# Understanding Coordinate Reference Systems and Their Impact on Geospatial Data Display

Coordinate reference systems (CRS) provide a framework for defining the position of geographical features on the Earth's surface. They are crucial for ensuring that spatial data is accurately mapped and can be consistently used and interpreted across different GIS applications and platforms. Without a standardized CRS, geospatial data from various sources would not align correctly, leading to errors in mapping and spatial analysis.

Maya uses two different CRS systems: the EPSG:3857 for everything that includes the calculation of a size and the EPSG:4326 for everything else, for example, the presentation of the area of interest and output of data analyses in the reports.

EPSG, which stands for the European Petroleum Survey Group, was formed in the 1980s by oil and gas companies to standardize geodetic parameters, including coordinate systems. Their efforts resulted in the creation of the EPSG Geodetic Parameter Dataset, which cataloged and standardized CRS definitions for use across various industries, extending beyond just petroleum exploration.

- EPSG:3857 was developed by Google for their mapping services in the early 2000s. It has become the de facto standard for web mapping, ensuring compatibility across different platforms and devices such as Google Maps and OpenStreetMap. It uses a so-called Mercator projection to map the Earth on a flat surface.
- EPSG:4326 is a coordinate reference system used by the Global Positioning System (GPS). It is based on the World Geodetic System 1984 (WGS84), which defines the shape of the Earth as an ellipsoid and uses degrees of latitude and longitude to specify locations on the Earth's surface. The ellipsoid assumes a smooth, regular shape, but the real Earth has varying elevations and irregularities, leading to some level of coordinate distortion. These distortions are generally small but can become significant over large distances or in precise surveying and mapping applications.

**Mercator Projection **

The EPSG:3857 uses a so-called Mercator projection that maps the globe onto a flat surface in a way that preserves angles and shapes over small areas but distorts size and area, especially when you move away from the equator. Despite being less precise than EPSG:4326 (which uses an ellipsoid), EPSG:3857 is often used due to its compatibility with various web mapping services and because of its simplified calculations, which enable efficient and fast data processing.

**Area Calculations With EPSG:3857**

To calculate an area size using EPSG:3857, you start by identifying the polygon's coordinates (latitude and longitude). These coordinates are then converted into the CRS system, representing them in meters on a flat map. Using these converted coordinates, the area within the polygon is calculated in square meters and can then be converted into hectares if needed.

As you move away from the equator, the scale factor increases, leading to exaggerated sizes of land masses near the poles. This distortion can result in significant errors in area calculation for large polygons.

**However, this is a totally normal limitation, and you don’t need to worry about it impacting the results of geospatial analyses on Maya using various source datasets. As with both Coordinate Reference Systems, EPSG:3857 and EPSG:4326, the underlying data itself is not distorted; the distortion affects how the data is displayed, or distances are calculated, but not the dataset’s values.**