Coordinate Systems & Projections
Understanding Coordinate Reference Systems A coordinate reference system (CRS) defines how a two- or three-dimensional space is divided into coordinates that allow the positions of points in that space to be uniquely defined. Geographic coordinate systems use latitude and longitude in angular units like degrees while projected coordinate systems use linear units like meters. The…
What are Custom Coordinate Systems? A coordinate system in GIS defines how geographic data is represented on a map. It specifies information about the datum, map projections, units of measurement, and other parameters needed to accurately display locations and geometries. While most GIS software comes with predefined coordinate systems, QGIS allows users to create custom…
Understanding Geospatial Data Processing Workflows Geospatial data processing workflows refer to the end-to-end processes involved in ingesting, transforming, analyzing, and visualizing geospatial data. Key steps often include acquiring raw geospatial data, preprocessing it into appropriate formats, performing spatial analysis, and creating maps, charts, or other visuals to explore the data and communicate insights. Efficient workflows…
Defining Projection Systems Properly A map projection flattens the three-dimensional Earth into a two-dimensional map by mathematically transforming geographic coordinates of latitude, longitude, and elevation into planar coordinates of x, y, and z. Defining map projections properly is crucial for accurate geospatial analysis and visualization. Mistakes in projection definitions can lead to distorted measurements, inaccurate…
Understanding Coordinate Reference Systems A coordinate reference system (CRS) is a coordinate-based reference system that defines locations on the surface of the Earth. It consists of a set of numeric coordinates and parameters that determine how those coordinates relate to positions on the Earth’s surface. Common components of a CRS include a datum, projection, coordinate…
Understanding Coordinate Reference Systems Defining coordinate reference systems A coordinate reference system (CRS) is a method of assigning numerical coordinates to any location on the Earth’s surface to define its absolute or relative position. In GIS, each map layer contains geospatial data that uses a CRS to determine the location of the features. Common CRSs…
Understanding Coordinate Reference Systems A coordinate reference system (CRS) allows locating geographical features on the Earth’s surface by defining a specific coordinate system and map projection. Selecting the appropriate CRS is essential for visualizing, analyzing, and integrating spatial data in QGIS. Definition of a CRS A CRS systematically specifies locations on the Earth using coordinates….
Identifying Unknown Coordinate Systems Examining metadata associated with spatial data is crucial for identifying unknown coordinate reference systems. Metadata often contains information on the coordinate system, projection parameters, datums, and more. If metadata is unavailable or lacks spatial reference details, use the identify tool in GIS software such as ArcGIS to view the feature class…
Overview of 360 Degree Raster Projections 360 degree rasters, also known as panoramic images, are photographic images with a 360 degree field of view horizontally and 180 degree field of view vertically. These wide angle images wrap around the viewer to provide an immersive experience, allowing the viewer to look in any direction just as…
The Problem of Inaccurate Slopes from Projected DEMs Digital elevation models (DEMs) are raster representations of terrain elevations across landscapes. When DEMs developed in native projection systems like geographic coordinates are projected to planar systems like Universal Transverse Mercator (UTM), elevations and slope calculations can become distorted. This distortion occurs because the process of projecting…