PSAD56 (EPSG:4248)
Jul 29,2026

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Introduction

PSAD56 (EPSG:4248) is the Provisional South American Datum of 1956, a traditional map coordinate system widely used in South America. Established based on local ground survey data, it was primarily employed for early surveying, cartography, and geographic data collection across South American countries. It utilizes specific ellipsoid parameters and continues to be used in many historical geographic datasets, legacy maps, and routine regional surveys.

Coordinate System Composition

Datum Name & Code: Officially named "Provisional South American Datum 1956," with EPSG code 4248, representing a region‑specific geographic coordinate system.
Reference Ellipsoid: Adopts the Hayford 1910 (International Ellipsoid) as the reference ellipsoid, defining the shape and scale parameters of the Earth.
Geodetic Origin: Uses the La Campana point in Peru as the fundamental origin of the datum.
Projection Type: A geographic coordinate system (latitude/longitude system) without an inherent map projection; it represents point coordinates in degrees of latitude and longitude and is typically used in conjunction with projections such as Transverse Mercator or Lambert.
Vertical Datum: Uses the mean sea level of the South American region as the vertical reference surface, forming a unified horizontal and vertical coordinate system.

Pros

Well suited to the region: As a datum designed specifically for South America, it was tailored to the geological structure and geographic characteristics of the region and met the basic needs of surveying and map production.
Historically important and widely used: From the mid-20th century to the early 21st century, it was widely used for geographic data collection and analysis in South America, providing a foundation for regional geographic studies.
Simple technical implementation: Based on classical surveying methods, it had a relatively low technical barrier and could be introduced and used quickly even in countries with limited resources.

Cons

Noticeable local distortion: At the time, available technology could not properly model local deformation caused by crustal movement and plate activity across South America, so coordinate transformations could introduce systematic errors and make it unsuitable for high-precision geospatial use.
Poor compatibility with modern geocentric systems: With the development of GPS and geocentric datums such as SIRGAS95, PSAD56 became less compatible with modern reference systems and harder to use.
Limited accuracy: Constraints in surveying methods and data processing at the time made it insufficient for high-precision applications such as urban planning and disaster monitoring.
Limited geographic scope: It was designed for South America, so it is difficult to apply on other continents or at a global scale, which limits cross-regional geospatial integration.

Application Scenario

PSAD56 has been widely used in South America for basic surveying and map publishing, providing a consistent coordinate framework for topographic maps and resource distribution maps. It has also supported traditional geographic data collection in areas such as geological exploration and land-use planning, and has served as a spatial reference base for resource management and infrastructure construction. In addition, it has been used as a regional reference standard in early remote-sensing image processing and GIS data integration.