Projection
A mathematical transformation that represents the curved surface of the earth on a flat map, with different projections preserving different properties.
Detailed Definition
A map projection is a systematic mathematical transformation that converts locations from the curved surface of the Earth onto a flat (planar) surface for mapping, analysis, and visualization. All projections introduce some form of distortion.
- Area: The relative sizes of features (equal-area projections preserve area)
- Shape: The form of features (conformal projections preserve shape locally)
- Distance: Measurements between points (equidistant projections preserve distance from certain points)
- Direction: Angular relationships (azimuthal projections preserve direction from a central point)
Common projections in mining and land management
UTM (Universal Transverse Mercator): - Conformal (preserves shape) - Earth divided into 60 zones, each 6 degrees wide - Widely used for topographic mapping and engineering - Good for areas within a single UTM zone
State Plane Coordinate System: - Conformal with minimal distortion - Designed for accurate measurements within each state or zone - Used by surveyors, engineers, and state agencies - Multiple zones per state (based on state geometry)
Albers Equal-Area Conic: - Preserves area (useful for thematic maps) - Used by USGS for maps of the conterminous US - Good for east-west oriented regions
Web Mercator: - Used by web mapping platforms (Google Maps, Bing, OpenStreetMap) - Severely distorts area at high latitudes - Not suitable for area measurements
Selecting a projection: - For mining site engineering: UTM or State Plane - For claim area calculations: Equal-area projection - For web display: Web Mercator - For national-scale maps: Albers Equal-Area or Lambert Conformal Conic
Related Terms
GIS
Geographic Information System - software and technology for capturing, storing, analyzing, and displaying geographically referenced data.
Spatial Data
Data that describes the location, shape, and relationship of geographic features, including vector and raster formats.
Coordinate System
A framework for defining locations on the earth's surface using numbers. Common systems include geographic (lat/lon), UTM, and state plane.
Datum
A reference framework for defining geographic coordinates. NAD83 is the standard horizontal datum in the US for spatial data.