Livin in an alignment Sheet-Less World
The Problem with Alignment Sheets
Now there are a few downsides to alignment sheets, of which we are all aware. Probably the
biggest challenge is keeping them up-to-date in the hands of the people that use them. In the
past twenty years, CAD has replaced manual drafting and now some companies are storing
this information in a database and generating alignment sheets automatically. Updating,
printing and distributing alignment sheets can be expensive. And while automatic alignment
sheet generation is appealing, it is expensive to get the data into a database that is suitable for
automation.
Another problem with paper alignment sheets is that they are a map-report and not a
database. Paper cannot be queried or searched. If sheets are edited, those changes may not be
sent back to a master database or shared with other users; if they are it may take too long. All
too often alignment sheets become notepads for important information that is lost when the
sheet is replaced. In addition, adding new information bands or reformatting manual or CAD
alignment sheets can be prohibitively labor intensive and expensive.
Importantly, if the underlying data is not in a database, the alignment sheets themselves are
the database—a paper or CAD database. But data on an alignment sheet database cannot be
queried, analyzed or integrated with other databases. Rules cannot be established or data selfvalidated.
The data itself is segmented and not centralized and is not really very usable –
unless all you need is the paper.
Terminology
Now is a good time to define a few terms.
Paper alignment sheets are usually thought of as
being only on paper or mylar and are updated with pen and eraser.
CAD alignment sheets are
produced by using a CAD package such as AutoCAD or MicroStation. They are updated by
the user of the CAD software and are plotted.
Scanned alignment sheets are pictures of
sheets that are usually not very suitable for editing. An
electronic paper alignment sheet
would include formats such as Adobe PDF that are also not usually suitable for editing. An
electronic or
digital alignment sheet would include everything except paper. An automatic
sheet generator will normally produce
CAD or
electronic paper output.
Data in a GIS is either vector or raster. Vector data includes points, lines, polygons and text
graphics. Raster data includes photography and other scanned imagery. GIS data is always in
its (approximately) correct geographic location in real world coordinates. CAD sheets may or
may not be georeferenced.
Automating Alignment Sheet
Users of alignment sheet generation software know that automatically generated sheets do
not have the same appearance or detail that CAD or manually drawn sheets have. Automated
sheets usually have predefined bands to better accommodate white space management and
improve appearance. They look more uniform and less cluttered than most drafted CAD
sheets. Since they are a report out of the database, they tend to look more report-like.
Because of this they often lack the level of detail that can be drawn by a human.
A key point that is often overlooked is that the big advantage of automating alignment sheets
is really not in automating alignment sheets itself. It is the process of collecting the
underlying data, organizing and inputting it into the database or GIS that is important. Once
the data is in a database structure that can be readily accessed, many reports (and paper) can
be produced – including alignment sheets.
The four key ingredients for successful sheet generation are first, good quality data, second,
good basemap data, third, good centerline location, and fourth, a good data structure for
storing and retrieving that information.
These ingredients provide a foundation for potentially evolving into a new generation of GIS
and technological toys that may eventually obviate the need for alignment sheets. And just as
users adapt to format changes between manually drawn alignment sheets and automatically
generated sheets, users will adapt to changes in presentation of alignment sheets as we move
forward.
It would appear that we are on an evolutionary path from manual to CAD alignment sheets,
and then on to automated alignment sheets. Over time the data is becoming more centralized
better structured and more integrated. In a few years it will be clear what the next step is, or
will it?
