia’s Migration Trends: Where Are People Moving To?

This detailed visual analysis for Australia’s major capital cities breaks down how net migration trends are evolving across different regions.

How to Incorporate Mesh Blocks into Datasets

How to Incorporate Mesh Blocks into Datasets

Mesh Blocks in real estate and proptech applications

Mesh Blocks are useful for geospatial and proptech applications, providing granularity and accuracy for understanding local real estate markets, demographics and land use.

The integration of Mesh Blocks into datasets can enhance the precision and relevance of analyses within the proptech and real estate sectors.

Useful in geospatial data and census analyses, embedding Mesh Blocks into digital boundaries enhances their usability in various applications.

We will cover the steps to incorporate mesh blocks into data sets below.

What are Mesh Blocks and how are they used in real estate?

Mesh Blocks are foundational building blocks for geospatial and proptech applications, providing granularity and accuracy for understanding local real estate markets, demographics and land use.

How to incorporate Mesh Blocks into datasets

Incorporating Mesh Block into datasets involves several steps to ensure seamless integration and effective utilisation of geographical information. Here’s a guide on how to incorporate Mesh Blocks into datasets:

Step 1: Data Collection

Gather relevant data that aligns with Mesh Blocks.

This may include demographic information, property values, land use details, or any other dataset that can be associated with specific geographical areas.

 

Step 2: Download Mesh Block Boundaries

Mesh Block boundary files can be downloaded from authoritative sources, such as the Australian Bureau of Statistics (ABS) or relevant statistical agencies.

For ease, The Proptech Cloud has a free comprehensive dataset Geography – Boundaries & Insights – Australia ready for access and immediate use.

Geography – Boundaries & Insights – Australia

This free dataset from The Proptech Cloud is available for seamless access from Snowflake Marketplace.

Step 3: Geospatial Data Processing

Use Geographic Information System (GIS) software or programming libraries (e.g., Python with geospatial libraries like GeoPandas) to process and manipulate the mesh block boundaries.

Tip:

Geographical boundaries can be imported using Python libraries including Geopandas and shapely.

Many data warehouses including Snowflake, BigQuery and PostgreSQL have in-built geospatial functionality to allow for the processing of geospatial data.

QGIS – Loading in Geospatial files in QGIS

1. From the toolbar at the top of the page click Layer > Add Layer > Add Vector Layer

2. Make sure the Source Type is clicked to File

3. Load in the Source Data by using the three dots button at the side of the Vector Dataset(s) toolbar

QGIS - Loading in Geospatial files in QGIS

Geospatial Formats

The two most common ways geospatial data are represented in files are Well-Known-Text (WKT) which is a textual representation of a polygon and the geojson format which shows the coordinates and type of geojson format.

Both Python and Snowflake have capabilities to work with these 3 formats and parse them so they can be used in geography functions

WKT Format

#Example 2 using WKT format

from shapely import wkt

brisbane_bbox = “POLYGON ((153.012021 -27.471741, 153.012021 -27.462598, 153.032931 -27.462598, 153.032931 -27.471741, 153.012021 -27.471741))”

brisbane_poly = wkt.loads(brisbane_bbox)

Python – Loading in GeoJSON

The libraries geojson, shapely and json need to be installed.

#EXAMPLE 1 working with a geojson format

import json

import geojson

from shapely.geometry import shape

geojson_example = {

"coordinates": [[[153.01202116, -27.47174129], [153.01202116, -27.46259798], [153.03293092, -27.46259798], [153.03293092, -27.47174129], [153.01202116, -27.47174129]]],

"type": "Polygon"

}

geojson_json = json.dumps(geojson_example)

# Convert to geojson.geometry.Polygon

geojson_poly = geojson.loads(geojson_json)

poly = shape(geojson_poly ))

Snowflake

GeoJSON and WKT format can also be loaded into snowflake and converted to a geometry using the following commands:

#converting Well-Known-Text into geography format

SELECT ST_GEOGRAPHYFROMWKT('POLYGON ((153.012021 -27.471741, 153.012021 -27.462598, 153.032931 -27.462598, 153.032931 -27.471741, 153.012021 -27.471741))');

#Converting Geojson to geography format

SELECT TO_GEOGRAPHY('{

"coordinates": [[[153.01202116, -27.47174129], [153.01202116, -27.46259798], [153.03293092, -27.46259798], [153.03293092, -27.47174129], [153.01202116, -27.47174129]]],

"type": "Polygon"

}

')

Step 4: Data Matching

Match the dataset records with the appropriate mesh blocks based on their geographical coordinates. This involves linking each data point to the corresponding mesh block within which it is located.

Tip:

Geospatial functions which are supported in big data warehouses and Python can be used to match geospatial data.

A common way to match two geographical objects is to see if the coordinates of the two objects intersect. An example of how to do this in Python and Snowflake is shown below.

In Python

Data matching can be done using the shapely library intersects function.

from shapely import wkt, intersects

shape1 = wkt.loads("POLYGON ((153.012021 -27.471741, 153.012021 -27.462598, 153.032931 -27.462598, 153.032931 -27.471741, 153.012021 -27.471741))")

shape2 = wkt.loads("POLYGON ((153.012021 -27.471741, 153.032931 -27.462598, 153.012021 -27.471741))")

shape_int = intersects(shape1, shape2)

print(shape_int)

 

In Snowflake

Data matching can be done using the ST_Intersects function. One of the advantages of using big data warehouses including Snowflake to geospatially match data is that it leverages its highly scalable infrastructure to quickly complete geospatial processing.

WITH geog_1 as (

SELECT ST_GEOGRAPHYFROMWKT('POLYGON ((153.012021 -27.471741, 153.012021 -27.462598, 153.032931 -27.462598, 153.032931 -27.471741, 153.012021 -27.471741))') as poly

),

geog_2 as (

SELECT ST_GEOGRAPHYFROMWKT('POLYGON ((153.012021 -27.471741, 153.022021 -27.465, 153.032931 -27.462598, 153.012021 -27.471741))') as poly

)

SELECT

g1.poly, g2.poly

FROM geog_1 as g1

INNER JOIN geog_2 as g2

on ST_INTERSECTS(g1.poly, g2.poly)

Step 5: Attribute Joining

If your dataset and mesh blocks data have common attributes (e.g., unique identifiers), perform attribute joins to combine information from both datasets. This allows you to enrich your dataset with additional details associated with mesh blocks.

Step 6: Quality Assurance

Verify the accuracy of the spatial integration by checking for any discrepancies or errors. Ensure that each data point is correctly associated with the corresponding mesh block.

Tip:

geojson.io is a handy website that can help with visualising geojson data and ensure it is correct.

If you’re using Snowflake, the ST_AsGeojson command can be used to convert geography into a geojson which allows you to quickly visualise the shapes created.

Step 7: Data Analysis and Visualisation

Leverage the integrated dataset for analysis and visualisation. Explore trends, patterns, and relationships within the data at the mesh block level. Utilise geospatial tools to create maps and visual representations of the information.

Tip:

It’s worth mentioning that Snowflake has the option to create a Streamlit app within the Snowflake UI which allows for the cleaning and processing of data using Python and SQL and the interactive visualisation of data through the Streamlit App.

Read our blog which demonstrates how to predict migration patterns and create forecasts using Snowpark and Streamlit>

Snowflake also integrates really well with local Python development environments so all the initial data processing and cleaning can be done through a Snowflake API, then geography can be converted to a GeoJson or Text formal. Thereafter, libraries like plotly, folium, pydeck can be used to do complex geospatial visualisations.

Step 8: Data Storage and Management

Establish a system for storing and managing the integrated dataset, ensuring that it remains up-to-date as new data becomes available.

Consider using databases or platforms that support geospatial data.

Tip:

Geospatial datasets are usually very large and complex datasets due to the number of attributes included in a geospatial dataset, the resolution of the data and the number of records.

Cloud-based big data platforms can be an excellent option for storing geospatial data due to the low-cost of storage. Many of these platforms including also have spatial clustering options so that geospatial data in a similar location are grouped together, meaning queries for data in certain areas run more efficiently.

Snowflake (Enterprise Edition or Higher) also has an option to add a search optimisation to geospatial data tables to optimise the performance of queries that use geospatial functions.

Step 9: Documentation

Document the integration process, including the source of mesh block boundaries, any transformations applied, and the methods used for data matching. This documentation is essential for transparency and replicability.

By following these above steps, you can effectively incorporate mesh blocks into your datasets, enabling a more detailed and location-specific analysis of the information at the mesh block level.

 

Geography – Boundaries & Insights – Australia

This free dataset from The Proptech Cloud is available for seamless access from Snowflake Marketplace.

The intellectual property rights for all content in this blog are exclusively held by Data Army and The Proptech Cloud. All rights are reserved, and no content may be republished or reproduced without express written permission from us. All content provided is for informational purposes only. While we strive to ensure that the information provided here is both factual and accurate, we make no representations or warranties of any kind about the completeness, accuracy, reliability, suitability, or availability with respect to the blog or the information, products, services, or related graphics contained on the blog for any purpose.

Subscribe to our newsletter

Subscribe to receive the latest blogs and data listings direct to your inbox.

Read more blogs from The Proptech Cloud

Crafting a Storm Surge and Hurricane Risk Rating for Coastal Properties

A high-level approach to developing a storm surge and hurricane risk rating system to guide stakeholders with a vested interest in coastal properties.

How Proptech Is Revolutionising Real Estate

Proptech is the dynamic intersection of property and technology, and it’s reshaping real estate. And there’s still a huge potential for growth.

What is the Australian Statistical Geography Standard (ASGS)?

The ASGS is used to better understand where people live and how communities are formed.

How to Incorporate Mesh Blocks into Datasets

Mesh blocks can enhance the precision and relevance of geospatial and proptech analyses. Here are some tips and steps to incorporate mesh blocks into datasets.

Australia’s Migration Trends: Where Are People Moving To?

This detailed visual analysis for Australia’s major capital cities breaks down how net migration trends are evolving across different regions.

What Are Mesh Blocks & How Are They Used in Real Estate

What Are Mesh Blocks & How Are They Used in Real Estate

What are Mesh Blocks?

As defined by Australian Bureau of Statistics (ABS), mesh blocks are the smallest geographical area of the Australian Statistical Geography Standard (ASGS) and ABS’s classification of Australia into a hierarchy of statistical areas.

Mesh Blocks are essentially a set of geographic boundaries designed to segment Australia into very small areas. These boundaries are used to apply a systematic grid over the entire country, dividing it into tiny sections called Mesh Blocks.

Each Mesh Block is a polygon that outlines a specific piece of land, which can range from a single block in a city to a vast, sparsely populated area in the countryside.

In 2021, the ABS reported 368,286 Mesh Blocks covering the whole of Australia without gaps or overlaps.

Mesh Blocks covering the whole of Australia. Source: ABS Maps

 

Mesh Block design

Mesh Blocks for the current ASGS Edition 3 are designed according to a standard set of design criteria first developed for ASGS 2011.

Most Mesh Blocks are designed to contain 30 to 60 dwellings, although some low dwelling count Mesh Blocks exist. They are permitted in order to account for other design criteria.

The reasons for the minimum dwelling count of Mesh Blocks is so they’re small enough to aggregate to a wide range of areas, allow comparisons between geographic regions but also prevent accidentally exposing confidential information of individuals or businesses.

 

Mesh Block changes

Mesh Blocks are updated (or redesigned) every 5 years to stay relevant.

Mesh Blocks for the current ASGS Edition 3 was redesigned to ensure it still meets the design criteria first developed for ASGS 2011 and reflects the growth and change in Australia’s population, economy and infrastructure.

Mesh Block Changes

Example of Mesh Block change along the border of Queensland and New South Wales. Source: Australian Bureau of Statistics

How are Mesh Blocks created?

Each Mesh Block is assigned a unique numerical code or identifier. This code is used to reference the Mesh Block in statistical databases and geographic information systems (GIS).

The format of the code can vary but often includes digits that signify hierarchical levels of geography.

In Australia, Mesh Block identifiers are 11-digit codes.

The 11-digit Mesh Block code comprises: State and Territory identifier (1 digit), and a Mesh Block identifier (10 digits).

How are Mesh Blocks used?

The ABS does not and cannot provide detailed segmentation data (Census data) that can be directly connected to individuals or businesses. Instead, they provide anonymised and aggregated data against geographic areas. Mesh Blocks are the smallest geographic area that the ABS provide statistics against, so it offers population and dwelling counts at a hyper-local level – this is particularly useful for Census analysis.

These geographic boundaries allow for the aggregation of data from individual Mesh Blocks into larger geographic units, such as suburbs, towns, cities, and regions. This hierarchical structuring makes it possible to analyse data at various levels, from very detailed local information to broader regional or national trends.

Most businesses, including proptechs, looking to augment their analysis with population segmentation data will adopt Mesh Blocks as their default level geographic unit to gain the highest level of accuracy. The popularity of Mesh Blocks mean many businesses will use it for geographic statistics regardless of whether or not the Census data is being leveraged.

What role do Mesh Blocks play in proptech?

Mesh Blocks play a vital role in Proptech, geospatial data, and the real estate industry in Australia. Some example uses include:

Granular geographical data

Since Mesh Blocks are the smallest geographical units, providing a granular level of detail in geographic data, its precision is valuable for analysing real estate trends at a hyper-local level.

Accurate small area statistics

Mesh Blocks are designed to fulfill the need for accurate small area statistics. In Proptech, having precise data at this level is instrumental for understanding localised property markets, demographics, and trends.

Spatial mapping and analysis

Geospatial data, including Mesh Blocks, facilitates spatial mapping and analysis. Proptech platforms can leverage this data to visualise and analyse property-related information, helping users make more informed decisions based on geographical insights.

Enhanced property valuation

Proptech applications can utilise Mesh Blocks to refine property valuation models. The data on dwellings and residents at this level allows for a more nuanced understanding of property values, considering localised factors.

Land use identification

Mesh blocks broadly identify land use, such as residential, commercial, industrial, parkland, and so forth. Land use information is valuable for proptechs involved in property development, urban planning, and investment strategies.

Targeted marketing and outreach

Proptech businesses can use Mesh Block data to tailor marketing and outreach strategies to specific geographical areas. Understanding the demographics and dwelling counts at this level allows for targeted and effective location-based campaigns.

Census-driven insights

The inclusion of Census data within Mesh Blocks, such as the count of usual residents and dwelling types, provides proptech platforms with up-to-date demographic information. This can aid market analysis, customer profiling, and investment strategies.

Integration with digital boundary files

The availability of Mesh Block boundaries in digital boundary files enhances their usability in Proptech applications. These files can be readily integrated into geospatial systems, making it easier for developers and analysts to work with this geographical data.

The foundational building blocks in real estate

Mesh Blocks are foundational building blocks for geospatial and proptech applications, providing granularity and accuracy for understanding local real estate markets, demographics and land use.

To aid proptechs, The Proptech Cloud offers its Geography – Boundaries & Insights dataset which includes all mesh blocks and their spatial areas for analysis and location-based visualisation of statistics.

The integration of this important information can enhance the precision and relevance of analyses within the proptech and real estate sectors. Read our following blog to learn how to incorporate Mesh Blocks into datasets.

How to Incorporate Mesh Blocks into Datasets

Incorporating mesh blocks into datasets involves several steps to ensure seamless integration and effective utilisation of geographical information. Here’s a guide on how to incorporate mesh blocks into datasets.

Subscribe to our newsletter

Subscribe to receive the latest blogs and data listings direct to your inbox.

Read more blogs from The Proptech Cloud

Crafting a Storm Surge and Hurricane Risk Rating for Coastal Properties

A high-level approach to developing a storm surge and hurricane risk rating system to guide stakeholders with a vested interest in coastal properties.

How Proptech Is Revolutionising Real Estate

Proptech is the dynamic intersection of property and technology, and it’s reshaping real estate. And there’s still a huge potential for growth.

What is the Australian Statistical Geography Standard (ASGS)?

The ASGS is used to better understand where people live and how communities are formed.

How to Incorporate Mesh Blocks into Datasets

Mesh blocks can enhance the precision and relevance of geospatial and proptech analyses. Here are some tips and steps to incorporate mesh blocks into datasets.

Australia’s Migration Trends: Where Are People Moving To?

This detailed visual analysis for Australia’s major capital cities breaks down how net migration trends are evolving across different regions.

Building a Rental Property Automated Valuation Model (AVM)

Building a Rental Property Automated Valuation Model (AVM)

A Rental Automated Valuation Model (AVM) serves as an indispensable tool for a myriad of stakeholders within the property ecosystem.

Besides businesses managing extensive rental portfolios, real estate portals, valuers, banks, and proptech companies, it can also benefit insurance firms, property developers, and governmental housing authorities.

What is a Rental Property Automated Valuation Model?

A rental property automated valuation model (AVM) is a tool which estimates the rent and yield of a property.

What are the Benefits of Owning a Rental Property AVM?

Rental Property AVM

Owning a rental AVM provides a competitive edge through real-time valuation insights, which facilitates informed decision-making regarding rental pricing, portfolio management, and investment strategies.

The benefits of owning a rental AVM extend to enhanced accuracy in rental appraisals, time and cost efficiency, and the ability to customise the model to align with specific business objectives and market dynamics. It paves the way for data-driven strategies, fostering a deeper understanding of market trends and rental property performance.

Therefore, a cautious approach is paramount. Businesses should meticulously evaluate the financial, operational, and regulatory implications before embarking on the development of a rental AVM. A thorough understanding of the costs involved in building, owning, and maintaining such a model is crucial to ascertain the long-term viability and to mitigate the risks associated with this substantial investment.

Embarking on the construction of a Rental Property Automated Valuation Model (AVM) necessitates a well-structured foundation that ensures precision, reliability, and effectiveness in valuing rental properties.

Core Requirements for Building a Rental Property AVM

  1. Address Database:
    A comprehensive address database is indispensable as it serves as the primary reference point for rental properties.
    Each address should have a unique identifier to ensure no duplication or confusion arises in the data.
  2. Geocoding Addresses:
    Geo-coding the addresses is crucial for pinpointing the exact geographical location of each rental property.
    This geo-spatial information is pivotal for applying distance measures which are integral in comparative analysis and valuation.
  3. Back-series Data:
    Accumulating back-series data, ideally spanning at least three years, is fundamental for a nuanced understanding of rental market dynamics over time. Records should include address, property type, rental price, rental date, beds, baths and parking at a minimum.
    This historical data permits the creation of an index to track rental values through time, which is invaluable in comparative market analysis.
    Additionally, back-series data serve as inputs for regression models and machine learning algorithms, providing coefficients essential for adjusting rental prices in a virtual rental comparative market analysis.
  4. IT Resource:
    A proficient IT resource is necessary for building, deploying, and maintaining the database and the rental AVM model.
    They would be responsible for ensuring system efficiency, security, and scalability, ensuring the model adapts to the evolving market dynamics.
  5. Database Resource:
    A dedicated database resource is required to manage the vast amount of data involved in this project.
    They ensure data integrity, accuracy, and availability, which are crucial for the reliability of the AVM.
  6. Organisational Commitment:
    It’s imperative that the organisation has a firm commitment to provide the necessary resources for the successful completion of this project. In the absence of requisite IT and database resources, it might be prudent to reconsider the viability of this project.
Rental Property AVM

Checklist

  • Acquire a comprehensive address database.
  • Implement geocoding for all addresses.
  • Collect a minimum of three years’ worth of back-series data.
  • Secure a skilled IT resource for system development and maintenance.
  • Have a dedicated database resource for data management.
  • Evaluate organisational resource availability and commitment to the project.

This section lays the groundwork for what is needed to commence the journey towards creating a robust Rental Property Automated Valuation Model. Each requirement is pivotal and necessitates careful consideration and planning.

Typical Build Requirements for Rental Automated Valuation Model (AVM)

Creating a reliable and efficient Rental Automated Valuation Model (AVM) necessitates a meticulous approach towards the build requirements. Here’s a high-level outline of the components and processes involved:

  1. Database:
    Establishing a robust database to store and manage the diverse set of data involved in the valuation process.
  2. Index:
    Creating an index to track and compare rental values over time.
  3. Weekly Rental Data Source:
    Securing a reliable source of weekly rental data to keep the model updated with current market conditions.
  4. ETL Process:
    Designing an Extract, Transform, Load (ETL) process to handle rental data, including filtering, standardisation, duplicate removal, and data hierarchy management.
  5. Address and Geospatial Service:
    Ensuring an ongoing service for address verification and geospatial data.
  6. Reports:
    Generating reports encompassing medians, data management records, and dashboards for insightful analysis. This should also include error reports.
  7. Lookups:
    Developing lookup functions to standardise and categorise data fields, aiding in data accuracy and consistency.
  8. Outlier Management:
    Implementing systems to identify and manage outliers and influential observations, preventing erroneous data entry.
  9. Model Framework:
    Creating a framework to index the last rental price and to match comparable rentals automatically, akin to a rental Comparative Market Analysis (CMA).
  10. Machine Learning Integration:
    Incorporating machine learning functions to test and adjust model iterations per suburb or locale, ensuring precise valuation.
  11. Extended Features:
    Adding features like street details and information about strata buildings to enhance the model’s accuracy and comprehensiveness.
  12. Regular Training:
    Implementing a regular training schedule to keep the model updated and improve its predictive accuracy over time.

This outline is designed to provide a clear roadmap towards building a robust Rental AVM. While not exhaustive, it encompasses the critical aspects that require consideration to ensure the successful deployment and operation of the model.

Each of these components will be elaborated upon in the subsequent sections, providing a deep dive into the intricacies involved in each stage of the development process.

Part 1: Database Construction for Rental AVM

The cornerstone of developing a robust Rental Automated Valuation Model (AVM) is the establishment of a comprehensive and well-structured database.

This database will serve as the repository of all pertinent information required to perform nuanced and accurate rental valuations. Here are some critical considerations and steps involved in setting up the database:

  1. IT Resource with Property Database Skills: Having an IT resource with expertise in property databases is indispensable for this endeavour. The intricate nature of property data and the rental market dynamics necessitate a deep understanding and skilled handling of the data.
  2. Utilisation of Geoscape Database: In Australia, leveraging the government-maintained Geoscape database could serve as an ideal foundation due to its comprehensive property data schema. This database encompasses critical geospatial and address information which is paramount for accurate rental valuations.
  3. Incorporation of Rental Data Tables: Rental data tables should be meticulously designed and integrated within the Geoscape schema or an alternative robust schema. These tables will hold the rental data, both current and historical, for each property.
  4. Time-Series Data Storage: A common pitfall for novices is the improper handling of time-series data. It’s crucial to design the database such that the same property record can be stored through time, capturing all rental transactions and changes in property attributes.
  5. Derivative Metrics and Indexation: Storing all time-series and historical data facilitates the creation of derivative metrics and indices. These metrics, like indexation, provide insightful trends and comparative measures for rental valuations.
  6. Comprehensive Attribute Storage: The database should accommodate the storage of a plethora of attributes for each rental. This includes not only the rental price history but also details about the address, street, building, and locale data.
  7. Data Integrity and Consistency: Ensuring data integrity and consistency is paramount. Implementing stringent data validation and verification processes will aid in maintaining a high level of data accuracy.
    A well-architected database is the bedrock upon which the other components of the Rental AVM are built. It requires a meticulous design, skilled resources, and an ongoing commitment to data management to ensure the reliability and accuracy of the rental valuations generated by the AVM.

Part 2: Index Construction for Tracking and Comparing Rental Values

Creating an index is a fundamental aspect of a Rental Automated Valuation Model (AVM) as it provides a mechanism to track and compare rental values over time, thereby offering a quick and effective way to update rental prices to reflect current market conditions.

Here are the key considerations and methods involved in index construction:

  1. Instantaneous Price Updating: The index enables immediate price updating based on the last advertised rent or the last rental Comparative Market Appraisal (CMA), aligning the prices with the current market trend.
  2. Monthly Database Indexing: Each month, the entire database and portfolio are indexed to ensure the rental values remain relevant and reflective of the prevailing market dynamics. This method remains effective typically for up to 3 or 4 years.
  3. Automated CMA Adjustment: The index adjusts the comparative rentals used in the automated CMA, facilitating the matching of nearby rentals for up to 12 months while ensuring the price estimate remains in sync with market movement.
  4. Median-Based Indexing: One simplistic approach to index construction is utilizing the median rental value for a given area. In Australia, medians are often measured at a Statistical Area 3 (SA3) basis, which can be imported and utilized directly, or recalculated as needed. This approach can extend to smaller areas like SA2 or suburb level, provided there’s a significant rental sample each month to mitigate excessive volatility.
  5. Property Type Segmentation: It’s imperative to measure the median after categorising rentals by logical property types such as houses (including terraces) and units (including apartments, townhomes, flats, and villas). Further subdivision into sub-market groups may be feasible depending on the location and data availability.
  6. Repeat-Rental Indexing: Another nuanced approach involves tracking the change over time of repeat rentals. In a design akin to a repeat-rental-index, rentals with two prices spanning 1 to 5 years are entered into the model. This method, albeit more complex, could provide a deeper insight into rental value trends and may be worth exploring depending on the project scope and budget.
  7. Custom Index Calculation: For those with adequate resources, developing a custom index at a more granular level could provide more precise and tailored insights, aiding in a more accurate rental AVM. The construction of a robust index is a nuanced process that requires a strategic approach. Whether opting for a median-based index or exploring the repeat-rental indexing method, the goal is to ensure the index accurately captures the rental market dynamics, aiding in the effective operation of the Rental AVM.
Rental Property AVM

Part 3: Procurement of Weekly Rental Data Source

Ensuring a consistent and reliable source of weekly rental data is paramount for the effective operation and accuracy of a Rental Automated Valuation Model (AVM).

A diligent update on a weekly basis keeps the model attuned to the prevailing market conditions, thereby enhancing the precision in rental valuations.

Here are some key considerations:

  1. Data Relevance: Advertised rentals have long served as a credible source for rental price models and are widely recognised in the industry. Alternatively, some advocate for using final contracted rental prices, although procuring such data on a national scale may pose challenges. Either of these data sources can be utilised based on availability and project requirements.
  2. Data Attributes: The rental data procured should comprehensively capture crucial attributes including:
    Full address (preferably pre-geocoded).
    Property type (requiring standardisation via lookups in most cases).
    Number of bedrooms, bathrooms, and parking spaces.
    Rental date and rental price.
  3. Geocoding and GNAF PID Matching (for Australia): In the Australian context, matching the address to a Geocoded National Address File (GNAF) PID is beneficial for ensuring precise location identification.
  4. Unique Identifier Establishment: While the address serves as a primary identifier, it’s vital to distinctly identify the street and strata (apartment) building, which can act as unique matching identifiers aiding in accurate data matching and analysis.
  5. Standardisation: Standardising data, especially the property type, through lookups ensures consistency across the dataset, which is critical for accurate comparative analysis and valuation.
    This procurement and structuring of weekly rental data form the crux of maintaining a dynamic and responsive Rental AVM, allowing for real-time insights and a thorough understanding of the rental market trends.

Part 4: Designing a Robust ETL Process for Rental Data Management

The Extract, Transform, Load (ETL) process is a critical pillar in the data management framework of a Rental Automated Valuation Model (AVM). It ensures that rental data is accurately harvested, refined, and loaded into the database for optimal utilisation.

Below are the key components and considerations in designing an effective ETL process:

  1. Duplicate Handling: An efficient mechanism to identify and handle duplicates is crucial to maintain data integrity. When the same record is collected from different sources, a hierarchy or trust rating system should be in place to select the more reliable source.
  2. Data Standardisation: Rental data often requires standardisation, especially when it comes to free-text fields. Utilising tools like ChatGPT can significantly aid in converting free-text data into a structured and standardised format.
  3. Data Filtering: Implementing filters to weed out irrelevant or erroneous data is essential to ensure the quality and reliability of the information being loaded into the database.
  4. Local Expertise: In Australia, leveraging local expertise in the ETL domain can expedite the deployment of a fit-for-purpose ETL solution for real estate data, bypassing the steep learning curve associated with standard ETL tools.
  5. Customised ETL Solution: Although off-the-shelf ETL tools are an option, a customised solution tailored to handle real estate data peculiarities can be more beneficial in the long run. This can be achieved by collaborating with experts who have a deep understanding of the Australian real estate data landscape.
  6. Continuous Learning and Improvement:  The ETL process will likely require fine-tuning over time. Learning from the data handling experiences and continuously improving the ETL process is pivotal for achieving and maintaining a high level of data accuracy and efficiency.

The design and implementation of a robust ETL process is a meticulous task that demands a blend of the right technology, expertise, and a thorough understanding of the real estate data ecosystem. This ensures that the rental AVM operates on a foundation of accurate, reliable, and well-structured data.

Part 5: Address and Geospatial Service Integration

A dedicated service for address verification and geospatial data management is indispensable in refining the accuracy and reliability of a Rental Automated Valuation Model (AVM).

Below are pivotal considerations and tools:

  1. Address Verification: Utilising Australia’s Geocoded National Address File (GNAF) is an exemplary method for precise address verification. However, third-party services also offer valuable solutions for rectifying poor quality addresses collected via free text inputs.
  2. Geospatial Data Layer: Incorporating a geospatial layer enhances the model’s efficiency in matching comparable properties by providing spatial insights. It aids in better understanding the proximity and locational advantages of properties, which are crucial factors in rental valuations.
  3. Data Repair and Standardisation: Leveraging services that can repair and standardise address data is vital to ensure consistency and accuracy in the database. This is particularly important when the initial data collection may have inconsistencies due to free text entries.
  4. Continuous Service: Engaging a continuous service for address and geospatial data management ensures the model remains updated with accurate locational data, aiding in the precise valuation and comparison of rental properties.

The integration of robust address verification and geospatial data services fortifies the model’s foundation, ensuring precise and meaningful insights in rental valuation and comparative analysis.

Part 6: Report Generation for Insightful Analysis and Performance Monitoring

Generating comprehensive reports is a vital component in the management and continuous improvement of a Rental Automated Valuation Model (AVM).

These reports provide a clear picture of the model’s performance, data management efficiency, and areas requiring attention.

Key considerations include:

  1. Error Reporting: Essential error reports like Forecast Standard Deviation (FSD) and Percent Predicted Error (PPE10) provide invaluable insights into the accuracy of rental valuations. For instance, calculating the percentage and dollar value error as a new rental record enters the database facilitates immediate performance assessment. Records with AVM estimates within 10% of the actual rental price can be flagged, enabling the calculation of properties estimated within a 10% accuracy range, which can be reported by property type, suburb, or broader geographical areas.
  2. Median, Volume, and Hit-Rate Reporting: Reports displaying median rental values, the volume of rental records entering the database, and the hit-rate (the proportion of records for which an AVM can be generated) are crucial for evaluating data management efficiency and model coverage.
  3. Dashboard Creation: Designing dashboards that encapsulate key metrics provides a succinct overview of the model’s performance, aiding in prompt decision-making and continuous improvement.
  4. Monthly Tracking: Monthly tracking of error rates, hit-rates, and other key metrics enables trend analysis, which is instrumental in identifying areas of improvement and assessing the impact of any modifications made to the model.
  5. Customised Reporting: Tailoring reports to meet specific organisational needs ensures that the insights generated are aligned with the objectives and requirements of managing the rental AVM effectively.

Through diligent report generation and analysis, stakeholders can maintain a firm grasp on the model’s performance, the quality of data management, and the accuracy of rental valuations, which are integral for the successful operation and continuous refinement of the Rental AVM.

Rental Property AVM

Part 7: Lookups: Enhancing Data Accuracy and Consistency

Implementing lookup functions is a pivotal step in managing the database effectively, ensuring data standardisation, and categorising data fields to bolster accuracy and consistency in a Rental Automated Valuation Model (AVM).

Here are some critical aspects and benefits of developing lookup functions:

  1. Standardisation of Property Types: Different regions or states may employ varied standards for defining property types. Lookup tables can harmonise these discrepancies by mapping varied definitions back to a standard classification, ensuring uniformity across the dataset.
  2. Correction of Free Text Errors: Free text entries are prone to inconsistencies and errors. Lookup functions can be employed to identify common errors and rectify them, thereby enhancing the quality of data.
  3. Utilisation of ChatGPT: Leveraging ChatGPT can expedite the setup and maintenance of lookups significantly. With its capability to process and standardise free text, ChatGPT serves as a valuable tool in automating the correction of common errors and inconsistencies, thereby reducing manual effort and enhancing accuracy.
  4. Dynamic Error Correction: Over time, new errors or discrepancies may emerge. A dynamic lookup function, aided by ChatGPT, can adapt to new patterns, facilitating ongoing data quality maintenance.
  5. Enhanced Database Management: Lookup functions contribute to a structured and well-managed database, which is foundational for generating accurate rental valuations and insightful analysis.
  6. Support for Automated Processing: Lookups support automated data processing by ensuring data fields are standardised and categorised correctly, which is crucial for the efficient operation of the AVM.
  7. Reduced Data Cleaning Overheads: By automating the process of error correction and standardisation, lookups reduce the time and resources required for data cleaning, enabling a more streamlined and efficient database management process.
  8. Improved Model Performance: Standardised and accurate data significantly contribute to the overall performance and reliability of the rental AVM, ensuring that the valuations generated are reflective of the actual market conditions.

The development and continuous refinement of lookup functions are instrumental in fostering a high level of data integrity and operational efficiency in managing the rental AVM.

Part 8: Outlier Management: Safeguarding Against Erroneous Data Entry

Rental Property AVM

Effective outlier management is crucial to maintain the integrity and accuracy of a Rental Automated Valuation Model (AVM).

Outliers and influential observations, if not handled appropriately, can lead to skewed valuations and misrepresentations of the rental market.

Here’s how to approach outlier management:

  1. Identification of Outliers: Outliers can be spotted based on extreme rental price values. Utilising the 1.5*Interquartile Range (IQR) rule is a standard measure, but it’s essential to apply this rule carefully to prevent inadvertent removal of valid records.
  2. Sampling Strategy: Employing a well-thought-out sampling strategy, such as examining a suburb sample over 12 months by property type, is crucial. A carefully curated sample minimises the risk of erroneously identifying valid records as outliers.
  3. Multivariate Analysis: Incorporating multivariate analysis helps in identifying records that significantly impact the model performance upon their entry into the rental AVM. This approach is vital in spotting observations that may skew the model outcome.
  4. Influential Observation Metrics: Measures such as Cook’s Distance are standard for identifying influential observations. Integrating such metrics into the model aids in recognising and managing observations that could disproportionately affect model performance.
  5. Automated Outlier Detection: Developing automated systems for outlier detection and management can enhance efficiency and accuracy in maintaining data quality. It also ensures a timely response to erroneous data entries.
  6. Continuous Monitoring and Adjustment: Continuous monitoring and adjustment of the outlier management system is crucial to keep pace with evolving data trends and to ensure the ongoing effectiveness of the outlier detection mechanisms.
  7. Documentation and Review: Documenting outlier occurrences and reviewing the outlier management processes regularly provide insights for improvement and ensure a clear understanding of the model’s performance dynamics.
  8. Integration with Reporting: Integrating outlier management insights into the reporting framework provides a comprehensive view of data quality and model performance, enabling informed decision-making and continuous improvement.

By adopting a meticulous approach to outlier management, the robustness and reliability of the Rental AVM are significantly enhanced, ensuring that the valuations generated are a true reflection of the rental market conditions.

Part 9: Developing a Robust Model Framework for Rental AVM

The creation of a model framework for a Rental Automated Valuation Model (AVM) is a nuanced undertaking that goes beyond just feeding massive datasets into machine learning models.

It entails crafting a systematic approach that mirrors the methodical selection of comparable rentals, akin to a rental Comparative Market Analysis (CMA), while also ensuring accurate indexation of the last rental price.

Here’s an outline of the core components and considerations in developing such a framework:

  1. Matching Algorithm Design: The foundation of the model is the creation of a matching algorithm that accurately pairs comparable rentals to the subject property. This algorithm takes into account variables such as time, distance, bedroom count, bathroom count, and parking availability. A perfect match scores 100%, with a desirable match rate being 70% or better. The weights assigned to each variable in the matching algorithm can be fine-tuned at a suburb, postcode, or even broader geographical level, and further boosted for comparables within the same street or building.
  2. Utilisation of Advanced Tools: The advent of advanced tools like ChatGPT significantly enhances the model, especially when enriched with geospatial data, images, text, or maps. Even preliminary tests with ChatGPT have shown promising results in refining the matching algorithm, indicating a potential for substantial model improvement.
  3. Grid Adjustment Coefficients: This aspect of the model accounts for adjustments needed over time, or for differences in bedroom, bathroom counts, and parking availability. Additional variables like floor levels and aspect could be integrated in select scenarios. These coefficients can be stored as either dollar values or percentages, with percentages often proving more robust.
  4. Continuous Training and Refinement: The matching scores and grid adjustment coefficients should be subjected to continuous training, testing, and refinement, exploring thousands of permutations to enhance accuracy. This iterative process can be expedited using ChatGPT or standard statistical code, aiding in the monthly or periodic retraining of the model.
  5. Professional Deployment and Maintenance: Storing the matching coefficients in database tables and ensuring professional deployment and maintenance of the model is crucial for sustaining its performance and reliability.
  6. Avoidance of Overfitting: Steering clear of overfitting by embracing model designs evolved over years, which emulate appraiser or real estate agent methodologies in selecting comparables, is imperative to prevent catastrophic model failures.

This structured approach to developing a model framework not only aligns with traditional appraisal methodologies but also harnesses modern tools to significantly enhance the accuracy and reliability of the Rental AVM.

Part 10: Integrating Machine Learning for Precise Valuation in Rental AVM

The infusion of machine learning (ML) into the Rental Automated Valuation Model (AVM) framework presents an avenue for enhancing valuation precision across different suburbs or locales.

While ML facilitates rapid model deployment, a siloed ML approach often falls short due to overfitting and lack of inclusivity in a broader model framework.

Moreover, the opacity of ML models, where the specific comparables used for a rental property estimate remain unidentified, poses a challenge.

The common reflex to attribute poor model results to inadequate data further underscores the limitations of a standalone ML approach.

  1. Enhancing Traditional AVMs: The integration of ML into time-tested, industrial-grade AVMs, honed over two to three decades, offers a pragmatic solution. This fusion capitalises on the strengths of both ML and traditional AVM methodologies, mitigating the shortcomings of a solitary ML approach.
  2. ChatGPT Integration: Incorporating ChatGPT, an advanced tool, into the AVM framework can significantly augment the matching scores and functionality. It opens new vistas for processing and utilising data beyond existing quantitative measures, thereby pushing the boundaries of what can be achieved in rental valuation precision.
  3. Transparent ML Approaches: Exploring ML approaches that offer a level of transparency, and integrating them with existing AVM frameworks, can provide a more comprehensive, understandable, and reliable rental valuation model.
  4. Continuous Evaluation and Adjustment: Regularly evaluating the ML-integrated AVM, and making necessary adjustments based on the insights garnered, is crucial to maintain the model’s accuracy and relevance in a dynamic rental market.
  5. Collaborative Development: Encouraging a collaborative milieu between ML practitioners, real estate experts, and AVM developers can foster the creation of more robust, transparent, and effective rental valuation models.

In summary, a judicious integration of ML, especially with tools like ChatGPT, into established AVM frameworks can herald a significant leap in achieving precise and reliable rental valuations, while overcoming the inherent limitations of a standalone ML model.

Part 11: Extended Features: Enriching Model Accuracy and Comprehensiveness

Introducing extended features such as street details and information about strata buildings enriches the Rental Automated Valuation Model (AVM), amplifying its accuracy and comprehensiveness. Here’s an exploration of how these extended features and new data sets can be integrated to enhance the model:

  1. Population-Level Data: The value of new data is often directly proportional to its coverage across properties. Data at or near population level, applicable across all properties, is deemed more valuable as it provides a comprehensive enhancement to the model.
  2. Strata Buildings and Street Details: Detailed information about strata buildings and street-level data provide nuanced insights that refine rental valuations. They account for variables like the desirability of a location, the quality of local infrastructure, and the proximity to amenities, which are critical for precise rental appraisals.
  3. ChatGPT and AI Integration: The integration of ChatGPT and AI technologies unlocks the potential to process and utilise diverse data sets like mapping and geospatial data, free text, and images. This integration paves the way for extracting valuable insights from unconventional data sources.
  4. Geospatial Data: Geospatial data can provide crucial contextual information regarding a property’s location, proximity to essential amenities, and the overall desirability of the area, significantly impacting rental valuations.
  5. Free Text and Image Analysis: Utilising ChatGPT for processing free text and image data can help in extracting valuable information that can be integrated into the model. For instance, textual descriptions or images from rental listings can provide insights into a property’s condition, features, and appeal.
  6. Exploration of New Data Sets: Continuous exploration of new data sets, especially those available at a broader scale, is essential. Evaluating the impact of these data sets on model performance ensures that the model remains robust and reflective of current market conditions.
  7. Iterative Enhancement: An iterative approach to integrating and evaluating extended features ensures that the model evolves in line with advancements in data availability and technology.

In essence, the incorporation of extended features, leveraged through advancements in AI and tools like ChatGPT, presents an avenue for elevating the accuracy, reliability, and comprehensiveness of the Rental AVM, thereby ensuring that it remains a robust tool for rental valuation in a dynamic real estate market.

Part 12: Regular Training: Ensuring Optimal Model Performance Over Time

A systematic schedule for regular training is pivotal for maintaining and enhancing the predictive accuracy of the Rental Automated Valuation Model (AVM).

Models are susceptible to degradation over time due to evolving market conditions, hence the imperative for periodic re-tuning and re-training using updated data sets. Here are the key considerations and steps for implementing a regular training schedule:

  1. Data Sample Selection: Careful selection of the data sample for training is crucial. A bias towards more recent data is advisable, yet attention must be paid to ensuring sufficient sample sizes to avoid statistical anomalies.
  2. Handling Outliers and Influential Observations: Vigilant management of outliers and influential observations is essential to prevent deleterious impacts on the model. These can skew the training process and lead to inaccurate predictions.
  3. Geographical Area Selection: In instances where suburb samples are too sparse, expanding the geographical area for data sampling is a prudent step to ensure a robust training process.
  4. Continuous Performance Monitoring: Regular performance monitoring, facilitated through comprehensive reporting, enables tracking of model performance over time. This is crucial for diagnosing issues and understanding the impact of market shifts on the model.
  5. Adaptive Training Schedules: The training schedule should be adaptive to the model’s performance and the availability of new data. This flexibility ensures the model remains attuned to the current market conditions.
  6. Utilisation of Updated Technologies: Employing updated technologies and methodologies for the training process ensures the model benefits from the latest advancements in data processing and machine learning.
  7. Performance Evaluation: Post-training evaluation is vital to ascertain the effectiveness of the training process, and to identify areas for further improvement.
  8. Feedback Loop: Establishing a feedback loop between the training process and model performance evaluation fosters a culture of continuous improvement, ensuring the model’s predictive accuracy is continually honed.
  9. Documentation and Analysis: Documenting the training processes, methodologies, and performance metrics is essential for a thorough analysis, facilitating informed decision-making for future training schedules.

Implementing a meticulously designed regular training schedule, coupled with continuous performance evaluation and adaptive methodologies, ensures that the Rental AVM remains a reliable, accurate, and robust tool for rental valuation amidst the dynamic real estate market landscape.

Rental Property AVM

AVM: A Robust, Precise Tool for Rental Valuation

Constructing a Rental Automated Valuation Model (AVM) entails a meticulous assembly of various modules, each critical for optimal performance.

It commences with database establishment and data acquisition, proceeding to index creation, ETL process design, and geospatial service integration.

Essential reports and lookups ensure data accuracy, while outlier management safeguards against erroneous data.

A robust model framework facilitates comparable rental matching, enriched by machine learning integration and extended features like street details.

Regular training, underpinned by an adaptive schedule and continuous performance evaluation, ensures the model’s predictive accuracy and reliability are maintained, making the Rental AVM a robust, precise tool for rental valuation in a dynamic real estate market.

This article is written by Kent Lardner and was first published by suburbtrends.

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Coordinate Reference Systems (CRS) and Geodetic Datums: What’s the difference?

Coordinate Reference Systems (CRS) and geodetic datums are both used to represent the Earth’s surface, but they are different concepts, and importantly, serve different purposes. We provide definitions, highlight their differences and considerations for practical applications.

Coordinate Reference System (CRS)

A CRS is a coordinate-based system that provides a standardised framework for describing and locating points on the Earth’s surface. CRS is primarily used to represent specific locations on the Earth’s surface with precision and consistency.

A CRS can also be referred to as a spatial reference system (SRS) in many cases.

It defines a set of coordinates that can be used to represent the location of a point on the Earth’s surface.

A CRS typically includes a reference point (an origin), a set of axes (coordinate axes), and a unit of measurement (such as metres).

Geodetic Datum

A geodetic datum, on the other hand, is a mathematical model that defines the shape and size of the Earth’s surface, as well as the location of a reference point (the geodetic origin) and the orientation of the axes.

A geodetic datum provides the framework for measuring and comparing positions on the Earth’s surface.

It includes parameters describing the Earth’s ellipsoidal shape (semi-major and semi-minor axes), the flattening of the Earth, and the position of the datum origin.

Geodetic datums are essential for achieving high accuracy in geospatial measurements, especially over large areas.

What’s the difference?

While a CRS and a geodetic datum both provide frameworks for representing the Earth’s surface, they are different in their scope and purpose.

They serve distinct purposes in spatial representation and measurement.

The main differences between Coordinate Reference Systems and Geodetic Datums

Coordinate Reference Systems (CRS)Geodetic Datums
USESA CRS is used to represent the location of a point on the Earth's surfaceA geodetic datum is used to define the shape and size of the Earth's surface and the reference point used to measure positions
PRIMARY FOCUSA CRS deals primarily with coordinate systemA geodetic datum deals with the underlying shape and size of the Earth's reference ellipsoid
DEFINITIONSCRS definitions typically remain consistentGeodetic datums may evolve over time due to improvements in measurement techniques and advancements in geodesy
OPTIONSMultiple CRS are availableMultiple geodetic datums are available

It’s important to note that in many cases, CRSs are defined based on specific geodetic datums, ensuring compatibility and accuracy in spatial representations.

For example, the UTM system uses the WGS84 geodetic datum.

The decision between which CRS or geodetic datum to use

There are multiple choices of both CRS and geodetic datums available for users to select from.

The choice of CRS and geodetic datum depends on various factors such as the geographic region, application, and desired level of accuracy.

Geographic Region

Geographic Region

Different regions of the world may use specific CRS and geodetic datum combinations that are optimised for that region’s geographical characteristics.

Learn about the geodetic datums we use and reference in Australia.

Applications

Application

The type of application you’re working on can influence your choice of CRS and geodetic datum.

For example, surveying and mapping applications often require high accuracy, so a CRS and geodetic datum that offer precision are chosen. On the other hand, less accurate CRS and datum choices may be suitable for applications like general-purpose Geographic Information Systems or web mapping.

Accuracy

Desired Level of Accuracy

The level of precision required for a particular project or task is a crucial deciding factor. Some CRS and geodetic datum combinations are designed to provide centimetre-level accuracy, while others may provide accuracy at the metre or even decimetre level. So the choice really depends on the project’s specific accuracy requirements.

In practice, these above factors need to be carefully considered to ensure users choose the CRS and geodetic datum that is appropriate and aligns to their needs.

Considerations include whether it accurately represents geospatial data, can be integrated seamlessly with other data sources or used in specific analysis or modeling purposes. This will help avoid errors and inconsistencies in geospatial data handling and analysis.

Practical uses for CRS and geodetic datums

In practical terms, when working with geospatial data and mapping, you often need to specify both the CRS and the geodetic datum to ensure accurate and consistent spatial referencing and calculations. Keep in mind different geographic regions and applications may use specific datums and CRS to meet their needs, so understanding the distinction between them is essential for accurate geospatial referencing and analysis.

How to set these in Snowflake

If using a Geography data type the CRS used is WGS 84 and cannot be changed.

If using the Geometry data type, the CRS (or SRS) can be set with the ST_SETSRID function. To change the CRS of a geometry, use the ST_TRANSFORM function.

SELECT
ST_TRANSFORM(
ST_GEOMFROMWKT('POINT(389866.35 5819003.03)', 32633),
3857
) AS transformed_geom;

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