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.
