Gantt chart(redirected from Gantt charts)
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Gantt chart[′gant ‚chärt]
A graphic device that depicts tasks, machines, personnel, or whatever resources are required to accomplish a job on a calendar-oriented grid. Charts may be provided for various managerial levels and responsibilities, but detailed planning occurs at the lowest organizational level. Performance may be monitored and controlled throughout the organization.
The Gantt chart is an effective tool for planning and scheduling operations involving a minimum of dependencies and interrelationships among the activities. The technique is best applied to activities for which time durations are not difficult to estimate, since there is no provision for treatment of uncertainty. On the other hand, the charts are easy to construct and understand, even though they may contain a great amount of information. In general, the charts are easily maintained provided the task requirements are somewhat static.
An initial step in development of a Gantt chart may be to specify the tasks or activities making up a project, as shown in the illustration. The amount of time required for each activity is represented as a horizontal bar on the chart, with open triangles designating original start and finish dates in this example. The open start triangle is changed to a filled triangle upon inauguration of the activity, and the bar is filled in with vertical lines to indicate progress and completion. The open finish triangle is also filled upon completion. Slippage times are documented on the chart by broken lines, and the diamond symbols are employed to indicate rescheduled work. The vertical line on the chart is the current-date indicator and indicates present and future status of the project as of that date.
Updating of a Gantt chart will reveal difficulties encountered in the conduct of a project. Possible solutions include rescheduling, overtime, multishift operations, use of additional equipment and facilities, and changes in method.
An outgrowth of the bar chart technique is the milestone chart. A milestone is an important activity in the sequence of project completion. The most significant activities may be designated major milestones. The primary difference in this concept is the graphic display, since the method and collection of data are the same. The milestone approach offers no intrinsic improvement over the basic Gantt chart but provides a means for focusing resources on critical items. See PERT