A GIS expert addresses GIS/CAD interchange, interoperability, 3-D modeling, and data accuracy.
GIS and CAD may have developed as distinct technologies, each with its own focus and strengths. But increasingly, the two applications are converging, and together they can provide an effective arsenal of design and analysis tools for civil engineers. Don Kuehne, CAD products manager for GIS developer ESRI, answers some frequently asked questions about the use of GIS in engineering workflows and GIS/CAD interoperability issues.
Q: Why should I care about GIS and CAD interchange?
A: You should care because it helps you do your job. GIS and CAD are not what people do; rather, people work with GIS and CAD as tools to do their jobs. In their jobs, people solve problems, they build things and make life more livable. GIS helps engineers and surveyors make better and more-informed decisions in a profitable and efficient manner, allowing people to better do their jobs. GIS science provides a means to abstract the built and natural environment into a computable collection of centralized and federated information repositories, explicitly defined and inferred. GIS provides the visualization, analysis, and synthesis of this information regardless of how and why it was originally created.
Q: What are the opportunities of using GIS in the engineering workflow?
A: The opportunities are to make better decisions, improve workflows, and multiply the value of data work products through re-purposing. There is an opportunity to leverage GIS for the purpose of making design decisions, as well as an opportunity for the engineer and surveyor to be the primary source of authoritative GIS content. Then they can offer this expertise to stakeholders, who can use the information later in a built asset’s lifecycle, essentially building and supporting asset management systems in the engineering and construction phases.
Q: What are the barriers to overcome when changing from CAD to GIS and vice-versa?
A: There are definitely technical and cultural differences between GIS and CAD technology, but I would encourage people to focus on the similarities between the two and take an objective look at which tools are appropriate for any part of the workflow to help them get their job done. Interoperability is a term that, when used correctly, identifies those aspects of technology that allow people to access the appropriate information and tools in the appropriate environment and does so in a mixed computing environment. The goal of interoperability is not recreating one technology in the foreign and sometimes hostile computing environment of another. Rather, interoperability should be used to describe how information and tools are utilized across GIS and CAD computing environments, accessing the authoritative source of tools and information.
Q: Who benefits from GIS and CAD interoperability?
A: Decision makers and designers benefit the most by interoperability. Those who can define their jobs or tasks as wholly GIS or exclusively CAD drafting are less served by interoperability than those who are making decisions for design or planning based on information that may be created and accessed in one system or another. The pre-design and design phases of any project greatly benefit from interoperability. The same can be said for the as-built and planning phases, which can leverage data that may have been created in GIS or CAD. The designer will have access to the GIS base map, not a CAD copy or paper map. Parcels, soils, survey control, flood planes, and utility infrastructure will all appear inside their design environment, whether it is in GIS or CAD.
If the designer has access to GIS base data such as parcels, soils, utilities, survey control, floodplains, utilities, and topography—and not merely a CAD copy or paper map of the data—he or she will be able to leverage that data through advanced spatial analysis and visualization technology, enabling better decisions and better communications with clients and the public.
Q: Can access to high-quality, interoperable, and better data with integrated decision-making tools improve my design?
A: Perhaps the best answer is a restatement of the question. Does design suffer from the lack of integrated decision-making tools based on low-quality and incompatible data sources? You may have heard it said that sometimes the process is driving innovation when really innovation should be driving the process. By that I mean convention and fear of rocking the boat often contribute to inefficiencies. This drives people to request technology in a form that really doesn’t serve their needs but rather their skewed expectations that are in line with the way we currently do things.
Having access to high-quality interoperability will give you access to more and better data. Using more and better data in the design process will improve your design.
Q: How is GIS involved in doing 3-D modeling in civil engineering software?
A: Foundational to civil design is survey and terrain. Currently, 2.5 data such as terrain, draped features, and 3-D symbols are used to visualize roadways and the landscape. Great strides are being made in 3-D GIS research, which makes this 3-D design data computable in the same way as existing 2-D GIS data. Because GIS is database driven, extremely large amounts of data can be managed. This is particularly important with LiDAR data where, at times, billions of points are collected.
Q: Is building information modeling (BIM) a data standard, design software, or a new technology platform?
A: For many, BIM continues to hold the expectation of an over-arching technology where the building information models and their explicit definitions are the key to making better decisions for an ever-growing and seemingly unlimited list of applications.
I applaud the efforts of various organizations promoting standards and starting conversations that help put scope and context to efforts in the building industry to reduce waste and promote better practices. The standards themselves are not an information system, but they do serve as a powerful means to define the semantics of how to ask better questions and serve as the context for new information systems applications. They challenge the building industry to consider new ways to improve how things are done.
GIS seems to be well positioned to benefit from the efforts of BIM data standards development as another well or poorly structured data source that can benefit from geospatial visualization, computing, and management. If you consider a building can be a geographic feature, then the GIS is a fine BIS—Building Information System—for many existing applications related to site selection, planning, operations, and management of buildings. Assuming you have the tools to read/write and analyze the data for a given information system application, there is nothing special about a building that disqualifies it as just another GIS data set.
Q: Do I need to change how I work to benefit from GIS?
A: Yes and no. A product like the free download ArcGIS for AutoCAD is a great example of how you can benefit from GIS with minimal effort inside CAD. This type of tool is part of a trend where information systems can not only be accessed over the Internet, but also within other computing environments. Instead of adding GIS data files and recreating GIS tools in your CAD system, you can simply use GIS services within my CAD system.
If you make changes to the way you think about your work, it is possible that new workflows and efficiencies can make you more competitive, and result in more valuable work products. In this case, both what you design and the information about that design become assets—one the physical asset, the other a digital asset. Creating CAD data that is more easily repurposed as GIS content can make an investment in small CAD workflow changes pay off down the road as more valuable data work products.
Q: Is it true that using “trusted” CAD flat file storage rather than the more precise GIS database corrupts the accuracy of survey and engineering data?
A: Precision is often confused with accuracy, and although CAD files cannot store coordinates as precisely as the modern GIS data sets, they are generally accepted as sufficient for storing accurate positional information for the coordinate system in which they were recorded.
Generally, there are six types of accuracies in digital maps and in GIS. These can be categorized in other ways and methods such as:
- Accurate feature identification—For example, a valve on a map is in fact a valve in the real world system.
- Temporal—How current is this data? Is the valve still there?
- Attribute accuracy—What type of valve is it? When was it installed?
- Topological accuracy—What is the connectivity of the data? How is the valve connected to the water system?
- Relative accuracy—This is the distance relative to other objects inside or outside the system. How close is the valve to the hydrant?
- Positional accuracy—Is this the correct location?
Today, anyone with access to the Internet can author and use digital maps. This is possible because spatial information can be gathered from multiple virtual locations and represented in a single map display. An environment that provides shared access to digital geographic data is a powerful driver for hosting many software tools that serve a variety of spatial applications. Building maps that draw from these different spatial data sources demands new technologies for accurate integration of this data.
For data to be useful in a database, and reused in many ways, a consideration of all types of accuracy should be understood. Structured data in a database can be used many ways beside creating a visualization such as a drawing, map, globe, rendering, flythrough, et cetera. Detailed analysis such as hydraulic modeling, buffering, or geocoding can be performed on the same data set if properly modeled and managed.
Q: What accuracy of data should I be collecting and using for my project?
A: The accuracy that provides the best results. If I asked the question, “What is the safest design of a bridge?” I have heard an engineer say that the best answer would be to fill the valley with concrete—hardly practical in most situations. It certainly would be safe, but would not likely win any design awards.
Our technology challenge is to recognize our existing data for its accurate elements, and take the best elements from each of these sources, enhancing the overall data accuracy in the final product.
Data should be collected at spatial accuracies and attributes collected that serve the needs for the project. This includes beyond the design phase and into the construction and operation and maintenance (O&M) phases. Seventy-five percent of the cost of infrastructure throughout its life is in the O&M phases, so collecting data in the development phases that is useful in the O&M phases can yield substantial return on investment, not to mention additional services for the engineer and surveyor.
Don Kuehne has 20 years of experience with CAD/GIS/Engineering integration and is currently the CAD products manager for ESRI. He has a degree in civil engineering; work experience in municipal, department of transportation, and consulting engineering; and is a frequent technical presenter on the topics of CAD, BIM, and GIS.