PDF Mapping – Michael Bufkin - Adobe Acrobat and PDF for Architecture, Engineering, and Construction - page 202

Source Data
The first issue to consider is the map's source data. Most maps today are derived from GIS, some of which
output directly to PDF. These maps are typically based on a projection and datum which produces at least a
base image that is cartographically correct.
Other maps may be made from CAD systems which utilize a set of graphic elements which may or may
not have been projected to a Cartesian system before being brought into the CAD environment. Some map
source data may simply be scanned images of a paper map, or a satellite image or an aerial photograph
georectified to conform to a projection.
Obviously, the quality and type of data will dramatically affect the accuracy and quality of the output
map.
File Size
In selecting PDF as a publishing format, one must immediately consider the matter of file size. In general,
PDF files are intended to be mobile. They may be made available for users to copy, download, and
distribute on CD.
Very large files discourage ease of downloading and distribution. An informal study has shown that
10MB is roughly the maximum file size that people will accept for downloading from the Web. If you want
your maps to be used, consider techniques for minimizing file size.
Short of reducing the number of features or the paper size of the map, the two ways to reduce file size
are through changes in resolution and compression.
Managing Color and Printing
Another issue of significance in building PDF maps is the handling of color. Different printers may print
the same colors differently. In order to have your map display a consistent appearance when printed, it is
important to define the colors in the PDF carefully. In particular, if the map is expected to be used for on-
demand printing, then color fidelity is extremely important and may require the use of the full capability of
Acrobat color management. This may be further complicated by the presence of imagery data, such as
satellite data, aerial photographs, or scanned images.
The general issue of printing of maps in PDF form can sometimes be thorny. The use of special fonts
can create printing problems, as well as legal issues of font ownership. For maps utilizing PDF layers, it is
particularly important to consider the effect of default print settings, as well as the ability of the user to
print a map with layer combinations not intended by the author.
PDF Layering
PDF layering is a powerful capability for simplifying the user interface. In particular, layer control by zoom
level can significantly improve the display speed of large, highly detailed maps. But it also introduces the
possibility of abuse, particularly for documents which may be used in applications which may have legal
implications, such as navigation and construction.
Using Metadata
An often overlooked issue of PDF map production is that of metadata. Paper maps may usually include
some metadata in the map legend, such as scale, projection, datum, source and date. Electronic maps can
carry much more metadata because it takes up no space on the map display. PDF allows an essentially
unlimited amount of metadata to be included in the document, and to the extent possible this should be
exploited.