Coordinate Systems & Projections
Why Area Measurements Change with Coordinate Systems A map projection is a systematic transformation of the latitudes and longitudes of locations on the surface of a sphere or ellipsoid into locations on a plane. This process inevitably introduces distortions in shape, area, distance and direction as the three-dimensional Earth is transformed into a two-dimensional map….
Understanding Coordinate Reference Systems A coordinate reference system (CRS) is a method of associating numerical coordinates with a position on the Earth’s surface to enable map projections and spatial analysis. Defining an appropriate CRS is essential for accurate mapping and analysis in geographic information systems (GIS) software. Defining coordinate reference systems A CRS is defined…
What is a Coordinate System and Why it Matters A coordinate system is a reference framework that is used to represent locations on the Earth’s surface. It typically consists of a set of numbers that identify horizontal and vertical positions, allowing the description of spatial information in two or three dimensions. Being able to correctly…
Understanding Earth’s Complex Shape The Earth’s shape is complex and irregular, making the task of mapping its surface a significant challenge. At a basic level, the Earth can be approximated as an oblate spheroid or ellipsoid, bulging at the equator and flattened at the poles. However, the true figure of the Earth, known as the…
Deciding Between Spherical and Ellipsoidal Models Choosing the appropriate coordinate system model is a critical decision when working with geographic data. The two main options are spherical and ellipsoidal models. Spherical models represent the Earth as a perfect sphere, which simplifies calculations but decreases accuracy. Ellipsoidal models account for the oblate spheroid shape of Earth,…
Defining Coordinate Reference Systems A coordinate reference system (CRS) defines the coordinate system and map projection used to represent geographic data in two-dimensional space. Understanding CRS is crucial for performing accurate geospatial analysis in geographic information systems (GIS) software like QGIS. Understanding map projections A map projection flattens the three-dimensional Earth into a two-dimensional map….
The Core Problem of Raster Reprojection When working with raster datasets in Geographic Information Systems (GIS), users often need to reproject data from one coordinate system to another. This allows the raster to be viewed, analyzed, and integrated properly with other geospatial data layers that may have different projections. However, directly reprojecting a raster can…
Understanding Coordinate Reference Systems A coordinate reference system (CRS) is a coordinate-based mapping system that specifies locations on the Earth. It defines a specific map projection, as well as transformations between different spatial references. Common issues that arise when working with unknown CRSs include inability to identify the projection parameters, improper handling of datum transformations,…
The Problem with Unspecified Coordinate Systems Shapefiles store geometric data like points, lines, and polygons as coordinates in an unspecified coordinate reference system by default. Without a defined projection or coordinate system, the coordinates are ambiguous and prone to misinterpretation. Using shapefiles with unspecified coordinate systems can lead to inaccurate data integration, analysis, and mapping….
Understanding Map Projections and Coordinate Systems A coordinate system allows us to assign real-world coordinates to locations on a map. It is crucial for accurately displaying, analyzing, and integrating spatial data in a GIS application. At its core, a coordinate system consists of a map projection and a datum. The map projection translates the earth’s…
