Different Coordinate Systems In GIS: Geographic vs Projected

Coordinate systems are a fundamental part of GIS – they represent geographic locations and spatial relationships. But what are these different coordinate systems in GIS? How do they differ, and why would you need them? 

Read on for more insight into this topic!

The Foundation: Coordinate Systems

Let’s start by reviewing the core of geographic mapping, known as coordinate systems. A coordinate system represents locations on a map. It can also be defined as a system that clearly specifies two or more points on a plane. 

This ability to assign spatial points to an object or location in space is crucial in mapping. Furthermore, it can be used to track and diagram the movement of objects.

Cartographers and GIS utilizers rely on geographic and projected systems to make accurate maps, which we’ll dive into more shortly.

The Difference Between Datum and Coordinate System

Another term to be familiar with in the Coordinate System realm is datum. A datum is a specific point in space that is used as the reference point for all other coordinates. Coordinates are measured from this reference point and can be represented in various ways, including degrees, minutes, seconds, and radians.

Datums are the foundation of coordinate systems. Coordinate systems are used to describe the position of objects in three-dimensional space. 

Types of Coordinate Reference Systems

Now that we’ve reviewed the basics of coordinate systems, we can hone in on the intricacies of geographic and projected coordinate systems.

The pivotal takeaway information about the two different systems are:

• Geographic coordinate systems tell us where something is located on earth. Geographic coordinate systems are based on the three-dimensional location of objects in a given space. For example, you might use latitude and longitude to represent locations on a global map.
• Projected coordinate systems tell us how to draw something on a flat surface like a map or computer screen, even though the earth is round. Projected coordinate systems are two-dimensional data projections based on a model of the Earth’s surface. For example, you might use UTM or NAD83 to represent locations on a map.

Geographic Coordinate Systems

A geographic coordinate system is a coordinate system that is based on the Earth’s surface. Geographical coordinates are measured in latitude and longitude and can be represented in a variety of formats, including degrees (°), minutes (′), and seconds (″).

Strengths of Using Geographic Coordinate Systems

Accuracy: A GCS is more accurate because it uses true north as the fundamental reference point. Other systems, such as projected coordinate systems, rely on mathematical formulas to depict or model spatial points as it is on the Earth’s surface. These formulas can be compromised, resulting in incorrect coordinates. 

Reliability: A GCS is more reliable because it is based on real-world measurements. Other coordinate systems, such as projected coordinate systems, are based on assumptions and calculations. If those assumptions or calculations change, those systems’ results can also change.  

Ease of use: It’s easier to understand and use because street addresses are based on latitude and longitude coordinates. Projected coordinate systems may use global positioning system (GPS) coordinates, which do not correspond well to points on the ground outdoors. 

Auditability: A GCS also includes a reference line that tracks changes in geographic locations, enabling users to assess data accuracy or changes over time.

Projected Coordinate Systems

Projected coordinate systems are representations of the Earth’s surface that are not based on a physical projection. Instead, they are created by projecting a coordinate system onto a plane or surface that is not itself located on the Earth’s surface. 

This allows for great flexibility when working with maps and coordinates.

Strengths of Using Projected Coordinate Systems

-Accuracy can be enhanced. While GCS can be more accurate than PCS, proper calibration of the projection formula/algorithm can improve its accuracy in mapping.

-More efficiency. A PCS is easier and more convenient in creating maps because they consider the curvature of the Earth’s surface. 

-Can be used to create 3D maps.

Other Tidbits to Know

It’s important to understand the coordinate system you’re using when working with GIS data. Misusing coordinate systems can lead to inaccurate mapping and erroneous interpretations of data.

An object’s coordinates can be determined on a map by simply looking up its longitude and latitude values. A Global Positioning System (GPS) can also be used to determine an object or location’s coordinates in a given space.

In the case of unmapped locations or objects without a GPS, a preliminary survey is required to capture the entire area being mapped, and the corresponding spatial points can be generated from this data. This can be done through land surveys, aerial or satellite imaging, or basic triangulation.

For our work creating maps of indoor spaces, Maptelligent creates digital twins to show users a real-time, interactive map of their buildings. 

Geographic vs. Projected Coordinate System: The Verdict

Each system excels for different uses, and both help expand and improve GIS mapping. 

On the one hand, a projected coordinate system is more efficient and easier to work with when mapping objects in space. On the other, a geographic coordinate system is integral in determining the exact spatial point of an object or location in space.

GCS provides the necessary spatial data, while PCS is essential in mapping or projecting the spatial data in a way that’s easy to understand and apply in real life. 

An effective mapping solution, like Maptelligent, integrates the two systems, resulting in an accurate and comprehensive overview of a building. Our indoor mapping programs help our clients get clear and detailed information about their buildings, and the items and people inside them.

Final Thoughts

Geographic and projected coordinate systems are integral to accurately and effectively map any object or location in a given space.

At Maptelligent, our engineers use both systems and adapt them to focus on individual building mapping. By doing so, we create highly accurate indoor maps that can increase efficiency & safety and help your business thrive.

To see how intelligent mapping could benefit you, contact us for a demo from Maptelligent!