What is a Gantt Chart?
Is Gantt Chart same as a Scheduling Bar Chart?
What is a Time Scaled Logic Diagram? Is it same as Gantt chart?
What is a Time Scaled Network Diagram? How is it different from Gantt Chart?
Project Schedule can be represented in many ways. In one of my previous articles, on Project Schedule Network Diagrams, I outlined 4 ways for drawing Project Schedule. I have written this article to describe Scheduling Bar Chart. Scheduling Bar Chart is simply called Bar Chart. Bar chart is one of the most popular ways to pictorially represent Project Schedule. The other 3 ways to draw Project Schedule are:
- Project Schedule Network Diagrams
- Milestone Charts
- Project Calendars
So, what is a Gantt Chart?
Bar Chart is popularly known as Gantt Chart. The name is attributed to Mr. Henry Gantt who extensively used them in his work. Some Project Managers believe that he was the creator of Bar chart and hence the name. While others believe that Bar Charts were used by Planners even before Mr. Henry Gantt. History of Bar Charts is an interesting topic but I will leave it for another day. In this article I will use “Bar Chart” to mean “Gantt Chart” for those who are more familiar with the latter term.
What is a Bar Chart?
A Bart Chart is a 2-dimensional chart. Schedule Activities or WBS Components are represented as Horizontal bars in a Bar Chart.
- Vertical Axis is used for listing Schedule Activities or WBS Components. Usually left side is used for listing.
- Horizontal Axis is used as a time scale. It shows Activity Start & Finish dates.
- The length of bar represents activity duration. The duration can be shown in any time unit e.g. hours, days, weeks, months etc.
- Different colored bars are used to show finished and unfinished work. Usually finished portion of an activity is shown in dark color. Usually unfinished portion of an activity is shown in White or light color.
- A summary Activity is also shown as a Bar. Usually, Summary Bars have different color and/or shape than regular Bars.
- A milestone is generally shown as small rhombus.
You can also look at Max Wideman’s Glossary for some other definitions of Bar Chart.
Example of a Bar Chart
What is a Time Scaled Logic Diagram?
A Time Scaled Logic Diagram is a form of Bar Chart in which Project Dependencies are shown by using arrows. Two related Activities are joined by a unidirectional Arrow. Arrow Tail represents the Predecessor. Arrow Head represents the Successor. These diagrams are also called Time Scaled Network Diagrams. These Diagrams are a cross between traditional Bar Charts and Network Diagrams.
All Bar Charts are popularly known as Gantt Charts. A Time Scaled Logic Diagram can be used to draw 4 types of logical relationships: