Gantt chart and Scheduling techniques

Abstract

Scheduling is about "determining when an activity should start or end, depending on its (1) duration, (2) predecessor activity (or activities), (3) predecessor relationships, (4) resource availability, and (5) target completion date of the project."

In this article, a review of scheduling techniques will be presented. The Gantt chart one of the oldest scheduling tools and is a graphical way to explain and display the schedule-related information. The tool displays each activity and the duration, and clarify what should have been achieved at a certain point in the time. The limitation with the Gantt chart it that the tool does not show the critical activities, which the Critical path method (CPM) does. The CPM is an algorithm for scheduling a set of project activities in the project. In the CPM a Network diagram needs to be developed. The Network diagram is about identifying the component activities and their relation to each other.
This article will provide a step-by-step guide on how to create and use the different scheduling techniques. Furthermore, this article will explain how the different scheduling techniques can supplement each other, and what the limitations in each scheduling tool are.

Project Time Management

Figure 1: Scheduling overview. Received from:

Project Time Management provides the processes that are required in a project with timely completion. The Project Time Management includes six processes which are described below :

1. Define Activities - Identify the activities and actions to be performed to produce the deliverables of the project.

2. Sequence Activities - Identify and document the connections between the activities in the project.

3. Estimate Activity Resources - Estimate the amounts and types of the material, people, equipment, or supplies needed to perform the activities in the project.

4. Estimate Activity Durations - Approximate the number of work periods required to perform individual activities with the expected resources.

5. Develop Schedule - Analyse the activity durations, sequences, resource requirements, and schedule restrictions to produce the project schedule.

6. Control Schedule - Control the status of the project to update project development and managing the changes in the project schedule.

Scheduling A plan can only show the practicability of accomplishing its objectives when the actions and activities in the plan are put together in a schedule that illustrates when each action or activity will be carried out. Today there is many different methods and approaches to scheduling. It can either be by computer-based planning tools or done manually The scheduling method dictates the procedures and rules for the scheduling process in the project. Tools like Gantt chart and Critical Path Method (CPM) are tools often used in the planning process of a project. By combining the scheduling tool or method and using the outputs from the processes in the Project Time Management; define activities, sequence activities, estimate activity resources, and estimate activity, the project schedule can be produced. Figure 1 describes how the scheduling methodology, scheduling tool, and outputs are interacting with each other and in the end creates the project schedule.

Gantt chart

What is a Gantt chart?

Gantt chart is the oldest form of a formal scheduling tool. The Gantt chart was developed in the 1910s by Henry Gantt, and today used widely as a scheduling tool in projects.

Definition

"A graphic display of schedule-related information. In the typical bar chart, schedule activities or work breakdown structure components are listed down the left side of the chart, dates are shown across the top, and activity durations are shown as date-placed horizontal bars.".

When and why use Gantt chart?

Assess how long a plan should take, lay out the order in which tasks need to bed carried out Manage the dependencies between tasks See what should have been achieved at a certain point in the time See how remedial action may bring the plan back on course

How to create a Gantt chart?

Developing a Gantt chart takes some steps. In the scoping phase determines the level of details and the activities identifies in the project. There are many ways to create a Gantt chart and in the end, it depends on the project and the working style. In the table below are some general steps to developing a Gantt chart described.

How to create a Gantt chart. Received from: [1]

Creating a Gantt chart step by step

Step 1 - Creating the axes: Create a sheet with vertical and horizontal axes. The vertical axis represents the activities, and the horizontal axis represents the timescale. To make the Gantt chart more clear and get and an idea of the total time that needs for each activity, adding the calendar time in timescale is a good idea, see figure 1. Step 2 - Creating the bars: Create bars representing each activity. The length of the bars should be proportional to the duration time. If there are multiple activities it is a good idea to create a summary or hammock activity, see figure 1. By using hammock activities the project can be summarized in fewer activities, which gives a better overview of the project, but in the same time, you can still go into the level of detail with the activity group in the hammock. The bar of the hammock activity begins when the earliest activity in the group starts and end when the latest activity in the group ends, see figure 2. Figure 2: How to create a Gantt chart. Reproduced from: [4] Step 3 - Revise til Gantt chart: Have a look at the Gantt chart again. Are all the important activities there and are they logically placed in the chart? What about the timescale? Are the durations reasonable? Make the necessary changes in the chart.

Critical path method (CPM)

What is the Critical path method

Develop in the 1950s by Morgan R. Walker and James E. Kelley. CPM is very similar to PERT(Program evaluation and review techniques), but represent information in a different way.

Definition

"A schedule network analysis technique used to determine the amount of scheduling flexibility (the amount of float) on various logical network paths in the project schedule network, and to determine the minimum total project duration. Early start and finish dates are calculated by means of a forward pass, using a specified start date. Late start and finish dates are calculated by means of a backward pass, starting from a specified completion date, which sometimes is the project early finish date determined during the forward pass calculation.”

CPM vs. PERT

What is the difference between CPM and PERT?

How to create the Critical path method

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Creating a Gantt chart step by step

Step 1 - Specify each activity: All activities need to be specified. The activities are usually drawend from the work breakdown structure. Step 2 - Sequence the activities: The understanding of the dependencies of the activities is important when creating a critical path method. Therefore you should make a table describing which activities are affecting which. Step 3 - Creating a Network Diagram: Dummi activities caption Step 4 - Estimate activity durations: Step 5 - Identyfy the critical path: Step 6 - Use and update:

Constructing a Network Diagram

Checklist when creating a Network Diagram
1. 2.

The Importance of the Gantt Chart and the Critical Path for Project Management

Pros and cons

	Pros	Cons
Gantt chart	An easy way to schedule all tasks and track them in the project progress next to the deadline(s) Strong visual communication and scheduling tool Readable for the stakeholders.	Does not show the dependency of the tasks to each other Does not show which tasks are ‘critical’ to finish the project on time. Constant updates of the chart
CPM	Identifying critical activities	more...