Coordinate reference systems Archives

What is a Coordinate Reference System (CRS)?

Sep 12, 2024 | Data Domain

TL;DR

A Coordinate Reference System (CRS) is a framework that uses coordinates to accurately locate places on Earth’s surface.

In real estate, CRS is crucial for defining property boundaries, aiding in surveys, mapping, and even in property valuation.

There are different types of CRS, each serving specific mapping needs.

For property and urban planning, CRS ensures precise land registration, zoning, and infrastructure development, helping reduce disputes and enhance planning accuracy.

Imagine you’re taking part in a global treasure hunt or a real-life challenge like The Amazing Race, where the Earth itself is your game board. To navigate to your next destination, you rely on a giant map. But how do you know where exactly to go? You need a set of rules to interpret the map accurately and describe specific locations.

This is where a Coordinate Reference System (CRS) comes in.

Think of CRS like a universal language for maps, providing a framework for assigning coordinates (like X and Y on a grid) to different locations on Earth.

With this system in place, everyone can refer to the same locations using a consistent method, ensuring clarity and accuracy when navigating or sharing geographic data.

Let’s dive deeper into what a CRS is and why it’s essential for interpreting the world around us.

Coordinate Reference System (CRS)

A Coordinate Reference System (CRS) is a system that uses numbers to precisely pinpoint locations on maps or the Earth’s surface, ensuring everyone uses the same rules for describing positions.

By defining sets of coordinates and a standardised framework, it offers a consistent way to specify locations, making it possible for maps and geographic data to be accurately interpreted and shared.

A CRS typically includes a reference point, a set of axes, and a unit of measurement.

What is a CRS used for?

A Coordinate Reference System (CRS) is used to accurately represent, map, and interpret coordinates in a specific geographic or projected space. It enables precise location referencing on the Earth’s surface, ensuring that geographic data can be shared and understood consistently.

CRS is widely used in geography to study the Earth’s physical features, environments, and human interactions with these landscapes. It’s also crucial in cartography, where it ensures that maps are created with accurate geographic information, allowing for reliable navigation and analysis across various fields and applications.

Different Types of CRS

Geographic CRS: Based on a spherical or ellipsoidal model of the Earth’s surface, commonly using latitude and longitude coordinates.
Projected CRS: Maps the three-dimensional spherical or ellipsoidal Earth onto a two-dimensional plane, such as a map or a flat surface. Examples include Universal Transverse Mercator (UTM) and State Plane Coordinate Systems.
Vertical CRS: Specifies elevations or depths relative to a reference surface (e.g., sea level).

Some examples of commonly used CRS include:

Universal Transverse Mercator (UTM) system,
Geographic Coordinate System (GCS), and the
Military Grid Reference System (MGRS).

Practical applications of CRS in property and real estate

Coordinate Reference Systems (CRS) play a vital role in real estate and proptech by providing a standardised way to accurately represent geographic locations. Here are some practical applications:

Property Mapping and Visualisation

CRS allows for exact delineation of property boundaries, and accurate property boundaries are essential for legal and planning purposes.
CRS can be used by proptechs to create interactive property maps, allowing users to explore listings in a spatial context.

Location-Based Services

CRS can be used to calculate distances between properties and amenities like schools, parks, or public transport for proximity analysis.
Create virtual boundaries, or geofences, around properties for targeted marketing or notifications.

Urban Planning and Development

Ensure new developments comply with local zoning regulations by accurately positioning them within zoning maps.
Precise spatial data derived from CRS can be used in the planning of utilities and infrastructure for new real estate developments

Property Valuation

Accurately analyse and compare property locations, boundaries and size, and their impact on value.
Determine a property’s elevation and proximity to flood zones for risk assessment and insurance purposes.

Virtual and Augmented Reality

Virtual property tours are possible with the creation of georeferenced 3D models of properties.
Overlay property information on real-world views using mobile devices for use in augmented reality applications.

Data Integration and Analysis

Combine property data with other geographic information like demographics, crime rates, or environmental data for comprehensive analysis.
Perform complex spatial queries to identify properties meeting specific geographic criteria.

As can be seen in these examples, by leveraging Coordinate Reference Systems, real estate professionals and proptech companies can provide more accurate, data-driven services and make better-informed decisions based on spatial relationships and geographic context.

Originally published: 4 October, 2023

Last updated: 12 September, 2024

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How To Set Coordinate Reference Systems (CRS) In Snowflake Using Spatial Reference Identifiers

Jul 30, 2024 | Technology Application

In previous blogs, we’ve covered off what Coordinate Reference Systems (CRS) are, its scope and uses.

In this blog, we’ll cover how to set these on the Snowflake platform for geospatial referencing and analysis.

In Snowflake, you can define the Coordinate Reference System (CRS) by specifying a spatial reference identifier (SRID), which is a unique code that tells you which map or coordinate system you’re using, including its tolerance and resolution (or in other words, how precise and accurate it is).

TL;DR

If using the GEOGRAPHY data type in Snowflake, you won’t need to set the CRS, as it will be automatically set as WGS 84.

To set the CRS of a GEOMETRY data type, determine its SRID, then use the ST_SETSRID() function.

If not explicitly set, the SRID of a GEOMETRY column will be 0.

To convert from one CRS to another CRS on a GEOMETRY column, use the ST_TRANSFORM() function.

Overview

Coordinate Reference System

A Coordinate Reference System (CRS) defines how the two-dimensional, projected map in your GIS relates to real places on the earth. It encompasses:

Datum: Defines the position of the spheroid relative to the centre of the earth.
Projection: Converts the 3D surface of the earth to a 2D map.
Coordinate system: Defines how the coordinates relate to positions in the real world.

Spatial Reference System Identifier (SRID)

An SRID is a unique identifier associated with a CRS. It is a numeric value that references a specific CRS definition in a spatial database or standard, like the EPSG (European Petroleum Survey Group) codes.

Key Points

CRS is the comprehensive system that includes all the information needed to translate between coordinate systems and real-world positions.

SRID is an identifier for a specific CRS.

Example:
EPSG:4326 is a common SRID, where 4326 is the SRID that corresponds to the WGS 84 CRS (used by GPS).

What are the benefits of setting SRID in Snowflake?

Setting up an SRID in Snowflake ensures data consistency by aligning all spatial data to the same coordinate system, enhancing accuracy with precise tolerance and resolution information.

It facilitates interoperability between systems, enables advanced geospatial analysis and maintains data integrity by providing a defined coordinate framework.

This allows users to perform complex spatial queries efficiently in Snowflake.

How to set CRS and SRID in Snowflake

Snowflake provides the following data types for geospatial data:

The GEOGRAPHY data type, which models Earth as though it were a perfect sphere.
The GEOMETRY data type, which represents features in a planar (Euclidean, Cartesian) coordinate system.

The GEOGRAPHY data type follows the WGS 84 standard (spatial reference ID 4326).

The GEOMETRY data type represents features in a planar (Euclidean, Cartesian) coordinate system.

The coordinates are represented as pairs of real numbers (x, y). Currently, only 2D coordinates are supported.

The units of the X and Y are determined by the spatial reference system (SRS) associated with the GEOMETRY object. The spatial reference system is identified by the SRID number.

Unless the SRID is provided when creating the GEOMETRY object or by calling ST_SETSRID, the SRID is 0.

ST_SETSRID()

Returns a GEOMETRY object that has its SRID set to the specified value.

Use this function to change the SRID without affecting the coordinates of the object. If you also need to change the coordinates to match the new SRS, use ST_TRANSFORM instead.

ST_TRANSFORM()

Converts a GEOMETRY object from one spatial reference system SRS to another.

Use this function to change the SRID and the coordinates of the object to match the new SRS (spatial reference system).

If you just need to change the SRID without changing the coordinates (e.g. if the SRID was incorrect), use ST_SETSRID instead.

Syntax

ST_SETSRID( <geometry_expression> , <srid> )

Examples

The following example creates and returns a GEOMETRY object that uses the SRID 4326:

ALTER SESSION SET GEOMETRY_OUTPUT_FORMAT='EWKT';

SELECT ST_SETSRID(TO_GEOMETRY('POINT(13 51)'), 4326);

Syntax

ST_TRANSFORM( <geometry_expression> [ , <from_srid> ] , <to_srid> );

Examples
The following example transforms a POINT GEOMETRY object from EPSG:32633 (WGS 84 / UTM zone 33N) to EPSG:3857 (Web Mercator).

-- Set the output format to EWKT

ALTER SESSION SET GEOMETRY_OUTPUT_FORMAT='EWKT';

SELECT

ST_TRANSFORM(

ST_GEOMFROMWKT('POINT(389866.35 5819003.03)', 32633),

3857

) AS transformed_geom;

After setting the SRID on a GEOMETRY object, you can check if it has been applied correctly using the ST_SRID() function.

ST_SRID()

Returns the SRID (spatial reference system identifier) of a GEOGRAPHY or GEOMETRY object.

Currently, for any value of the GEOGRAPHY type, only SRID 4326 is supported and is returned.

Syntax

ST_SRID( <geography_or_geometry_expression> )

Examples
This shows a simple use of the ST_SRID function:

SELECT ST_SRID(ST_MAKEPOINT(37.5, 45.5)); +-----------------------------------+ | ST_SRID(ST_MAKEPOINT(37.5, 45.5)) | |-----------------------------------| | 4326 |
+———————————–+

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

Oct 12, 2023 | Data Domain, Technology Application

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
USES	A CRS is used to represent the location of a point on the Earth's surface	A geodetic datum is used to define the shape and size of the Earth's surface and the reference point used to measure positions
PRIMARY FOCUS	A CRS deals primarily with coordinate system	A geodetic datum deals with the underlying shape and size of the Earth's reference ellipsoid
DEFINITIONS	CRS definitions typically remain consistent	Geodetic datums may evolve over time due to improvements in measurement techniques and advancements in geodesy
OPTIONS	Multiple CRS are available	Multiple 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

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.

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.

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;

TL;DR

Coordinate Reference System (CRS)

What is a CRS used for?

Different Types of CRS

Practical applications of CRS in property and real estate

Read more from The Proptech Cloud

TL;DR

Overview

Coordinate Reference System

Spatial Reference System Identifier (SRID)

Key Points

What are the benefits of setting SRID in Snowflake?

How to set CRS and SRID in Snowflake

ST_SETSRID()

ST_TRANSFORM()

Syntax

Syntax

ST_SRID()

Syntax

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Read more from The Proptech Cloud

Coordinate Reference System (CRS)

Geodetic Datum

What’s the difference?

The main differences between Coordinate Reference Systems and Geodetic Datums

The decision between which CRS or geodetic datum to use

Geographic Region

Application

Desired Level of Accuracy

Practical uses for CRS and geodetic datums

How to set these in Snowflake

Read more from The Proptech Cloud

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