GANNT charts are simply bar code charts that show the progress of tasks within the larger project along with who is assigned to each. PERT charts are flow charts originally designed by the US Navy that arrive at similar outcomes albeit using a flow chart procedure. In short, using spreadsheets and graphing helps a team to see the big picture as progress is made (or not made) toward goals. One cannot argue with a bar graph or a trend-line base on real empirical data.