Contents


Introduction

After a long time, I investigated recent developments of GIS and CAD software and I was not surprised that they are somehow are converging to some extent. On the other hand, they are still very separated and when you work in the field of geotechnical engineering and geohazards you must switch between them constantly or enjoy the struggle of half-functioning plugins for GIS and CAD to enable the other. Hence, somehow it is still a giant pain in the ass ;-).

You may stumble into old publications such as by Newell and Sancha (1990) in Computer-Aided Design 22(3), 131 -135 on the differences of CAD and GIS as well as ESRI (the company behind ArcGIS) may want to educate you that CAD and GIS are complementary technologies.

But let us have a look at the USACE EM-1110-1-2909. It defines something called Enterprise Geospatial Engineering System (EGES) where the following areas are considered as geospatial:

  • Surveying and cartography/mapping
  • Remote Sensing (which is more than airborne/satellite mounted LiDAR, RADAR & cameras)
  • Global navigation satellite systems (e.g. GPS)
  • Geographic Information Systems (GIS)
  • Civil Information Modeling (CIM)
  • Building Information Modeling (BIM)
  • Computer-Aided Facilities Management (CAFM)
  • Computer-Aided Design

Let us only focus on CAD and GIS, because depending on required geometric properties (projection) we can sort all of the above to one of these two categories.

The key differences between both are scale and precision. CAD is mostly associated with high precision points, lines, areas (faces) and volumes in 3D Cartesian space without curvature/deformation of the space. In contrast, GIS is mainly associated with large scale low-precision points, lines, polygons and sometimes volumes (blocks) in projected spaces.

Real Applications

CAD for CAE and CAM

The usage of CAD makes only sense if it is seamlessly integrated with numerical simulations, optimization of designs and finally manufacturing/construction. These subfields are called Computer-Aided Engineering (CAE) and Computer-Aided Manufacturing (CAM). We may add Plant lifecycle management (PLM) to this as well. This sounds reasonable and logical. However, I personally met engineering teams that did not used an integrated engineering process but managed to create a ton of errors because they transferred data by hand at the interfaces of these processes.

GIS for Geospatial Analysis

GIS itself basically stores and displays georeferenced data. Besides displaying data as (interactive) maps the real application is performing geospatial analysis.
In most cases the analysis could be performed on a database level (e.g. with POSTGIS) or using simple but sophisticated software for it. SAGA-GIS certainly is an example of a tool that is made exactly for (automated) geospatial analysis. In most cases people build models manually. The results can lead to further engineering work that require CAD.

Traditional CAD and GIS Combinations

The “traditional” combination of CAD and GIS can be summed up like this:

  • displaying 3D structures in GIS
  • displaying maps/satellite images in CAD

This does not make much sense in my opinion. Whenever you do serious analysis you end up having results of one to be inputs of the other. Simply displaying information and solving the rest by converting them from filetype to filetype does not lead to a smooth process and allows for additional mistakes.

Personal Rant on GIS and CAD

There are some applications on the edge of geosciences and engineering where you have to switch between both systems to avoid additional work. This is true especially for applications in geohazards analysis and mitigation. But it is a giant pain in the ass to switch between both all the time and iterate through a parameter space.

Merging FreeCAD with QGIS?

Is there anybody out there interested in merging FreeCAD and QGIS (and perhaps add Blenders rendering engine for beautiful and more important realistic presentations). Usually, I prefer the UNIX/Linux approach of “one tool per task”. In this case it would be some kind of a UI that allows us to call any function we want to an process the input. Combining beautiful and precise drawing capabilities in a 3D orthogonal coordinate system integrated into a real-world GIS. I suggest to keep both raw CAD data as well as GIS data but allow for smooth transitions between them.