The S-curve envelope as a tool for monitoring and control of projects

Monitoring and controlling the progress of projects is always indispensable to project manager's mission because it can help to produce updated pictures of how the project is progressing. Even with a target progress derived from a detailed project schedule, the actual progress, under the influence of many factors, may deviate significantly from the target, which requires to take corrective actions/control. A project monitoring and control system must provide the required information to answer the following questions: What is the difference between the planned and actual work performance? How is the project progressing in terms of completion of activities? How much ahead or behind schedule is the project? What is the efficiency of the time utilized on the project? In this paper, the concept of S-curve envelope is introduced. This S-curve envelope consists of two curves. The upper curve corresponds to the curve of the earliest times whereas the lower curve corresponds to the curve of the latest times. This S-curve envelope can be used as an early warning system to determine whether the S-curve from the actual progress data is reasonable or needs to be revised. If, when comparing the S-curve based on actual progress to the scheduled-based S-curve envelope, the project is running outside the envelope, appropriate action must be taken depending on whether the actual S-curve is below or above the envelope.