Types of S-curves Target S-curves
Following Project commencement, the Project's schedule will usually require changes. As the Baseline Schedule should not be changed once the Project has commenced, these changes are instead made to the Production Schedule. The Production Schedule is created by making a copy of the Baseline Schedule. If the Baseline Schedule was baselined, the Production Schedule will include Baseline dates and values for the original Tasks as well as their planned production dates and values.
The Production Schedule reflects the actual progress of the Project to date (Task % Complete to date), any Tasks added to and/or removed from the Project, any revisions made to Tasks yet to commence or not yet finished, as well as actual dates and values for Tasks that are ongoing or have finished.
Tasks that do not contain valid Start Dates and/or Finish Dates, and/or zero quantities for Man Hours and/or Cost cannot be used to generate S‑curves. So it is important to note that the Production Schedule must contain valid dates and values for all Tasks, regardless of whether the Task has commenced or not.
Originally these Task dates and values will be the same as the Baseline Schedule (provided the Baseline Schedule was baselined, and copied to create the Production Schedule). Task dates and values may be amended as required using actual values (such as when the Task actually started, finished, Man Hours / Cost actually expended, etc.) or estimated dates and values for Tasks that are yet to commence or have not yet finished.
The Production Schedule may be used to generate Target S‑curves, as well as the original Baseline S‑curves if it contains Baseline data. The Target S‑curves reflect the progress of the Project if all Tasks are completed as currently scheduled.
In an ideal world, the Target S-curves will meet the Baseline S‑curves at the completion of the Project (On Time, On Budget) or finish below and to the left of the Baseline S‑curves (Finished Early, Under Budget). In reality, it is not uncommon for the Target S‑curves to finish above and to the right of the Baseline S‑curves (Finished Late, Over Budget). The Target S‑curves will usually change over the duration of the Project due to changes to Task Start Dates and Finish Dates, Man Hours, and/or Cost.
Figure 2: Target S-curve (showing Baseline S-curve for comparison)