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Geographic Information Systems (GIS)


Overview


The following resources will help you get started with understanding how geospatial data formats, coordinate reference systems, and map projections impact the mapping process.


Geospatial Data Formats



Datums


Datums are an essential component of every mapping project since they provide a standard reference point for measuring surface distances on the Earth. Horizontal datums provide an reference origin point (0,0) for latitude/longitude lines (in relation to a reference ellipsoid). Vertical datums provide a standard reference point (e.g., mean sea level) for measuring elevations . 
 

When you are working on GIS projects, you will need to pay attention to the datum(s) of existing data sets since using data with different datums can impact your analysis and how your data lines up on your map. If you are working with data sets that are based off of different datums, you'll need to use some of the built-in tools in ArcGIS Pro to convert all of your data to a common datum. 

The following resources provide a helpful overview of horizontal and vertical datums and why they're important for GIS:


Learn more about datums



Coordinate Reference Systems and Map Projections


A datum is one component of a coordinate reference system. A coordinate reference system helps GIS software like ArcGIS Pro interpret your data by telling the software where your data is located in the world and how to display your data on a flat surface like a map.

Geographic coordinate systems tell the software where in the world specific features are located via latitude / longitude coordinates. The measurement units are angular (e.g., degrees). Projected coordinate systems tell GIS software how to take the geographic coordinate information and represent it on a flat surface like a map using specific measurement units, directives for how to center the data, etc. The measurement units for projected coordinate systems are usually linear (e.g., meters). Since there's no way to flatten the Earth without some form of distortion, this is where map projections come into play.

Check out the following resources to get a quick intro to map projections and how to determine which map projection(s) are suitable for your study area and analyses.  

 


Learn more about Coordinate Reference Systems



Learn more about Map Projections



Cartography



GIS Dictionaries