Coordinate Systems & Projections
What is a Coordinate Reference System (CRS)? A coordinate reference system (CRS) is a coordinate-based reference framework that is used to represent and identify geographical locations on the Earth’s surface. At its core, a CRS consists of a datum, a coordinate system, and a map projection. The datum provides a reference point relative to the…
Understanding Coordinate Reference Systems A Coordinate Reference System (CRS) defines the coordinate system and map projection used to represent geographic data in QGIS. It is critical to properly manage CRS in QGIS projects to ensure accurate analysis and prevent errors due to mismatched CRS between layers. Common issues caused by mismatched CRS include inaccurate distance…
Mismatching CRS Causing Display Issues Geographic information systems (GIS) rely on coordinate reference systems (CRS) to accurately display locations and geometries of geospatial data layers. When loading multiple GIS data layers into a QGIS project, the layers may have differing original CRS assigned to them. This CRS mismatch can cause various display issues: Layers not…
What are Coordinate Reference Systems and Why They Matter A coordinate reference system (CRS) is a fundamental component of geographic information systems (GIS) that defines the coordinate system and map projection used to represent the locations and shapes of spatial features on the Earth’s surface. At its core, a CRS provides a reference framework for…
Understanding Geographic Coordinates Latitude and Longitude Latitude and longitude are geographic coordinates that specify locations on the Earth’s surface. Latitude measures angular distance north or south from the equator, while longitude measures east-west angular distance from the prime meridian. Pairs of latitude and longitude coordinates pinpoint unique locations and are defined in reference to Earth’s…
Understanding EPSG 4326 and 3857 EPSG 4326 – Geographic coordinate system using latitude and longitude EPSG 4326, also known as WGS 84, is a geographic coordinate reference system (CRS) that uses a latitude and longitude spatial grid to define two-dimensional positions on the Earth’s surface. Latitude measures north-south positions ranging from -90 to 90 degrees,…
What’s Not Working With Cylindrical Projections in QGIS QGIS relies on the PROJ library for coordinate reference system transformations and map projections. While PROJ supports many different projections, its implementation of cylindrical projections has some key limitations that can lead to inaccuracies and errors in QGIS. Common Errors and Inaccuracies When adding layers or changing…
Understanding Coordinate Reference Systems A coordinate reference system (CRS) is a method of associating numerical coordinates with positions on the surface of the Earth. It provides a common framework for defining locations so that spatial data layers can be overlaid and integrated accurately in a geographic information system (GIS). There are two main types of…
Understanding Coordinate Reference Systems A coordinate reference system (CRS) defines the translation between a location on the Earth’s surface and its representation on a two-dimensional map. Defining an accurate CRS is crucial for performing precise geospatial analysis in geographic information systems (GIS) software. QGIS supports a wide range of CRS options to match the appropriate…
The Problem of Mismatched Coordinate Systems A key issue that arises when analyzing spatial data from different sources is that the layers may not share a common coordinate reference system (CRS). For example, one layer could be in a geographic CRS using latitude and longitude, while another is in a projected CRS using metric units….