A GIS (Geographic Information Systems) is an interoperable system of software, hardware, and users that aims to capture, analyze, store, query, and represent geographic information in digital media. A CAD (Computer-Aided Design) is a system of hardware and software used by users to create or design objects.
In simple terms, a GIS can be related to maps and a CAD can be related to objects. In other words, to represent a road or set of rivers a GIS must be used, but to design a screw or bridge a CAD is required.
The main differences between a GIS or a CAD are analyzed as follows:
- A GIS necessarily requires a spatial reference, whereas a CAD can dispense with it.
- In a GIS scale change is very simple, in a CAD scale change can be problematic.
- A GIS data is stored in multiple files, while a CAD data can be stored in a single file.
- GIS applications usually use a common terminology (for example, a layer is the same in ArcGIS, QGIS, Erdas, Envi), in a CAD some terms may conflict (for example, a layer in AutoCAD is understood as a layer, but MicroStation understands it as a level).
- In a GIS, analysis predominates, a CAD places greater emphasis on detail and precision (for example, the design of park elements).
- A GIS is very efficient for managing databases, but it is not a strength of a CAD.
- In a GIS, lines or polygons are representations of their associated data, whereas in a CAD the lines and polygons are of paramount importance, because they can be used to represent a plane.
- A GIS represents the real world, a CAD can represent existing or non-existent objects of the real world (design and creativity are dominant).
Both systems can be used together, all depends on what the user needs to do to choose one or the other system. Personally, if I’m going to make the plans of my house or neighborhood I use a CAD, but to make the base map of my city I would opt for a GIS.
Before deciding on a system, it should be taken into account that the skills of a CAD are for objects and those of a GIS for maps.