The advantage of merging CAD and GIS

The advantage of merging CAD and GIS

David Lankford
CADTEL Systems, Inc
11201 North Tatum Blvd., Ste. 200
Phoenix, AZ 85028

Introduction
Computer Aided Drafting (CAD) software has been used as a tool for engineering design for many industries, including electrical, mechanical, architectural, as well as telecommunication companies. Its primary use in telephone has been drawing and maintaining outside plant maps.

Geographic Information Systems (GIS) have developed in the areas of environmental impact studies, demographics, city planning and land surveys. Some telecommunication companies have begun using it for planning, forecasting, routing and cellular propagation. Although GIS and CAD have evolved independently, each serving a different purpose, the convergence of the two technologies is a natural fit for the telecommunications industry and the only hope for the ultimate enterprise-wide database solution. Every company has wanted this, but few have achieved it.

The advantages of bringing the two technologies together are countless. The biggest obstacles are changing some of the traditional processes that were used with paper maps and learning how to use digital data efficiently. If the focus is on compatibility and standardization, the two software paradigms will draw increasingly toward one another.

The advantage of using CAD in a GIS
CAD is an indispensable tool in the engineering and design process. Outside Plant (OSP) engineers prefer CAD to GIS because rather than working with raster data they use vectors, lines with known X and Y coordinates and exact lengths. Symbology, as well as rotation angles, are very important in engineering. Equally important is the ability to manipulate graphic elements. These and other drafting functions are more native to CAD than to GIS. The CAD environment makes greater use of the mathematical model and allows an engineer to store his drawing and return at a later time to complete or revise it. This works much the same way as editing a letter in a word processor. In a sense, while GIS deals with the world and facilities as they exist now, CAD creates a proposed "new" world and is the preferred design tool of the engineer.

It's clear that CAD and GIS differ in function and application, and it is also clear that CAD and GIS users differ in the ways they use that same data. As a result, each represents the same data set differently internally and often graphically. For example, the engineering department uses CAD and may represent the 50' road as being 400' wide. This is to allow room on the drawing for facilities, symbology and annotation. The other departments in the organization can not use the CAD drawing because it is not drawn to true scale.

As a result, other departments that use the GIS, such as marketing and planning, have to build, maintain and endure the cost of duplicate sets of data to serve their specific needs. In order to implement an enterprise-wide database that will serve the needs of the entire company, it will be necessary to have data that is compatible with CAD and GIS applications alike.

The graphics engine provided by a CAD package, combined with the database query capabilities of a GIS, produces the tool that engineers have only dreamed of for years. Some of the benefits of an integrated CAD and GIS system are:

The CAD interface is familiar and comfortable to use, yet provides the sophisticated fimctionality of a GIS.
Drawings are generated from a seamless database. That means that there are no more breaks in the data or scale changes. Data can be queried, completely or partially, then stored in a CAD drawing file to work on at a later time.
Every line or symbol in the drawing has an intelligent link to the database, providing cable counts, joint-use information, customer information, street names and addresses, as well as cost and inventory information.
Text templates allow the user to select which attributes to use when annotating facilities in the drawing. This selection can be made from a large number of fields in the database. Text templates can be used while doing a query to annotate facilities automatically, or each facility can be annotated individually.
From the same data sets, queries can generate either graphical reports or textual reports,
A working drawing or project can take weeks and may require many changes before the design is complete. So all proposed facilities and changes to existing facilities will stay in the drawing until the job is "pre-posted" to the database.
When a job is pre-posted to the database, everyone on the network with appropriate security access, can see the changes and additions and each can have simultaneous access to all database information.

How a GIS creates an enterprise network model
The strength of a GIS is its ability to enter, retrieve, analyze, store and output spatial data. Typically, 85'XOof the data in a telecommunications company has a spatial element that can be tied to a geographic location. A GIS will work with vector data from a CAD system, but it also allows the manipulation of giant arrays of integer and floating point raster data. This allows the use of satellite imagery and aerial photos as a landbase, so GIS graphical data representations are not a mathematical model as much as a graphic representation. The capabilities of a GIS system lend more to the decision making process and long-range planning. Ultimately, it deals effectively with the big picture.

For it to be effective, there can be no conversion process back and forth and neither the CAD nor GIS software can have any element that uses a proprietary format, graphical interface or database. If all data (graphics and attributes) are stored in an RDBMS such as Oracle, Sybase or SQL server, and everyone is on the same network, data can flow through the organization from one department to another regardless of the application software being used. This means that demographics purchased and modified by the marketing group with their GIS software can be shared with the engineers who can view the same data with their CAD software.

There is no more duplication of databases with the uncertainty of which one is correct. Current data stored in a common RDBMS that is shared with everyone in the company means increased productivity and better customer service. In addition to the data integrity, numerous applications can access and edit the data simultaneously.

An Example of Integrated CAD and GIS Data

Use the GIS functionality to query the area in which he will be working: landbase, facilities, customers, whatever is appropriate for the task..
Using the CAD functionality, new poles, cable, facilities, customers, landbase elements, etc. can be drawn or placed.
At any point during the design process, when additional information is needed, simply selecting the existing CAD element (a facility) will display all of the attributes in the database pertaining to that individual item (a GIS function).
Data analysis such as terminal status, pair availability, customer assignment, locations of other utilities and any potential conflicts, etc. can be performed without leaving the desk using GIS.
Calculations such as "Loop Make-up" can easily be done with the GIS by retrieving data from the database and then applying mathematical formulas from the CAD to determine the resistance, dB loss, and the distance back to the Central Office.
Bridged tap for a given pair can also be calculated (GIS function). And, if necessary, displayed graphically on the screen to determine its location (CAD function). These functions could not be accomplished on a conventional CAD system because of the limitations of the non-intelligent entities in the drawing; they must be linked to the GIS database.
In addition, all of the facilities placed in CAD drawings can instantly update the Continuing Property Records (CPR), assignment, joint use records and right-of-way data when the work orders are posted "As-Built" in the GIS.

Conclusion
The real key to success is that everyone has access to the data. Low cost viewing tools are readily available that can be customized to allow the user to do his job with little or no training. By creating dozens of application-specific tools and propagating them throughout the company, everyone becomes part of the team to help enter the data that will feed accurate and up-to-date information to the entire organization.

When a company combines the functionality of a CAD and a GIS, the benefits are immediate and far-reaching. The opportunities that this technological merger opens up are endless and limited only by the imagination. Having a set of data utilized by many departments increases data integrity, accuracy and workplace efficiency. This integration will open up new worlds to a company and its customers.