Others are intended to used for reference for decades or centuries. For these reasons, context can influence both the form and content of a map in ways both great and small. Decisions about map design are tempered greatly by source materials themselves, by what is available and how easily it can be communicated. Sometimes our source materials have limitations or are incomplete. They may present special problems of presentation because of technical terminology or because of the quantities of detail required to make a point.
Some data needs to be qualified.
These limitations must be considered from the very start of a project so that they can be addressed in the design of the map. Finally, one must consider the twin questions of how much time to invest in a project and what systems to use, whether manual or automated and, if automated, what type of software. Both questions are, of course, best addressed with experience. However, it is important to realize that production time drops dramatically with practice. Sometimes scholars avoid using maps because of the time expense involved in their production.